Minims

MINING

THE art of mining consists of those processes by which useful minerals are obtained from the earth’s crust.

This definition is wider than what is popularly known as mining, for it includes not only underground excavations but also open workings; at the same time it excludes underground workings which are simply used for passages, such as railway tunnels and sewers, and galleries for military purposes. We must remark also that the word “mine,” or its equivalent in other languages, varies in signification in different countries on account of legal enactments or decisions which define it. Thus, in France and Belgium, the workings for mineral are classified by the law of 1810, according to the nature of the substance wrought, into mines, minières, et carrières. In the United Kingdom, on the contrary, it is the nature of the excavation which decides the question for certain legislative purposes, and the term mine is restricted to workings which are carried on underground by artificial light. The consequence is that what is merely an underground stone quarry in France becomes a true mine in England, whilst the open workings for iron ore, such as exist in Northamptonshire, would be true mines under the French law. It is necessary, therefore, in an article on mining, to go beyond the English legal definition of a mine, and include the methods of working minerals in excavations open to daylight as well as in those which are purely subterranean. Furthermore, as it is customary for the miner to cleanse his ore to a greater or less extent before selling it to the smelter, we shall treat, under the head of mining, those processes which a·re commonly known as the dressing or mechanical preparation of ores; and, finally, a few remarks will be made concerning legislation affecting mines in the United Kingdom, accidents in mines, and the production of the useful minerals in various parts of the globe.

The subject therefore will be dealt with as follows :—

1. Manner in which the useful minerals occur in the earth’s crust, viz., tabular deposits and masses; faults or dislocations.

2. Prospecting, or search for mineral.

3. Boring with rods and ropes; diamond drill.

4. Breaking ground; tools employed; blasting by various methods; machine drills; driving levels and sinking shafts.

5. Principles of employment of mining labour.

6. Means of securing excavations by timber or masonry.

7. Exploitation, or the working away of strata or veins.

8. Carriage or transport of minerals through underground roads.

9. Winding, or raising in the shafts, with the machinery and apparatus required.

10. Drainage of mines, adit-levels, pumps, pumping engines.

11. Ventilation and lighting of mines.

12. Means of descending into and ascending from mines.

13. Dressing or mechanical preparation of minerals.

14. Recent legislation affecting mines in the United Kingdom.

15. Accidents in mines.

16. Useful minerals produced in various parts of the globe.

1. Manner in which the Useful Minerals Occur.— The repositories of the useful minerals may be classified according to their shape as (A) tabular deposits, and (B) masses.

A. Tabular Deposits.— These are deposits which have a more or less flattened or sheet-like form. They may be divided, according to their origin, into (1) beds or strata, and (2) mineral veins or lodes.

(1) Beds.— Geology teaches us that a large proportion of the rocks met with at the surface of the earth consist of substances arranged in distinct layers, owing to the fact that these rocks have been formed at the bottom of seas, lakes, or rivers by the gradual deposition of sediment, by precipitation from solutions, and by the growth or accumulation of animal and vegetable organisms. If any one of these layers consists of a useful mineral, or contains enough to make it valuable, we say that we have a deposit in the form of a bed, stratum, or seam. Of course the most important of all bedded or stratified deposits is coal, but, in addition, we have beds of anthracite, lignite, iron ore, especially in the Oolitic rocks, cupriferous shale, lead-bearing sandstone, silver-bearing sandstone, diamond-, gold-, and tin-bearing gravels, to say nothing of sulphur, rock-salt, clays, various kinds of stone, such as limestone and gypsum, oil-shale, alum-shale, and slate.

The characteristic feature of a bed is that it is a member of a series of stratified rocks; the layer above it is called the roof of the deposit, and the one below it is the floor. Its thickness is the distance from the roof to the floor at right angles to the planes of stratification; its dip is the inclination downwards measured from the horizontal; its strike is the direction of a horizontal line drawn in the middle plane.

The thickness of beds that are worked varies within very wide limits. Whilst the thickness of certain workable beds of coal is only 1 foot, and that of the Mansfeld cupriferous shale only 10 to 20 inches, we find on the other hand one of the beds of lead-bearing sandstone at Mechernich no less than 85 feet thick, and beds of slate far exceeding that thickness. It must not be supposed, however, that the thickness of a bed necessarily remains uniform. Occasionally this is the case over a very large area; but frequently the thickness varies, and the bed may dwindle away gradually, or increase in size, or become divided into two owing to the appearance of a parting of valueless rock. Fig. 1 shows beds of shale, limestone, iron ore, and sandstone. Any one of these beds may be valuable enough to be worked.

(2) Mineral Veins or Lodes. —Veins or lodes are tabular or sheet-like deposits of mineral which have been formed since the rocks by which they are surrounded; they differ, therefore, by their subsequent origin from beds, which, as just stated, are of contemporaneous origin with the enclosing rocks (although of course cases occur in which the deposit is lying unconformably upon very much older strata, or is covered unconformably by very much younger strata). It is necessary to explain that the term “vein” in this definition is used in a more restricted sense than is sometimes customary among miners, who speak of veins of coal, clay-ironstone, and slate, which geologically are true beds. They see a band of valuable mineral or rock, and, careless of its origin, call it metaphorically a vein or seam. On the other hand, the definition is broader than that which prevails among some geologists, who would confine the term vein to deposits occupying spaces formed by fissures.

The term “lode” was defined in 1877 by Mr Justice Field in the celebrated Eureka v. Richmond case as follows:—“We are of opinion, therefore, that the term, as used in the Acts of Congress, is applicable to any zone or belt of mineralized rock lying within boundaries clearly separating it from the neighbouring rocks.” This interpretation seems suitable for the peculiar mining tenure of the United States, where the discoverer of a vein or lode can obtain a mining claim of 500 yards in length along the lode. It protects the prospector, whose object is to obtain a secure title, the mode of origin of the deposit being a matter of small importance to him so long as it is worth working. In many cases also it would be impossible to decide upon the mode of origin until workings had progressed considerably, and even then there would be room for disputes.

No doubt a very large number of mineral veins are simply the contents of fissures; others are bands of rock impregnated with ore adjacent to fissures or planes of separation; others, again, have been formed by the more or less complete replacement of the constituents of the original rock by particles of ore.

Veins may occur in igneous or in sedimentary rocks, and in the latter they frequently cut across the planes of stratification.

Like a bed, a vein has its dip and strike; but, as the dip of veins is generally great, the inclination is usually measured from the vertical, and is then spoken of as the τ<,nderlie or hade. The bounding planes of a vein are called the walls or cheeks, and they are frequently smooth and striated, showing that one side must have slid against the other. The upper wall is known as the hanging wall, the lower one aS the foot wall. The width of a vein is measured at right angles to the walls.

A typical example of a fissure-vein is shown in fig. 2, representing a lead lode in slate at Wheal Mary Ann mine in Cornwall.

It is evident that a fissure in the surrounding slate has here been filled up by the successive deposition of bands of mineral on both sides.

A large proportion of the contents of a lode may consist of fragments of the walls that have fallen into the original fissure, and these are often tightly cemented together by minerals that have been introduced subsequently. The horizontal section of part of the Comstock lode (Plate IV.) shows much “country” rock enclosed within the walls.

Where a lode consists of rock impregnated with ore, the mineralized. part may fade away gradually into the surrounding rock (country) without there being any distinct wall, as shown in fig. 3, which is an illustration taken from the Great Flat Lode near Redruth in Cornwall.

The celebrated Ruby Hill deposit in the Eureka district, Nevada, is a mineralized zone of dolomitic limestone varying in width from a few inches to 450 feet, and having a mean width of 250 feet. It contains numerous irregular ore-bodies, which consist mainly of highly ferruginous carbonate of lead, rich in silver and gold. This mineralized limestone band, long called a lode by miners, has been determined by the decision just mentioned to be a lode in the eyes of the law.

Veins often continue for a great distance along their strike. The Van lode in Montgomeryshire is known for a length of 9 miles, whilst the Great Quartz Vein in California has been traced for a distance of no less than 80 miles. Veins are of less uniform productiveness than beds, and are rarely worth working throughout. Rich portions alternate with poor or worthless portions. The rich parts have received various names according to the forms they assume: fig. 4 represents a longitudinal section along the strike (course) of a lode, and the stippled parts are ore-bodies; B, B, B are bunches; A is a large bunch or course of ore ; when an ore-body forms a sort of continuous column we have a shoot, and ore-bodies which on being excavated leave chimney-like openings are called pipes (fig. 4, C). In the United States the Spanish word bonanza, literally meaning “fair weather” or “prosperity,” is frequently used for a rich body of ore.

The richness of veins is dependent in many cases upon the nature of the adjacent rock (country), upon the underlie, and upon the strike, variations in any one of these three elements being often sufficient to cause a decided change of productiveness.

Various theories have been formed concerning the origin of mineral veins. Some geologists suppose that the minerals now constituting the veinshave been dissolved out of the adjacent rocks and re-deposited in the vein cavity; others, on the contrary, believe that the ores have been brought up from great depths by mineral springs. In all probability both theories are correct, some lodes having been formed by the former process and some by the latter; and, furthermore, other lodes appear to owe their origin to a gradual substitution of valuable minerals in the place of some of the constituents of a worthless rock. One of the most important contributions to the science of ore-deposits of late years has been the discovery by Professor F. Sandberger of small quantities of silver, lead, copper, nickel, cobalt, bismuth, arsenic, antimony, and tin in silicates, such as oUvine, augite, hornblende, and mica, which are constituents of igneous rocks. He therefore regards these rocks as the sources ιrom which lodes have derived their riches.

B. Masses.— These are deposits of mineral, often of J irregular shapes, which cannot be distinctly recognized as beds or veins. Such, for instance, are the red haematite deposits of the Ulverston district (fig. 5) and the brown haematite deposits (churns) of the Forest of Dean, which occupy irregular cavities in the Mountain Limestone. These may have been formed by the percolation of water bringing down iron in solution from overlying Triassic rocks. Other examples of masses are the calamine deposits of Altenberg (fig. 6), Sardinia, and Lombardy, the iron ore deposits in Missouri, such as Iron Mountain and Pilot Knob, the huge upright “necks” or “pipes” of diamantiferous rock in South

Africa, and the granite decomposed in situ worked for china clay in Cornwall.

Under this head also are included by most authors the so-called “stockworks” or “reticulated masses,” names applied to masses of sedimentary or igneous rock which are penetrated by so many little mineral veins as to make the whole worth excavating.

It must be understood that we cannot expect nature to make distinct lines of demarcation between the different kinds of deposits. Though we may be able to see clearly that a seam of coal is contemporaneous with the enclosing rocks, and that a vein intersecting beds of shale and sandstone was formed subsequently, cases frequently occur where the origin of the mineral is uncertain. For example, we have the lead-bearing sandstone of Mechernich and the silver-bearing sandstone of Utah. The grains of sand are of sedimentary origin; but opinions differ as to whether the lead and silver respectively were deposited with the sand or were introduced subsequently by solutions percolating through the beds. In the case of the well-known bed of Cleveland ironstone, Dr Sorby considers that the iron was “derived partly from mechanical deposition and partly from subsequent chemical replacement of the originally deposited carbonate of lime.” Furthermore, a bed may be so folded and contracted as to lose its original sheet-like form in places and assume the shape of an irregular mass. This may happen even with a coal seam.

All kinds of deposits are subject not only to irregularities of origin dependent upon their mode of formation but also to dislocations or shiftings known as faults, heaves, or throws.

We will take the case of a bed (fig. 7). AB is a seam λvhich ends off suddenly at B, whilst the continuation is found at a lower level at CD. The bed was evidently once continuous; but a fracture took place along the line XY followed by a displacement. As a rule the portion of rock on the hanging-wall side of a fault appears to have slid downwards, but occasionally this is not so, and we have a reversed fault (fig. 8). It is very evident, in some cases, that the motion took place, not along the line of greatest dip, but in a dia gonal direction, causing a displacement sideways as well as downwards. Nevertheless, where beds or veins are not horizontal, a mere shift along the line of dip is sufficient to cause an apparent heave sideways. This will be understood from fig. 9. Let AB and CD represent two portions of a lode dislocated by the fault EF. The point B' corresponded originally with B, and the dislocation was caused by a simple sliding of B ’ along the line of dip BB'.

An instance of the complication caused by a succession of faults is shown in fig. 10.

2. Prospecting, or Search for Mineral.— The object of the prospector is to discover valuable deposits of mineral. This search is beset with many difficulties: the outcrops of mineral deposits are frequently hidden by soil; the nature of the deposit itself is generally entirely changed near the surface; and, in addition to this, the explorer may have to pursue his work in trackless forests far away from any settlements.

The prospector seeks for natural sections of the rocks, such as occur in cliffs or in river valleys and their tributary gullies and gorges; he examines the materials constituting the river-beds, often digging up and washing portions in a pan, in order to ascertain whether they contain traces of the heavy ores or metals. If, while prospecting in a valley, he discovers stones that have the appearance of having once belonged to veins, he endeavours to trace them to their source, and is perhaps rewarded by finding similar fragments, but less water-worn, as he goes up the stream; further on he may come upon large blocks of veinstuff lying about, and finally find the vein itself laid bare in a gorge, or at the bottom of a brook, or possibly projecting above the soil in the form of huge crags of quartz. Thus at the Great Western quicksilver mine in California the outcrop of the vein appears as a dike over 100 feet wide, and having precipitous sides in places 75 feet high. Loose pieces of veinstuff found lying about are known in Cornwall as shoad-stones, and shoading is the term given to the process of tracking them to the parent lode.

The upper portion of a deposit is frequently much altered by atmospheric agencies, and bears little resemblance to the undecomposed bed or vein which will eventually be met with at a greater or lesser depth. The principal difference consists in the change of sulphides into oxides or oxidized compounds. Thus iron pyrites, which is such a common constituent of mineral veins, is converted into hydrated oxide of iron, and a vein originally consisting largely of iron pyrites and quartz now becomes a cindery mixture of quartz and ochre, known in Cornwall as gossan. This gossan, or iron hat, may often furnish important indications concerning the nature of the lode itself, because such minerals as pyromorphite or cerussite point to the existence of galena, whilst melaconite, cuprite, malachite, and azurite are the forerunners of chalcopyrite or copper glance. The gossan itself may contain a sufficient quantity of valuable ores to be worth working.

The seams containing native sulphur in Sicily often show no trace of that element immediately at the surface, as the sulphur-bearing limestone weathers into a soft white granular or pulverulent variety of gypsum, called briscale by the miners, and considered by them as affording important indications concerning the bed itself.

Other signs of mineral deposits are given by springs and by certain plants dependent upon the deposit or its associated minerals for part of their nourishment. The appearance of the so-called lode-lights may be explained by the production of phosphoretted hydrogen from the action of organic matter and water upon phosphates, which are so common in the upper parts of mineral veins; and one hears also of differences in the appearance of the vegetation along the line of the deposit, of places where snow will not lie in winter, and of vapours hanging over the ground. Though some writers refuse to put any value upon these indications, they should not be entirely overlooked, because the outcrop of a lode, of different nature and texture to the surrounding rocks, and which is generally a channel for water, may readily cause the phenomena just mentioned. Where the surface is cultivated and the natural springs are tapped by adit-levels or other mine-workings, these appearances cannot be looked for to any great extent. With one special mineral, magnetic iron, the position of the deposit may be traced out with some degree of accuracy with a dipping needle; this is used in Sweden.

After having acquired an idea of the position of a vein or seam by some of the surface indications just mentioned, it is necessary, before attacking it by shafts or levels, to obtain more certain data concerning it. In the case of mineral veins, trenches are dug at right angles to the supposed strike; and, when the upper part of the deposit has been cut in several places, its general course and dip can be determined sufficiently for the purpose of arranging the future workings. These trenches are called “costean pits”; in some cases, instead of a trench, a pit is sunk a short distance and a little tunnel driven out.

Where the mineral to be wrought occurs as a bed or mass, the process of boring is resorted to, and indeed this method is also applied in the case of veins, especially in the United States. Boring is a work of such importance that it deserves to be treated under a separate heading.

3. Boring with Rods and Ropes—Diamond Drills.— The object of boring is to reach a deposit by a small hole and ascertain its nature, its depth from the surface, thickness, dip, and strike. Bore-holes are also used for obtaining water, brine, and petroleum, which either rise to the surface or have to be pumped up from a certain depth, and finally for tapping water in old workings or for effecting ventilation. The methods of boring may be classified as follows :—(1) boring with the rod; (2) boring with the rope; (3) boring with the diamond drill.

In the first method tools for cutting and removing the rock are fixed to rods, which are lengthened as the hole increases in depth, and which are worked by hand or by machinery at the surface. Where the ground is soft, such as sand or clay, tools like augers can be employed; but in harder ground it becomes necessary to have recourse to percussion; various forms of chisel are used, the simplest being made of the shape shown in fig. 11. The rods generally consist of bars of square iron, from 1 inch to 2 inches on the side. The length of each rod depends upon the height of the tower, derrick, or shears erected above the bore-hole, which should be an exact multiple of the individual parts.

These are made in lengths of 15 to 30 or rarely 40 feet, and with a suitable tower it is possible to detach or attach two or three lengths at a time, instead of having to make or unmake eveιy joint. The mode of connexion usually preferred is by a screw joint as shown in fig. 12; care is taken to have all the joints exactly alike, so that any two bars can be screwed together. In order to diminish the weight of the rods, which becomes consider able in deep holes, wood has sometimes been employed. The rods are connected by male and female screws attached to the rods by sockets of sheet iron, or by a fork-like arrangement. At the surface a head is screwed to the uppermost rod by which the rods can be lifted, and they are turned by means of cross-bars called tillers.

When the depth is small the rods are lifted by hand and then allowed to drop, being turned slightly at each lift so that the cutting chisel may strike a new place each time. For greater depths a lever has to be employed, the rods being suspended at one end, whilst the other end can be pressed down by men using their hands or feet. The spring pole is another arrangement, in which the elasticity of a long pole is made use of for lifting the rod at each stroke. The length of the stroke can be maintained the same while the bore-hole is deepened by means of a screw in a swivel-head at the top of the rod.

With deep holes, and especially those of large diameter, steam machinery has to be employed for working the rod; the engine may be direct-acting and stand immediately above the bore-hole, but a commoner arrangement is to employ a single-acting cylinder working a beam. Occasionally also the beam is actuated by a connecting-rod worked by a crank.

The actual boring machinery has now been described, and the mere boring appears to be a very simple matter, consisting only in lifting the rod a little and allowing it to drop, the rod being turned slightly before each stroke. Nevertheless the process of putting down a bore-hole is not so simple as it seems, for there are numerous indispensable accessory operations which take up much time. In the first place the débris have to be removed, and in order to effect this the rods must be drawn up, the swivel-head is disconnected and a cap screwed on. A length of rods is now drawn up by a hand or steam windlass and disconnected. It is well to have as many caps as there are lengths to be drawn up, and then each length can be suspended in the house. Sometimes a grip which catches the rod at the bulging joint is used instead of a cap. The next operation consists in lowering by means of a rope the shell-pump or sludger, which is a hollow cylinder with a clack or a ball-valve (fig. 13). It is worked up and down a little till it is filled, and it is then drawn up and emptied at the surface. The operation h repeated, if necessary, and the boring is resumed with the rod.

Occasionally a bore-hole has to be widened slightly with a tool called a reamer. Soft beds may have to be bored through with a wimble ; and, unless the rocks are hard and firm, the hole has to be lined with a tube, generally of sheet-iron. Accidents may occur, causing an immense amount of trouble, such as the breaking of rods or chisel, and many ingenious implements have been devised for seizing the broken rod or the fragments of tools which prevent further progress with the work.

In boring at considerable depths, the weight of the rod becomes so great that much vibration ensues when the mass is suddenly arrested by the chisel striking against the bottom of the hole. Various devices have been contrived for overcoming this difficulty and producing a tool which will act independently of the rod. One of the best-known arrangements is the free-falling tool invented by Kind (fig. 14). The head of the actual boring-rod is held by a click or grapple; when the main rod descends, the resistance of the water in the hole slightly stops the sliding disk D, the jaws J, J open, the head is disengaged, and the boring part falls and strikes the bottom without any injurious vibrations being communicated to the main rod. When this descends farther the head is caught again by the click. Special tools also are used for cutting an annular groove at the bottom of a bore-hole and breaking off the core, which is then brought up, with certain precautions, so as to show the nature and dip of the strata traversed.

In order to obviate the great loss of time which ensues from connecting and disconnecting long lengths of rods, recourse may be had to boring with the rope. In this method, known as the Chinese method, the chisel is worked by a rope in the same manner as the sludger already described. Messrs Mather and Platt of Manchester have long used with success, in many parts of England and various other countries, a system of boring by means of a flat hempen rope.

The most important modification of late years in the process of making bore-holes is the introduction of the diamond drill. The working part of the drill consists of the so-called crown, which is a short piece of tube made of cast steel, at one end of which a number of black diamonds are fastened into small cavities (fig. 15). The crown is screwed on to wroughtiron pipes, which constitute the boring rod. Machinery at the surface causes the rod to rotate, and the result is the cutting of an annular groove at the bottom of the hole, leaving a core, which, breaking off from time to time, is caught by a little shoulder, and brought up to the surface with the rod. In places where it is not necessary to make any verification of the rocks traversed, the crown is arranged with diamonds in the centre also. The débris, in either case, are washed away by a stream of water, which is forced down the tube and flows up the sides of the hole. With this system a bore-hole can be deepened continuously at a speed altogether unattainable by the other methods, which require stoppages for cleaning out. It has the further advantage of making it possible to drill holes in any direction; and prospecting diamond drills are constantly used with much success inside many metal mines, especially in the United States.

Fig. 16 shows the Little Champion Rock-Drill,which is largely employed in the Lake Superior district for prospecting. It can be used above or below ground. Two inclined cylinders drive a horizontal crank shaft, which works bevel gear, causing the drill to revolve. At the same time a countershaft is likewise set in motion, and this effects the advance of the drill by gearing driving the feed-screw; as there are three kinds of gearing, the speed can be varied at pleasure. The feed-screw and its connexions are carried by a swivel-head, and this can be turned so as to drill holes at an angle. The drum shown above the cylinders is used for hoisting out the drill-rods by a rope. The rods are lap-welded iron tubes 1⅞ inches in diameter, fitted with a bayonet joint.

Another light portable prospecting drill for underground work is represented in fig. 17. It is intended for drilling holes 1∣ inches in diameter to a depth of 150 feet. The cores which it yields are ⅜ inch in diameter. It has double oscillating cylinders 3⅛ inches in diameter with 3⅛ inches stroke, which are run up to a speed of 800 revolutions. The drill can be set to bore in any direction by turning the swivel-head on which it is carried.

The larger rock-drill used by the American Diamond Rock Boring Company for putting down holes to a depth of 2000 feet consists of a 20 horse-power boiler with two oscillating 6-inch cylinders and the necessary gearing for working the drill, all mounted upon a carriage, so that the whole machine is readily moved from place to place. The feed is effected by gearing or by hydraulic pressurera 2∣-inch crown is employed, leaving a 2-inch core. Each separate drill-rod is 10 feet long. The total weight of the machine is about 4 tons.

4. Breaking Ground — Tools Employed — Blasting ^by Various Methods—Machine Drills—Driving Levels and Sinking Shafts.— The kind of ground in which mining excavations have to be carried on varies within the widest limits, from loose quicksands to rocks which are so hard that the best steel tools will scarcely touch them.

Loose ground can be removed with the shovel; but in the special case of peat sharp spades are employed, which cut through the fibres and furnish lumps or sods of convenient form for drying and subsequent use as fuel. What is called fair, soft, or easy ground, such as clay, shale, decomposed clay-slate, and chalk, requires the use of the pick and the shovel. The pick is a tool of very variable form, according to the material operated on. Thus there are the navvy’s pick, the single-pointed pick with a striking head at the other end called the pollpick (fig. 18), and numerous varieties of the double-pointed pick (fig. 19), the special tool of the collier, but also largely used in metal mining. When the ground, though harder, is nevertheless “jointy,” or traversed by many natural fissures, the wedge comes into play. The Cornish tool known as a gad is a pointed wedge (fig. 20). The so-called “pick and gad” work consists in breaking away the easy ground with the point of the pick, wedging off pieces with the gad driven in by a sledge or the poll of the pick, or prizing them off with the pick after they have been loosened by the gad. The Saxon gad is held on a little handle, and is struck with a hammer. It is used for wedging off pieces of jointy ground, and in former days even hard rocks were excavated by its aid. The process consisted in chipping out a series of parallel grooves and then chipping away the ridges left between the grooves. As a method of working this process is obsolete; but it is useful on a small scale for cutting recesses (hitches) for timber, for dressing the sides of levels or shafts before putting in dams, and for doing work in places where blasting might injure pumps or other machinery.

We now come to hard ground; and in this class we have a large proportion of the rocks met with by the miner, such as slate of various kinds, hard grits and sandstone, limestone, the metamorphic schists, granite, and the contents of many mineral veins. Rocks of this kind are attacked by boring and blasting. The tools employed are the jumper, the borer or drill, the hammer, the sledge (mallet, Cornwall), the scraper and charger, the tamping bar or stemmer, in some places the pricker or needle, the claying bar, the crowbar, and finally the shovel for clearing away the broken rock.

The jumper (fig. 21) is merely a long bar of iron terminating in two chisel-like edges made of steel; generally there is a swelling in the middle, and sometimes the jumper tapers all the way from the middle to the edge or bit. The jumper is most commonly used when it is necessary to bore holes downwards, and is largely employed in quarries; occasionally it is used in boring holes horizontally, as for instance in the salt mines of Cheshire. The jumper is held in the desired direction, lifted up, and thrust down; it is turned a little after each stroke.

However, the miner’s tool is generally the borer proper, or drill (fig. 22), which is a bar of round or octagonal steel, usually from ∣ inch to 1 j inches in diameter, with one end forged into a chisel-shaped edge, the exact shape and degree of sharpness varying according to the hardness of the rock. The hole is bored by striking the drill with a hammer or sledge and turning it after each blow. Boring is said to be single-handed if the miner holds the drill in one hand and strikes with the hammer in the other, whilst it is called double-handed when one man turns and another strikes. The hammers for single-handed boring usually vary in weight from 2 to 6 or 7 ft).

The double-handed boring hammer, or sledge (fig. 23), weighs from 6 to 10 ft> or more. If a hole is directed downwards, the miner pours in a little water and bores the hole wet. From time to time he draws out the sludge with the scraper, a little disk at the end of a metal rod, and he takes a fresh borer when the tool he is using has become blunt. The depth bored varies with the rock and the nature of the excavation; but in driving levels in the ordinary way the depth is commonly from 18 inches to 3 feet.

Holes for blasting are sometimes bored by tools like carpenters’ augers. One of the simplest, which is used in some French slate-mines, is very like a brace and bit, and the tool is kept pressed against the rock by means of a screw fixed in a frame resting on the ground.

The pricker, or needle, is a slender tapering rod of copper or bronze, with a ring at the large end. It is used for maintaining a hole in the tamping through which the charge can be fired. The use of needles made of iron is prohibited in many countries, on account of the danger of their striking sparks which might fire the charge. The tamping bar, or stemmer, is a rod of iron, copper, or bronze, or iron shod with copper, and it is used for ramming in dried clay, slate pounded up, or other fine material, upon the powder, and so creating a resistance sufficient to make the gases generated by the explosion of the charge rend the rock in the manner required. The claying bar is used for lining wet holes with clay, and so rendering them temporarily watertight.

Shovels vary much in different districts. In the southwest of England the long-handled shovel is preferred to the common one with a short handle; in Germany the ore or rubbish is frequently scraped into a tray with a sort of hoe.

In addition to these tools the miner requires an explosive, and a means of firing the charge at the bottom of the hole which will give him time to escape. Twenty years ago gunpowder was the only explosive in common use in mines, but at the present day its place has been taken to a very large extent by mixtures containing nitro-glycerin or gun-cotton. The powder used for blasting in mines usually contains less saltpetre than that which is employed for sporting or military purposes. The following is an analysis of mining powder by Captain Noble and Sir F. Abel: — [table]

Gunpowder compressed into cylinders of diameters suitable for bore-holes, and provided with a central hole for the insertion of the fuse, has lately been brought forward with some success.

Nitro-glycerin or glyceryl nitrate is a light-yellow oily liquid which is very sensitive to shocks; under the action of a fulminating cap it explodes with great violence. Its chemical composition is expressed by the formula C 3 H 5 (NO 2 ) 3 O 3 or (C 3 H s )3NO 3 j its specific gravity is 1 ’ 6. It has been found so dangerous that its use by itself has been given up; but on the other hand the mixture of nitro-glycerin and infusorial earth (Kieselguhr') called dynamite or giant powder is now one of the commonest explosives met with. It has the advantage over powder that it is far more powerful, that it may be used in wet holes or under water, that it is very effective even in ground full of “vughs” or cavities, and that it requires no hard tamping, which is always a source of danger. Its plasticity too enables it to fill the space at the bottom of a bore-hole, which is rarely a true cylinder, more completely than any solid cartridge can do. One disadvantage is that it has to be thawed in cold weather, and there is also the fact that occasionally the whole of a charge of dynamite fails to go off, and unnoticed remnants have exploded and caused serious and even fatal accidents when struck with the pick or borer. The danger is enhanced when the remnants have been left in contact with water, which causes a separation of the sensitive nitro-glycerin, so that even a blow upon the adjacent rock may lead to an accident if any of the explosive oil has leaked into cracks. The strongest dynamite contains about 75 per cent, of nitroglycerin, the rest being kieselguhr. A newer explosive is blasting gelatin; it is made by mixing nitro-cotton with nitro-glycerin, until enough nitro-cotton has been dissolved to convert the nitro-glycerin into a jelly-like mass. The blasting gelatin in ordinary use contains no less than 93 per cent, of nitro-glycerin, with 7 per cent, of nitro-cotton, and its strength is very great.

Gun-cotton per se is not much in favour in ordinary mining; but mixed with some nitrate or mixture of nitrates, such as the nitrates of barium and potassium, and known as cotton powder, tonite, and potentite, it is employed extensively. Though not quite so powerful as dynamite, nitrated gun-cotton possesses the important advantage of not requiring to be thawed in cold weather. As in the case of dynamite, accidents have been caused by remnants of charges; and with both explosives it is necessary to examine carefully the bottoms of all holes after blasting, and to destroy any possible remnants by firing off a detonator in any bottom or “socket” which cannot with certainty be pronounced free from danger.

The commonest method of firing a charge is by means of the safety-fuse, a cord containing a core of gunpowder introduced during the process of manufacture; it may be rendered waterproof by tar or gutta-percha.

In blasting in the ordinary way the charge of gunpowder is put in either loose or enclosed in a paper bag, and it is pressed down to the bottom of the hole with a wooden stick, whilst a piece of fuse also is inserted extending from the charge well beyond the hole. If the powder is loose the miner carefully wipes down the sides of the hole with a wet swab stick (a wooden rod with the fibres frayed at one end), or with a wisp of hay twisted round the scraper, in order to remove any loose grains adhering to the fuse or the sides of the hole, and then presses in a wad of hay or paper. A little fine tamping, often the dust from boring a dry hole, is now thrown in and rammed down with the wooden charging stick, and the same process is repeated, and when harder tamping is required the metal bar is brought into operation, until the hole is completely filled.

As the safety fuse burns slowly, at the rate of about 2 or 3 feet a minute, the miner can secure ample time for retreat by taking a sufficient length. It is usual to ignite the fuse by a candle-end fixed under it by a piece of clay, and it takes a little ^nιe for the candle to burn through the fuse.

The old plan of firing a charge, which is still in use in many places, consists in inserting the needle into the charge and then tamping up the hole. Care is taken to draw out the needle a little as the tamping proceeds, so as to prevent too much force being required for its final withdrawal. The small hole left in this way serves for the insertion of a straw, rush, or series of small quills, filled with fine powder, which like the fuse reaches from the charge to the outside. A short squib which shoots a stream of sparks down the needle hole is also used occasionally. The straw or squib is lighted by some kind of slow match, made either by dipping a cotton strand in melted sulphur or soaking a piece of paper or a lucifer in the tallow of a candle; touch-paper also is used.

Dynamite, blasting gelatin, gun-cotton, and cotton-powder are fired by the detonation of a fulminating cap. A long copper cap containing fulminate of mercury is fastened into the safety-fuse by squeezing with a pair of nippers, and is then inserted into a small cartridge of the explosive {primer), and placed above the rest of the charge. Fig. 24 shows a hole charged with two dynamite cartridges, a primer with cap, and filled up with water as tamping. Sometimes gun-cotton is fired by a small charge of powder above it.

Several substitutes for explosives have been tried with the object of getting rid of the flame, which is dangerous in collieries giving off firedamp. Among these may be mentioned plugs of dry wood which swell when wetted, wedges worked by hydraulic pressure, cartridges containing compressed air at extremely high pressures, and lastly cartridges of compressed lime which expands when water is brought into it.

For the purpose of firing several holes simultaneously, Messrs Bickford, Smith, & Co., the original inventors and makers of the safety-fuse, have brought out a new fuse (fig. 25), the action of which will be easily understood from the figure. An ordinary fuse is fixed into a metal case called the igniter, from which a number of instantaneous fuses convey fire to as many separate holes. It is found in practice that this fuse answers very well.

Charges may be readily fired singly or simultaneously with the aid of electricity, either of high tension obtained from a frictional, magneto-electric, or dynamo-electric machine, or of low tension from a galvanic battery. The former is preferred.

Fig. 26 shows a section of one of Brain’s high-tension fuses. A is a cylindrical wooden case containing a paper cartridge B, with an electric igniting composition C at the bottom. Two copper wires D, D enclosed in gutta-percha E, E reach down to the composition, where they are about - 5 ⅛ inch apart. A copper cap or detonator G is fixed on to the small end of the wooden case. The insulated wires D, D are long enough to reach beyond the borehole. The ends of the wires are scraped bare, and one wire of the first hole is twisted together with a wire of the next hole, and so on, and finally the two odd wires of the first and last hole are connected to the two wires of a single cable, or to two separate cables, extending to some place of safety to which the men can retreat. Here the two cable wires are connected by binding screws to a frictional electrical machine or dynamo exploder. A few turns of the handle charge a condenser, and by pressing a knob or by some other device the circuit is completed and the discharge effected. The electricity passes through the fuse wires making a spark at each break, and so firing the electric igniting composition. The flame flashes through the hole H, and ignites the fulminating mercury I, the detonation of which causes the explosion of the dynamite, blasting gelatin, or tonite surrounding the cap.

One great advantage of electric firing is that the miner can retire to a perfectly safe place before attempting to explode the charge. This is important in sinking shafts, where the means of escape are less easy than in levels. A second advantage is that there is no danger of a “hang fire,” an occasional source of accidents with the ordinary safety-fuse.

One of the greatest improvements in the art of mining during the last few years has been the introduction of machinery for boring holes for blasting; most of the machines imitate percussive boring by hand, but a few rotary machines are also in use. A percussive drill or perforator consists of a cylinder with a piston to which the drill is fastened. Compressed air is made to act alternately on each side of the piston, and in this manner the drill receives its reciprocating motion. Various arrangements have been adopted for securing the automatic rotation of the drill. In some cases also the advance forward of the machine, as the hole is deepened, is also effected automatically; but in many of the best drills this work is left to the man in charge. It is impossible within the limits of this article to describe the various drills now in use, or even to make a complete enumeration of them.

The following, in alphabetical order, are the names of some of the best-known drills:—Barrow, Beaumont, Burleigh, Champion, Cornish, Cranston, Darlington, Desideratum, Doering, Dubois and François,Dynamic, Eclipse, Excelsior, Ferroux, Fröhlich, Ingersoll, Laxey, Mackean, Osterkampf, Band, Roanhead, Sandycroft, Schram. An account of two of the simplest, the Barrow and the Darlington drills, will be sufficient to give a general idea of the construction of these machines.

“The Barrow drill (fig. 27) consists essentially of a gun-metal cylinder C about 2 feet in length and 4 inches in diameter, in which works a cast-steel piston-rod D, fitted with two pistons G, about 12 inches apart, mid-way between which is the tappet, or boss, G ’. In a valve-box on the top of the cylinder is placed the oscillating slide-valve H (shown separately), hinged at Μ, which is worked by the reciprocation of the tappet G' coming in contact with its lower edges, which for this purpose are formed with two slopes at each end, as shown. It has ports corresponding with openings in the slide-valve face for admitting the fresh steam or compressed air from the inlet pipe I (fig. 28) to the ports j at each end of the cylinder, and for letting the spent or exhaust air or steam escape by the exhaust pipe J. This simple arrangement constitutes the whole valve gear of the machine.

“The borer is inserted into a hole formed in the fore end of the piston rod, and is fixed therein by means of a screw. Its rotation is effected by hand, by means of the handle D ', turning a spindle D', which is so fitted by means of the cotter d, made fast in the piston DG, and fitting in a slot in the spindle D', that the latter can slide in the piston DG, but when turned by the handle causes the piston to turn with it. The spindle D' has a pinion E gearing into the pinion F, on the adjusting and feeding screw C', so that when the piston D is turned by means of the handle D" the cylinder C is simultaneously pushed along the bed-plate A. These pinions can be easily disconnected by loosening the nut/, and thus the piston and the adjusting screw can be turned independently of one another when required.

“The borers used are respectively 1∣ inches, 1 ⅛ inches, and 1 inch in diameter, the length of the stroke 4 inches, and the maximum number of blows about three hundred per minute. The air is brought down about 400 fathoms from surface, at a pressure of 50 to 55 lb to the square inch, in wrought-iron pipes 2 inches in diameter in the shaft, and 1⅛ inches in the level, and admitted through a flexible tube into the inlet I on the left-hand side of the cylinder. The cost of the pipes is rather under 7d. a foot, or about 3s. 3d. per fathom. The air is compressed at the surface by a 14-inch compressor, worked by a 12-inch horizontal engine, capable, however, of working two machine drills. The gross weight of the machine, including the bed-plate and gudgeon, is about 115 lb.”

The method of fixing the machine for work is as follows :—“The bed-plate A of the machine is formed with a gudgeon A' which fits into, and can be adjusted to any position in, a socket formed in or on a clamp B', which can be fixed on any part of the wrought-iron bar or column B, thus forming a universal joint. This bar or column can be placed in position either horizontally or vertically, as may be most convenient, but is generally placed across the level, against the sides of which it is secured by means of the clamp I., and adjusting screw Μ, and claws N and N'. If necessary, wooden wedges 0, O' are driven in between the claws and the wall to make it still firmer. The weight of the bar is about 120 lb.”

Air-compressing plant of greater size has now been erected at Dolcoath mine, to which the above description refers. At Snailbeach mine in Shropshire they have two air-compressors of 18 inches diameter and 5 feet stroke; the air-main is at first 9 inches in diameter, then 6 inches, whilst 2-inch gas-pipe is used in the levels.

A rock-drill which has done, and is doing, excellent work is that of Mr John Darlington. Its construction will be understood by referring to figs. 29, 30, and 31; a is the cylinder, b the piston rod, c the borer; d, d are two openings for bringing in compressed air, either of which may be used according to the position of the drill; e is the inlet hose with a stopcock, /drill-holder, g stretcher bar, h piston, j rifled bar for turning piston and drill, k ratchet wheel attached to rifled bar, I rifled nut fixed in the piston head, m wood for lessening weight of piston rod and blocking space, n portway for allowing the compressed air to pass to the top of the piston and give the blow, o exhaust portway. The action oi the drill is as follows. The compressed air is always acting on the underside of the piston, and when the upper side of the piston communicates with the outer atmosphere the piston moves rapidly backwards and uncovers the portway n. The compressed air rushes through and presses against the upper side of the piston, which has a greater area than the lower side, the difference being equal to the area of the piston rod. The piston is driven rapidly downwards and the drill strikes its blow. At the same time it uncovers the exhaust port o and then the constant pressure on the annular area on the underside of the piston produces the return stroke. The number of blows per minute is from six hundred to eight hundred. The rotation of the drill is effected by the rifled bar. On the down-stroke of the piston the bar with its ratchet wheel is free to turn under a couple of pawls, and consequently the piston moves straight whilst the bar and ratchet wheel turn. When the up-stroke is being made the ratchet wheel is held by the pawls and the piston is forced to make part of a revolution. As the hole is deepened the cylinder is advanced forwards by turning the handle p ; this works an endleg screw q passing through a nut attached to the cylinder; r is the cradle carrying the feed-screw and supporting the cylinder. It is centred on the clamp s. As this clamp can be fixed in any position on the bar, and as the cradle can be turned on the clamp, it is evident that holes can be bored in any direction.

In driving a level with the Darlington drill it is usual to fix the stretcher bar horizontally across the level so as to command the upper part of the face; holes can then be bored with the cradle above the bar or below it. The bar is then shifted low enough to bore the bottom holes. It is found that all the necessary holes can be bored from two positions of the bar. The bar therefore has simply to be fixed twice; the alterations in position for boring holes in various directions are managed by shifting the clamp on the bar and turning the cradle on the clamp. Fig. 31 shows the stretcher bar fixed in a vertical position, which is sometimes convenient.

In order to clear out the sludge from holes that are “looking downwards,” a jet of water, supplied from a hose attached to a halfinch gas-pine leading from a cistern at a higher level, is made to play into the holes during the process of boring.

For sinking shafts Mr Darlington has the drill fixed in a cylindrical case with a large external thread which works in a nut on the clamp. The drill is fed forwards by turning a hand-wheel attached to the case.

Rotating machine drills are also used in mines as well as those with percussive action. Stapff pointed out some years ago that, if a rock may be chipped off by power communicated by a blow, it may also be chipped off by a similar amount of power communicated by pressure. Brandt’s rotatory boring-machine consists of a hollow borer which has a steel crown with cutting edges screwed on. The tool is kept tight against the rock by the pressure of a column of water, and is at the same time made to rotate by two little water-pressure engines, whilst a stream of water passing down through the borer washes away the débris and keeps the cutting edges cool. In principle, therefore, this drill resembles the original diamond boring machine of De la Roche-Tolay and Perret, save that the crown is made of steel and not of diamonds. During the last few years it has been tried with success in railway tunnels and in mines. Jarolimek’s drill acts also by rotation, but the borer is fed forwards and pressed against the rock by a differential screw arrangement. The machine can be worked by hand, or by a little water-pressure or compressed-air engine or an electro-motor. In working certain minerals occurring in seams the undercutting may be performed by machines similar to those used in coal mines (see vol. vi. p. 68).

We now come to the application of the tools and machine drills to the purpose of breaking ground for driving levels and sinking shafts.

A level or drift is a more or less horizontal passage or tunnel, whilst a shaft is a pit either vertical or inclined. In driving a level by hand labour in hard ground, the first thing the miner has to do is to take out a cut, i.e., blast out a preliminary opening in tħe “end” or “forebreast.” The position of this cut is determined by the joints, which the miner studies carefully so as to obtain the greatest advantage from these natural planes of division. Thus fig. 32 shows a case in which, owing to joints, it was advisable to begin with a hole No. 1, and then bore and blast 2, 3, and 4 one after the other. The miner as a rule does not plan the position of any hole until the previous one has done its work; in fact he regulates the position and depth of each hole by the particular circumstances of the case. Though a vein and its walls may be hard, there is occasionally a soft layer of clay (DD, DD, fig. 33) along one wall (<¾r, Cornwall; gouge, United States). The miner then works this away with the pick, and, having excavated a groove as deep as possible, he can now blast down the lode by side holes and so push the level forward.

In sinking a shaft a similar method of proceeding is observed. A little pit (s⅛λ) is blasted out in the most convenient part, and the excavation is widened to the full size by a succession of blasts, each hole being planned according to circumstances. This series of operations is repeated, and the shaft is thus gradually deepened.

Where boring machinery is employed, less attention, and sometimes no attention, is paid to natural joints, because when once the drill is in its place it is very little trouble to bore a few more holes, and the work can then be carried on according to a system which is certain of effecting the desired result.

A common method of procedure for hard ground is shown in figs. 34 and 35. Four centre holes are bored about a foot apart at first, but converging till at a depth of 3 feet they are within 6 inches, or less, of each other. Other holes are then bored around them until the end is pierced by twenty or thirty holes in all. The four centre holes are then charged and fired simultaneously, either by electricity or by Bickford’s instantaneous fuse, and the result is the removal of a large core of rock. The holes round the opening are then charged and fired, generally in volleys of several holes at a time, and the level is thus carried forward for a distance of 3 feet. If the ground is more favourable fewer holes are required, and they may be bored deeper,—in fact as much as 6 feet in some instances. Occasionally the four centre holes are directed so that they meet at the apex of an acute pyramid, and then, after all have been charged with blasting gelatin, only one of them receives a primer and cap; the shock of the explosion of one charge fires the other three adjacent charges simultaneously. The preliminary opening is not necessarily made in the centre of a level, and sometimes it is blasted out in the bottom or one side.

In sinking shafts by boring machinery operations are conducted much in the same way as in levels, save ot course that the holes are directed downwards. Fiers. 36 and 37 are a section and plan of a shaft which is now being sunk at the Foxdale mines in the Isle of Man.

About forty-five holes are bored in the bottom of the shaft before the drills are removed; two of the holes A, B, and occasionally four, are bored only 4 feet deep, and are blasted with ordinary fuse. They serve simply to smash up and weaken the core; then the six holes nearest the centre, which are 8 feet deep, are blasted all together with Bickford’s instantaneous fuse, and the result is the removal of a large core leaving a deep sink. The remaining holes are fired in volleys of four at a time in the ordinary way. In this manner the shaft, which is in hard granite, is being deepened at the rate of 3⅜ or 4 fathoms a month. Tonite is the explosive used.

Sundry machines have been invented and used for driving levels without blasting. Some cut up the face into small chips which can easily be removed, but they have not made their way at present into ordinary mining. The Bosscyeuse of MM. Dubois and François acts on a different principle. It is a strong machine worked by compressed air. It first of all drills holes 4 inches in diameter by percussion; a striking head is then substituted for the drill, and wedges, on the principle of the plug and feathers, are inserted into the holes; and powerful blows with the striking head wedge off the rock in lumps. This machine is being used with success in Belgium for driving levels and crosscuts in fiery mines.

Some comparative experiments between hand-labour, a percussive drill, and a rotatory drill have lately been made in one of the Freiberg mines, and the results are of much interest and importance. The actual figures are as follows, the cost including, in the case of the machines, interest, depreciation, and cost of repairs, and cost of steam-power, supposing water-power not available :— [table]

The advantages of machine work are very marked indeed both as regards rate and cost of driving, and wages earned by the men. Brandt’s rotatory drill did its work cheaper and faster than Schram’s machine; but nothing is said in the original notice of the advantage of a machine driven by compressed air for ventilating workings such as advanced headings in which these drills are employed.

Brandt’s machine was worked with water at a pressure of 83⅛ atmospheres, of which 56 ’ 6 atmospheres were obtained by pressure pumps provided with an accumulator, and 26’9 atmospheres by natural fall, owing to the working level being 277 metres below the pumps. The water was conveyed to the machine in iron pipes of 1⅛ inches diameter inside. The diameter of the holes bored was 2⅜ inches, and they could be bored in gneiss at the rate of 1⅜ inches per minute. The stretcher bar on which the machine is carried is hollow, and has a piston which can be forced out by hydraulic pressure so as to fix the bar firmly. A similar bar is sometimes used with percussive drills.

As a method of breaking ground the ancient process of fire-setting requires to be mentioned. Before blasting was known it was largely employed, but its use is now confined to a few places on the Continent where the rocks are exceedingly hard and where wood is abundant and cheap. Piles of wood are heaped up against the face of the workings and set on fire. On returning to the working place two or three days afterwards, when the rocks have cooled a little, it is found that the ground has split and flaked off, and that much has been loosened which can be removed by the pick and wedge.

We finally come to water as an agent for removing rocks. Streams of water were formerly used in South Wales for working beds of clay ironstone at the outcrop. The water washed away the clay and shale and left the clean nodules of ironstone. The china clay of Cornwall is also worked by water: a stream of water is turned on to the soft mass, and the workman loosens the ground with a pick; the water carries off the particles of decomposed rock in suspension to regular settling pits. Water under pressure has rendered vast services to the miner in working auriferous alluvia. The system is described and figured at p. 746 of vol. x., so it is unnecessary here to enter into details. In the special case of salt-mines recourse may be had to the solvent action of water, directed by suitable jets, for making excavations.

5. Principles of Employment of Mining Labour.— As a large proportion of the expenditure in mining is for actual manual labour, it is very important that means should be taken to prevent any waste in this department. Three principles are in vogue—payment by time, by work done either measured or weighéd, and by the value of the ore extracted.

The overseers, called captains in many metal mines, are naturally paid by the month, and where strict supervision can be exercised, such as is possible at the surface, on the dressing-floors for instance, the same principle may be adopted; but when men are working underground, and often in small gangs of only two or three persons at some distance apart, piecework of some kind is more economical and satisfactory in ev^ry way.

In driving levels and sinking shafts it is usual for the men to work at a certain price per running yard or fathom. The agents have to see that the excavation, whether shaft or level, is maintained of the full dimensions agreed upon, and preserved in the proper direction. At the end of a certain time, generally a month, the work is measured by the agent. From the gross amount obtained by multiplying the price by the number of fathoms driven or sunk it is necessary to deduct the cost of the materials supplied to the men by the mining company, such as explosives, steel, candles, Ac., and the remainder is divided among the persons who took the contract. When the useful mineral is being obtained the men may be paid at so much per cubic yard or fathom excavated, or at so much per ton of mineral extracted; the overseer of course has to see, in this latter case, that worthless rock is not sent to the surface. Payment by the number of inches bored is a method in use in some countries, where the men are not experienced or enterprising enough to undertake the work in any other way. A foreman points out to the men the position and direction in which the holes must be bored, measures them when completed, and subsequently charges and fires them.

The third method is that which is known as the tribute system. The miner working on tribute is allowed to speculate upon the value of the ore in a certain working area assigned to him and called his pitch. He gives the mining company all the ore he extracts at a certain proportion of its value, after he has paid all the cost of breaking it, hoisting it to the surface, and dressing it. Thus, supposing he takes a pitch at 5s. in the £, and produces marketable copper ore of the value of £50, his share will be 50 × 5s. =£12, 10s., less the cost of the materials he has been supplied with, and all expenses for winding, dressing, sampling, &c.

6. Means of Securing Excavations by Timber, Iron, and Masonry.— The following kinds of timber are those most frequently employed for securing excavations underground: oak, larch, pitch pine, spruce fir, and acacia. In ifiany mines the timber is attacked by dry rot, which gradually renders it useless, and when the timber has often to be renewed the expense may be very considerable. Various methods of preventing dry rot have been tried with more or less success, such as letting water trickle over the timber in the mine or treating it with preservative solutions beforehand. Brine, creosote, and solutions of chloride of zinc, sulphate of zinc, sulphate of copper, and sulphate of iron increase the duration of timber. It was found by experiments carried on at Commentry during a long series of years that one of the best plans‘was to soak the timber for twenty-four hours in a strong solution of sulphate of iron. The total cost was only jd. per yard of prop, whilst the timber lasted eleven times as long as when this simple treatment was omitted.

Timber is used in various forms—either whole and merely sawn into lengths, or squared up, or sawn in half, or sawn into planks of various thicknesses.

Where the roof of a bed is weak it may be kept up by simple props; but in some coalmines and clay-mines a better support is obtained by logs (chocks) laid two by two crosswise (fig. 38).

Though a level is an excavation of a very simple nature, the methods of timbering it vary considerably, because the parts requiring support may either be the roof alone, or the roof and one or two sides, or the roof, sides, and bottom.

If the roof only is weak, as is the case with a soft lode between two hard walls, a cap with a few boards resting on ⅛ (fig. 39) is sufficient to prevent falls. If one side is weak the cap must be supported by a side prop or leg (fig. 40), and very often by two legs. The forms of joint between the cap and leg are numerous

(fig. 41), depending to a great extent upon the nature of the pressure, whether coming upon the top or sides. With round timber the top of the leg is sometimes hollowed as shown in fig. 42 A, but occasionally the joint is flat and a thick nail, or nog, is put in (fig. 42 B)

to prevent the effects of side pressure, or, better, a piece of thick plank is nailed under the cap (fig. 43). Where the floor of a level is soft and weak, a sole-piece or sill becomes necessary, and, if the sides or roof are likely to fall in, a lining of poles or planks is used (fig. 43).

In some very heavy ground in the Comstock lode a special system of timbering is adopted (fig. 44).

If the ground is loose, so that the roof or sides, or both, will run in unless immediately supported, the method of working called spilling or poling is pursued. It consists in supporting the weak parts by boards or poles kept in advance of the last frame set up. The poles or boards (laths) are driven forward by blows from a sledge, and the ground is then worked away with the pick; as soon as a sufficient advance has been made a new frame is set up to support the ends of the poles or boards and the process is repeated (figs. 46 and

46). In running ground it is necessary to have the laths fitting closely together, and the working face also must be supported by breast-boards kept in place by little struts resting against the frame. These are removed and advanced one by one after the laths in the roof and side have been driven beyond them.

On account of the high price of timber, iron is sometimes employed in its place. One method in use in the Harz consists in bending a rail into the form shown in fig. 47 and making it support other rails laid longitudinally, against which flattish stones are placed; the vacant spaces are then filled with rubbish.

Masonry has long been used for supporting the sides of mining excavations. The materials necessary are stone, ordinary bricks, or slag-bricks, and they may be built up alone (dry walling) or with the aid of mortar or hydraulic cement. The bottom of a level is occasionally lined with concrete to carry a large stream of water, which otherwise might run into lower workings through cracks and crevices. Dry walling is not uncommon, and it may be combined with the use of timber (or iron) as shown in fig. 69, in which a level is maintained between two walls keeping back a mass of rubbish.

Figs. 48 and 49 show methods of securing a drift by arches when a lode has been removed.

The timbering required for shafts varies according to the nature of the ground and the size of the excavation. A mere lining of planks set on their edges (fig. 50) suffices for small shafts, corner pieces being nailed to keep the successive frames together. In some of the salt-mines of Cheshire the shafts are lined with 4-inch planks united by mortice and tenon joints.

The usual method of securing shafts is by sets or frames. Each set consists of four pieces, two longer ones called wall-plates and two shorter ones called endpieces. They are joined by simply halving the timber as shown in fig. 51. A more complicated joint (fig. 52) is often preferred. The separate frames are kept apart by corner pieces (studdies, Cornwall; jogs, Flintshire), and loose ground is prevented from falling in by boards or poles outside the frames.

As shafts are frequently used for the several purposes of pumping, hoisting, and affording means of ingress and egress by ladders, it becomes necessary in such cases to divide them into compartments. Pieces of timber parallel to the end-pieces (buntons or dividings) are fixed across the shaft, and serve to stay the wall-plates and carry the guides as well as to support planks (casing boards) which are nailed to them so as to form a continuous partition or brattice. The magnificent timbering of some of the shafts on the Comstock lode is described by Mr James D. Hague as follows: — “The timbering consists of framed sets or cribs of square timber, placed horizontally, 4 feet apart, and separated by uprights or posts introduced between them. Cross-timbers for the partitions between the compartments form a part of every set. The whole is covered on the outside by a lagging of 3-inch plank placed vertically.” Figs. 53, 54, and 55, copied from Mr Hague’s plates, illustrate this method of timbering. Fig. 53 is a plan of the shaft: “S, S are the longitudinal or all-timbers, T, T the transverse end-timbers, P partitiontimbers, τ guide-rods between λvhich the cage moves, g gains cut in the sill-timbers, to receive the ends of the posts. The sheathing or lagging is seen enclosing the whole frame?’ Fig. 54 is a transverse section through the partition P of fig. 53, “between the pumping compartment and the adjoining hoisting compartment, looking towards the latter. In this figure, G, G are the posts, S the sill-timbers, P the partition-timbers, the ends of which are framed with short tenons that are received in gains cut in the silltimbers and the ends of the posts, r guide-rod, I lagging or sheathing.” Fig. 55 is an end view of the frame shown in fig. 53. “The single piece T forms the end, while the double pieces P forming the partitions are seen beyond.” “The outer timbers of each set, that is, the two sides and ends of the main frame, are 14 inches square; the posts, ten in number, four at the comers and two at each end of the three partitions, are of the same size. The dividing timbers, forming the partitions, are 12 inches square.”

When ground is loose or running, recourse must be had to a spilling process like that described for levels. Strong balks of timber are fixed at the surface or in solid ground, and then the first frame is hung from these bearers, and each successive frame from the one above it. Iron bars with cotters may be used for suspending the sets; but on the Comstock lode each bolt is made in two parts with a tightening screw in the middle, and the sets can thus be kept very firmly together. The laths are driven in advance, in the manner explained in the case of levels, and a new frame is put in as soon as the excavation has been sufficiently deepened within the protecting sheath of boards. In very unstable ground it may be necessary to put in the frames touching each other, so that the shaft becomes encased in a solid box of timber, occasionally 14 inches thick.

Like levels, shafts may be lined with masonry or brickwork, and these have the advantage of being far more permanent than timber, and of requiring fewer repairs. This kind of shaft-lining is especially desirable in the loose ground near the surface; because, if the working is discontinued temporarily, the shaft still remains secure and available for use at any future time, whereas if timber is put in it often decays, the top of the shaft collapses, and much expense is incurred in the process of reopening it. The section of the shafts that are walled is generally circular as affording the best resistance to pressure; but elliptical walling is also met with. Another shape is like a rectangle, save that the sides, instead of being straight, form curves of large radius. The walling may be dry or with mortar, according to circumstances.

The masonry is put in either in one length or in successive portions in descending order, and this is the usual plan. The shaft is sunk a certain depth, with temporary timbering if necessary, and when firm ground has been reached a bed is cut out round the shaft, and on this is placed a crib or curb AB (fig. 56) consisting of segments of timber which form a ring. This serves for a foundation for the brickwork, which is built up to the surface; the temporary timbering is removed, and the space filled up with earth or concrete. Sinking is then resumed below the curb, and for a certain distance of a smaller diameter, so as to leave a bracket, or ledge, to support the first curb. On arriving, after a certain depth of sinking, at another firm bed, a second curb CD is put in and a portion of brickwork built up. When the ledge of rock is reached, it is carefully removed in small sections and the brickwork brought up to the first curb. This process is repeated till the shaft is completed, or reaches rock in which no masonry is requisite. If, owing to the nature of the ground, it is impossible at first to find a firm seat for the curbs, it becomes necessary to hang them by iron bolts from a strong bearing frame at the surface.

When shafts pass through very watery strata, it is most desirable to stop all influx into the mine for the purpose of saving the heavy expense of pumping. The manner in which this is effected by a watertight lining, known as tubbing, is described in the article Coal, vol. vi. p. 62, where will also be found an account of Triger’s plan of sinking shafts with compressed air, and the very successful method of boring shafts through water-bearing ground invented by Messrs Kind & Chaudron,

7. Exploitation, or Working Away of Veins, Beds, and Masses.— We have described how shafts are sunk and levels driven, and we now come to the processes employed in removing the mineral.

The deposit must first of all be reached by a shaft, or, where the contour of the country permits it, by a level. In the case of a vein an exploratory shaft is often sunk on the course of the lode for 20 or 30 fathoms, and, if the indications found in a level driven out from this shaft warrant further prosecution of the mine, a first working shaft is sunk to intersect the lode at a depth of 100 fathoms or more from the surface. Crosscuts are then driven out at intervals of 10,15, or 20 fathoms to reach the lode, as shown in fig. 57, which represents a section at right angles to the line of strike. Sometimes the main shafts are carried down all the way along the dip of the deposit, though perpendicular shafts have the advantages of quicker and cheaper winding and cheaper pumping, to say nothing of the possibility of utilizing the cages for the rapid descent and ascent of the miners. If an inclined shaft appears to be advisable, great care should be taken to sink it in a straight line. In either case levels are driven out along the strike of the lode as shown in the longitudinal section fig. 58, in the hopes of meeting with valuable ore-

bodies such as are represented by the stippled portions of the figure. For the purpose of affording ventilation, and still further exploring the ground and working it, intermediate shafts, called winzes (Cornwall) or sumps (North Wales), are sunk in the lode.

The actual mode of removing the lode itself depends a good deal upon circumstances, viz., its width, the nature of its contents, and the walls that enclose it; but the methods of working may generally be brought under one of two heads, viz., underhand stoping or overhand stoping. The word slope is equivalent to step, and the term stoping means working away any deposit in a series of steps. Underhand or bottom stopes are workings arranged like the steps of a staircase seen from above, whilst overhand or back stopes are like similar steps seen from underneath. Both methods have their advantages and disadvantages, and both are largely used.

We will first take underhand stoping, as this is the older method. In the old days the miner began in the floor of the level (fig. 59), and sank down a few feet, removing the part 1; he followed with 2, 3, 4, &c., until the excavation finally presented the appearanc∙ shown in fig. 60. Any valueless rock or mineral was deposited upon platforms of timber (stulls), and the ore was drawn up into the level by a windlass. One great disadvantage of this method is that the ore and water have to be drawn up some distance by hand labour; much timber is required for the stulls if there is a large quantity of worthless stuff in the vein, or if the sides are weak. The advantages are that ore can be worked away as soon as the level is driven, that the men are always boring downwards, and, lastly, that the ore can be carefully picked after it is broken, without fear of any valuable particles being lost.

A more economical method of working by underhand stopes, and one largely employed in Cornwall at the present day, consists in reserving any attack upon the ore-ground until a lower level has been driven. An intermediate shaft {winze) between the two levels is then made, either by sinking from the upper level or rising from the lower one. The work of stoping is commenced at the two upper ends of the winze, and the lode is removed in a succession of steps, the workings assuming the appearance exhibited in fig. 61. The steps are generally made steep, so that the ore may readily roll into the winze, and so that the bore-holes may do better execution; but these steep stopes are dangerous if a man happens to slip and fall. The huge open chasms left by the removal of a large lode in this way are also a source of danger; for there is always a risk of falls of rock, and from places which cannot easily be examined.

Figs. 62 and 63, kindly supplied by Captain Josiah Thomas, explain the general arrangement of the workings of the largest tin mine in Cornwall. The lode after producing copper ores to a considerable depth changed its character and became rich in tin. The workings for tin ore are confined almost entirely, to the granite. The section fig. 62 shows that the mam shaft of the mine is at first vertical and then carried down on the dip of the lode.

The process of overhand stoping is precisely the reverse of that which has been just described; the work is commenced from a rise

(fig. 64 A), or better from the two bottom ends of a winze (fig. 64 B). As soon as the men have excavated a sufficient height of the roof of the level, they put in strong pieces of timber from wall to wall, and cover these cross-pieces {Stempels, stull-pieces') with boards or poles, and throw down the rubbish upon the platform (stull, bunning) thus formed. In the midst of the rubbish chimney· like openings (mills, passes) are reserved, lined with boards or dry-walling, and closed at the bottom with shoots provided with doors. The ore is thrown into these passes, which are tapped when necessary; the ore falls into the tram-waggon placed ready to receive it.

Fig. 65 gives a transverse section showing the rubbish resting on the stull. This is what may be called the typical method of stoping, when the lode affords rubbish enough for the men to stand on and to keep them close to the rock they are attacking. Very often such is not the case, and the whole of the lode has to be sent to the surface for treatment. If the walls are firm, the lode is sometimes stoped away, a stull put in, and a sufficient heap of broken ore is left upon the stull to give the men good standing ground; the excess is thrown over the ends of the stu∏, or the great heap is tapped by cutting a hole in the stull-covering, and allowing a quantity to run down into the level.

Another method consists in putting in temporary stages upon which the men stand to do their work, whilst the excavation is left as an open space (fig. 66). This mode of working is incompatible with weak walls. If a lode does not afford rubbish enough for completely filling up the excavated space, or if it is too narrow for men to do their work comfortably, one of the walls may be cut into and blasted down (fig. 67), so that the men always stand upon a firm bed of rubbish while at work, and there is no fear of a collapse of the mine. In certain special cases rubbish is sent down from the surface to fill up the excavations.

The advantages of overhand stoping are — that the miner is assisted by gravity in his work, that no ore or rock has to be drawn up by hand labour, and that less timber is required. On the other hand, the miner is always menaced by falls, but as he is close by he can constantly test the solidity of the roof and sides by sounding them with his sledge; there is the further disadvantage that particles of ore may be lost in the rubbish, but this loss is often prevented by laying down boards or sheets of iron while the lode is being broken down.

When very wide lodes come to be worked, recourse is often had to special methods. The great lode at the famous Van mine, in Montgomeryshire, is sometimes 40 feet in width, and the hanging wall is weak. The lode is stoped away overhand, and the cavities packed with rubbish, part of which is derived from the lode itself, whilst the greater portion is supplied from a special quarry at the surface. Fig. 68 explains the details of the case. A is the original cross cut (not in the line of section) by which the lode was reached, B is the flucan, C the bastard lode, generally worthless, E the main lode, H permanent levels, and K ore-pass reserved amidst the rubbish (deads) D, I pass down which rubbish is shot, N crosscut connecting the level H with P the permanent level in the country.

If the lode is not firm enough to allow of the stopes being carried for its full width, the crosscut method is adopted; the workings in this case, instead of proceeding along the strike, are carried across the deposit from one wall to another.

The lode is removed in successive horizontal slices A,B,C,D,E, and for each slice a level (I., fig. 69) is driven, either in the lode.

or partly or entirely in the country; from this level crosscuts arc put out 6 or 8 feet wide, as shown in the plan (fig. 70). These arc regularly timbered according to the necessities of the case, and, when No. 1 is completed, No. 2 is begun, and the rubbish from No. 2 thrown into the empty space of No. 1 crosscut. If the quantity is insufficient, deads are brought in from the surface oι from exploratory workings in worthless rock in the neighbourhood. Sometimes the crosscuts are not driven side by side, but 1 and 5 would be driven first, leaving 2, 3, and 4 as a solid pillar; then 3 would be worked away, and finally 2 and 4 between the timber and rubbish on each side. The greater part of the timber can be recovered when the next slice above is taken off, as the props are put in with the small ends downwards, and can be drawn up with levers. Μ (fig. 69) is a level reserved in the deads for traffic and ventilation. This method of working is applicable not only to lodes but also to irregular masses.

In working away the soft “bonanzas” or ore-bodies of the great Comstock lode, which are from 10 to 30 or even 40 or 50 feet wide, and which are enclosed in very unstable ground, a special method of timbering is employed (figs. 71 and 72). “It consists in framing timbers together in rectangular sets, each set being composed of a square base placed horizontally, formed of four timbers, sills, and cross-pieces, 4 to 6 feet long, framed together, surmounted by four posts 6 to 7 feet high, at each comer, and capped by a frame-work, similar to that of the base. These cap-pieces, forming the top of any set, are at the same time the sills or base of the next set above, the posts, as the sets rise one above the other in the stope, being generally placed in position directly over those below.” “The timbers are usually of 12-inch stuff square-hewn or sawn.” Each post has a tenon 9 inches long at the upper end, and a tenon of 2 inches at the lower end, which fit into mortices in the cap and sill respectively; and “the sills and caps have short tenons on each end and shoulders cut to receive the ends of the post and the horizontal cross-pieces.” The walls of the excavation are sustained by a lagging of 3-inch or 4-inch plank. The whole width of the ore-body is stoped away at once, and its place ≡lied by timbering, and ly the vacant space is filled with waste rock derived from dead work in the mine or from special excavations, — underground quarries in fact,—in barren ground. The stoping is carried on overhand, starting from an intermediate shaft or winze, and fig. 73 will explain how the different frames are built up one above the other.

Another method of working a wide lode is to attack it in slices parallel to the dip, working away each slice separately as if it were a lode of ordinary dimensions, and filling up with rubbish (fig. 74).

We now come to beds or seams. The mode of working the most important beds that occur in the earth’s crust, viz., coal seams, has already been described in the article Coal (vol. vi. p. 64 sq.), and details have been given concerning the removal of the mineral by pillai’ working and long-wall working. Both these methods are applicable in the case of seams of other minerals. Such for instance are the beds of fire-clay and clay-ironstone which are -wrought by both the processes just mentioned, and often in connexion with coal.

Next in importance to coal is ironstone, and a brief account of the workings in the Cleveland district will explain the manner in which more than one-third of the iron ore raised in the British Isles is obtained by mining. It resembles the ‘ ‘ bord and pillar” system used for working coal in Durham.

The Cleveland ore occurs in the form of a bed from 6 to 16 feet thick in the Middle Lias, lying pretty level. A mainway (fig. 75) is driven about 12 feet wide for a considerable distance, and at right angles to it bords are driven 5 yards wide for a length of 30 yards, and then at right angles a wall 7 or 8 feet wide and 20 yards long. By drivages of this kind the bed is cut up into pillars or blocks 30 yards long by 20 yards wide. The pillars are subsequently removed in the following way. A place, or drift, ab, 6 feet wide, is driven across the pillar 10 yards from the corner, and portions (lifts) about 6 yards wide are worked away in the order 1, 2, 3. After No. 1 lift has been removed, the timber put in to support the roof temporarily is withdrawn, and the roof is allowed to fall; No. 2 is then taken, and No. 3 in the same way. While these lifts are being taken out, another place cd is being driven across the pillar 10 yards from the first, and the pillar removed entirely by a series of fresh lifts.

Fig. 76 represents in section and plan the chambers and pillars of the underground gypsum quarries which supply the well-known plaster of Paris to all the world. The principal bed is from 50 to 60 feet in thickness; pillars are left 10 feet square at the base, and the stalls between them are 16 feet wide. The workings are slightly arched, and are not carried up to the roof, for the purpose of better maintaining the security of the chambers, because heavy damages would have to be paid if they “caved in” and rendered the surface useless. A similar layer left for the floor prevents creep (see Coal, vol. vi. p. 64), and enables the underground roads to be kept in good repair.

Underground slate quarries afford examples of very various methods of removing thick beds of mineral of comparatively little intrinsic value. At Angers in France, where the beds dip at a high angle, the underground workings are carried on like an open quarry under a trong roof of slate; the floor is continually being worked away in steps, and an immense open chamber is left. In the

Festiniog district in North Wales the principal bed, or vein as it is called, is more than 100 feet thick in places, and the method of working consists in making alternate pillars and chambers each 30 feet to 50 feet wide along the strike (cross-section and plan, figs. 77 and 78). The pillars follow lines of natural cross-rending PP ’, which commonly make an angle of 25° to 35° with the direction of the dip. The excavations are arranged in regular lines, and form continuous chambers extending very often from the surface to the very lowest workings. A, B,C,D are the original working levels. The slate of the supporting pillars is entirely lost, as these cannot be removed with safety. This method of working requires a strong roof. In the Ardennes, on the contrary, the pillars are carried along indefinitely along the strike (fig. 79, cross-section). The slate in each longitudinal chamber is removed in slices parallel to the bedding, and the men stand upon the rubbish, which finally fills up the chambers completely.

Rock-salt constitutes another important mineral which occurs in the form of stratified deposits. The principal source of the Cheshire salt is a bed 84 feet thick lying horizontally; but only the bottom part, 15 feet to 18 feet thick, is mined. Pillars 10 yards square are left promiscuously about 25 yards apart, as shown in fig. 80, which represents part of Marston Hall rock-salt mine. The workings are advanced by making in the upper part an excavation 5 feet 9 inches high, called the roofing (a, fig. 81); and then the lower two-thirds of the part worked are removed by blasting slanting holes. Many of the old salt mines have collapsed from weakness of the roof or insufficiency of the pillars, and have become inundated; the brine is then extracted by pumping and evaporated for salt.

In some countries, especially when the beds of salt are impure or much mixed with clay or shale, the formation of brine is conducted regularly by making a network of drivages within a rectangular, elliptical, or circular area in thick beds of saliferous marl, and then introducing fresh water by pipes, so as to form underground ponds which gradually dissolve the roof and sides. The brine is drawn off and either pumped up or conveyed by adits to the surface.

A few words remain to be said about open workings. Some minerals are always obtained in this way; others are worked open before regular underground mining begins; and, thirdly, it often happens that underground and surface work are both carried on simultaneously on the same deposit. Among deposits worked opencast are peat, numerous kinds of stone, iron ore, cupreous pyrites, lead ore, gold-and tin-bearing alluvia, and diamantiferous rock.

Owing to its soft, spongy, and fibrous texture, and the fact of its often lying below the water-level, peat has to be worked in a special manner. Trenches are dug about a foot deep with a sharp spade, which cuts out sods of convenient size for drying and burning. When one layer has been removed in this way, another is taken off, and so on. If water is reached the working can still be pursued by using the long spade (grand louclιet, France) with a handle of 16 or 20 feet. It cuts out a sod 3 or 4 feet long at each thrust.

When a deposit is more or less solid the workings are frequently arranged in steps, the height and breadth of each depending upon the firmness of the rock.

In many cases the first work consists in removing worthless rock at the surface (overbτιrden), and where the underlying deposit is thick or very valuable it will pay to remove a very great thickness of overburden, on account of tne advantages of working a deposit open. These advantages are—entire removal of the deposit without loss in pillars, no expense for timbering or for packing with rubbish or for ventilating or lighting the workings, better ventilation, easier supervision, longer working hours, less danger.

As an example of a large open working may be mentioned the great Penrhyn slate quarry near Bangor, employing about 3000 hands, and worked by a succession of terraces on an average 60 feet high by 30 feet wide (fig. 82). Reference has already been made to the thick lead-bearing sandstone of Mechernich, which is in part worked as an open quarry. Mokta-el-Hadid, near Bona in Algeria, and the Rio Tinto mines in Spain, afford instances of extensive combined open and underground workings for iron ore and cupriferous pyrites respectively.

Local laws regulating the size of the working areas, or claims, owned by separate individuals or companies, considerably affect the methods of working. This is especially the case with the diamond deposits of South Africa. The diamantiferous rock at the celebrated Kimberley mine (formerly called Colesberg Kopje) occurs in the shape of an elliptical upright mass, the greatest length being about 330 yards and the greatest breadth about 200 yards. The superficial area is about 9 acres; the mass extends downwards within almost perpendicular walls of shale, and is worked in places to a depth of about 400 feet. The claims are only 31 feet square, and are more than four hundred in number, and these have in some instances been subdivided into portions as small as the sixteenth of a claim; but, as at the present time one company may own very many claims, the number of individual holdings is less numerous than formerly when the limit was two claims. The working is earned on vertically downwards, and, as the claims are not all worked at the same rate, those that progress most rapidly are surrounded by perpendicular walls of neighbouring claims. The shale, or reef, enclosing the deposit is constantly falling into the huge open pit, and has to be cut away to a slope, the expense of this work being charged to the claim-holders generally by the mining board. The diamantiferous rock is extracted by innumerable wire-rope inclines.

We have already referred to the method of working gold-bearing alluvia by the hydraulic process, which has rendered such services in the United States (Gold, vol. x. p. 746). At the same time one must not be blind to the evils of this method of working, which have at last necessitated legislative interference. Some idea of the extent of the mischievous results of hydraulic mining will be gathered from the statement that one working alone, the Gold Run Ditch and Mining Company, for the last eight years has been discharging 4000 to 5000 cubic yards of sand, gravel, and boulders daily, for a period of five months each year, into a tributary of the Sacramento. As a natural consequence deposits are formed lower down the river, obstructing the navigable channels, rendering overflows more frequent and destructive, and causing valuable land to be destroyed by deposits of sand. The superior court of Sacramento county, California, has recently decided that the hydraulic mining companies must build dams to impound the coarse and heavy debris, or take other efficacious means to prevent their being washed down the rivers.

8. Carriage or Transport of Minerals along the Underground Roads.— After the mineral has been broken down in a deposit it is necessary to pick out any barren rock and then convey to the surface all that is of value.

The simplest and oldest method of transport along underground roads is carriage on the back, and this method may still be seen at the present day even in countries where the art of mining is generally highly advanced. Thus, for instance, in the little slate mines near Cochem on the Moselle men and lads carry up all the blocks of slate upon their backs, walking upon steps cut in the rock; they come up with their hands upon the ground bent almost double under the weight of the block, which rests upon a thick pad. Again, the blocks of slate are still carried on the back from the actual working place to the nearest tram-road, in the slate mines of the Ardennes. In the Sicilian sulphur mines the same method is common, and it is found also in parts of Spain and China, where baskets are used, whilst bags are employed in Mexico and also in Japan. Even in England the system still survives in the Forest of Dean, where boys carry iron ore in wooden trays from the very irregular ore-producing cavities either to the surface or to the nearest shaft.

Sledges, or sleds, enable greater loads to be transported; but they are not available unless the conveyance is along roads sloping downwards. They have been largely employed in coal mines, and are still resorted to in some collieries for conveying the coal from the working place to the nearest tram-road.

We next come to wheeled carriages. The simplest is the wheelbarrow. The barrow used in Cornwall at the present day is not unlike that figured more than three centuries ago by Agricola. The navvy’s barrow is more advantageous, but it requires a wider and higher level. The barrow runs upon the natural floor of the level, upon boards, or upon thin strips of iron. Carts drawn by horses may be used in large underground quarries. Excepting in special cases it is advisable to replace barrows by waggons running upon rails. * The oldest form is the German Hund.

It consists of a rectangular wooden body, with four wheels, resting upon two boards as rails, and it is kept on the track by a pin which runs between the boards.

Cast-iron tram-plates were introduced in the last century, and were finally succeeded by iron rails, which are now in general use, though steel threatens to displace iron in this as in other departments of mining. Various forms of rail are employed. The simplest is a bar of iron set on its edge in transverse sleepers, or flat iron nailed to longitudinal sleepers. Small T-headed and bridge rails are not uncommon. In the Harz the rails sometimes lie on stone sleepers; a hole is bored in the stone, plugged with wood, and the rail is nailed on. The gauge varies from 14 inches to 3 feet or more; 20 inches to 22 inches is a common gauge in metal mines. Arrangements of course have to be made for passing from one line to another by points ; but the transference is frequently best effected by putting down flat plates of cast iron, upon the smooth surface of which the waggons can be handled with ease and turned in any direction; raised ledges guide the wheels into any particular track.

The form and size of the waggons running upon the rails necessarily vary according to the size of the underground roads and the manner in which the mineral is raised in the shaft. In some mines the practice exists of loading the mineral in the level into an iron bucket (kibble) standing upon a trolley, which is merely a small platform upon wheels. This trolley is pushed (trammed) to the shaft; the full kibble is hooked on to the winding-rope and drawn up, whilst an empty kibble is placed upon the trolley and trammed back along the level, where it is again loaded from a shoot (mill, pass) or by the shovel. The usual plan, however, is to have a waggon, which is tipped on coming to an enlargement of the shaft (plat, lodge) where the level joins it. These waggons may be made of wood or sheet-iron, and of late years sheet-steel for the body and caststeel for the wheels have been coming into favour.

The most modern system in metal mines is to imitate collieries, and use waggons which are drawn up in cages. Fig. 83 represents the plain but strong waggon of the Van mines, consisting of a rectangular body of sheet-iron resting on an oak frame, and provided with cast-steel wheels. The wheels are loose upon the axles, which themselves run loose in the pedestals. The waggon is emptied by being run on to a “tippler,” which enables it to be completely overturned with great ease. A commoner plan is to construct the waggon with a hinged door at one end, and the contents are discharged by opening this door and raising the body.

The motive power for tramming waggons along the levels of metal mines is generally supplied by men or boys, though, where large quantities have to be extracted, and where the roads are favourable, recourse may be had to ponies and horses and the various kinds of mechanical haulage described in Coal, vol. vi. p. 69.

Trains of cars are sometimes drawn along underground railways by locomotives; they have the great disadvantage of polluting the air with the products of combustion, and consequently they are not available unless the ventilation is very good. A small locomotive of 2 horse-power nominal is used on an 18⅛-inch track in the adit-level of the Great Laxey mine (Isle of Man), now approaching a mile in length, and full-sized locomotives ply along the adit of the Rio Tinto mines. Locomotives worked by compressed air improve the ventilation instead of injuring it, and are not a source of danger in cases where fire-damp may be present; but, except in special cases, they cannot be worked so cheaply as engines fired with coal. Conveyance by electric railroads underground has hardly gone beyond the experimental stage, but the results obtained at the Zaukeroda colliery in Saxony show that electricity can be applied with profit in this department of mining.

A few instances of transport by boats may still be met with. The boats used in the underground canal at Klausthal are 31 feet long by 4 feet 6 inches wide, and 2 feet 11 inches deep. Each boat carries 5 or 6 tons.

Where roads have a strong gradient, inclined planes are employed, either self-acting if the mineral has to be lowered, or worked by stationary engines if the mineral has to be raised (see Coal, vol. vi. p. 69).

9. Winding, or Raising in the Shafts, with the Machinery and Apparatus required.— In speaking of the transport by underground roads, we mentioned that the mineral is occasionally brought to the surface on the backs of men or boys. In other cases daylight is reached by adit-levels provided with railroads; but in by far the greater number of mines it is necessary to hoist the mineral, and often much rubbish, up vertical or inclined pits generally known as shafts.

In beginning to sink a shaft from the surface, or in sinking a winze, hand-power applied by a windlass is sufficient. The broken rock at the bott<5m of the shaft is shovelled into a wooden or iron bucket (kibble), which is drawn up by a rope passing round the barrel of the windlass. When a depth of 20 or 30 yards has been reached it is more advantageous to introduce horse-power, and the usual machine by which this power is applied, called a gin or horse-whim, is a common sight in many metalliferous districts. It consists of a vertical axis carrying a barrel or drum 8 to 12 feet in diameter, round which is coiled the rope, which after passing over a pulley hangs down the shaft. The axis carries an iron pin at each end, the lower one working in a stone and the upper one in a socket in the span-beam or cross-bar of the supporting frame. Under the barrel is a long driving beam to which a horse is harnessed, and, as will be readily understood, the kibble is drawn up or lowered down as the horse walks round. It is most economical to have two kibbles, for then they balance each other.

Where steam and water-power are not available, a large number of horses or mules are sometimes harnessed to whims, and ore raised from depths of 200 fathoms. These, however, are exceptional cases; and, especially since the introduction of portable engines, the use of steam-power even for comparatively small depths, such as 100 yards, is daily increasing. In hilly districts water-power is generally at. hand, and huge reservoirs are frequently constructed for storing the rainfall, and so affording an adequate and constant supply. It may be utilized by water-wheels, turbines, and water-pressure engines.

There are three systems of winding by steam or waterpower which are in regular use :—(1) by buckets (kibbles), baskets, or bags swinging loose in the shafts; (2) by boxes working between guides (skips, Cornwall); (3) by cages carrying one or more waggons.

The buckets are made of wood, sheet-iron, or sheet-steel. Their shape varies; it may be round or elliptical, straight in the side or bulging in the middle. Fig. 84 represents a kibble made of sheet-iron. When the shaft is inclined, the side upon which the kibble slides is carefully lined with boards (bed-planks) resting upon cross sleepers. Planks of hard wood like beech last longer and require fewer repairs than deal boards. In the Harz, poles fixed lengthwise take the place of boards, which are customary in Great Britain. Even where shafts are perpendicular a lining of planks is often put in round the winding compartment, unless the space is considerable, and the kibble then glides up smoothly, and there is less risk of accidents. A more modern system is to use wire-rope guides for the kibble, which is thus kept from swinging about. Another advantage of this plan is that a light cage can easily be substituted for the kibble and used for the ascent and descent of the men. Mr Galloway has patented a method of sinking shafts with wire-rope guides, the upper ends of which are coiled upon drums at the surface. By adopting this expedient the guides can be lengthened as the shaft is deepened.

A word must be said about the actual loading and emptying of the kibble. Sometimes, as already mentioned, the kibble is filled at the working place or from a shoot (pass, Cornwall) carried down into the level, and then conveyed on a trolley to the shaft, where it is hooked on to the rope and drawn up. More frequently the filler standing in the plat loads the kibble with a shovel; and in order to save time two kibbles are often provided, one being filled while the other is making the journey to and from the surface. In this case it is necessary to have some kind of clevis, which will enable the kibble to be readily detached from the winding-rope, and quickly and securely fastened on again. On its arriving at the surface the lander seizes an eye or ring at the bottom of the kibble by a pair of tongs suspended by a chain, and the rope is now lowered. The kibble is thus turned over and the contents fall into a tram-waggon.

The inconveniences of this method of winding are considerable, especially in inclined shafts where the direction and amount of the inclination are not constant. There is great wear and tear of the bed-plank and casing-boards; and, unless constant attention is paid to repairs, places are worn out where the kibble catches, causing the rope to break. The fall of a kibble and its contents not only does much damage to the shaft, but also is a source of danger to the men. The introduction of boxes (skips) working between guides or conductors was therefore a decided step in advance, for the system allows the winding to be carried on with less friction and with greater rapidity and safety. The guides are often'made of pieces of timber (like r, fig. 53) bolted to the endpieces and dividings. It is only in perpendicular shafts that guides made of wire-rope or iron rods can be applied. The skip is a box of rectangular section made of sheet-iron or sheet-steel, with a sloping bottom, and provided with a hinged door closed by a bolt for discharging its contents. Fig. 85 shows how the skip runs upon the guides by means of four cast-iron or (better) cast-steel wheels. In an inclined shaft the guides sometimes have iron rails laid on them so as to diminish the wear. Some of the skips in Cornwall are made to hold as much as a ton and a half of tin-bearing rock. The skip is filled with a shovel by a man standing in the plat, but a better plan is to arrange shoots leading from large hoppers, so that the ore can be made to run in without any shovelling. The skip is sometimes tilted completely over instead of being emptied by a hinged door; this arrangement is in use in some of the German mines, where the skip is made of wood, and is guided on each side by two pins or rollers running between two conductors. When the skip has reached the surface two catches are made to support the lower rollers, whilst the upper ones pass through openings in the front guides, ahd the skip, turning upon the lower ones, is tipped over and so emptied.

The most satisfactory system of winding is by cages; there is less handling of the mineral, and the hoisting proceeds at far greater speed. This system, which is almost universal· in collieries, is employed also for working deposits of other minerals, and, though in vein-mining the skip and kibble still prevail in England, the managers are beginning to recognize the advantages of the cage and equip their mines with more modern appliances than have hitherto been customary. The cages used in the mines on the Comstock lode are very light and simple in construction, as will be seen from fig. 86. The cage in fact is a mere timber platform, 5 feet by 4, resting on iron bars p, and supported by iron rods on each side. It is provided with a sheet-iron bonnet to protect the men if they are inside, and also with safety catches t, t, which come into play if the rope breaks. The hand levers k, k at the ends of the cage raise up blocks which keep the car in its place during the ascent or descent: g, g are guides for the end of the crossbar b ; c, bar working teeth t, t by levers; f, “ear” or “shoe” embracing the guide-rod in shaft; r, lifting bar; s, strong spring.

The most important details concerning the use of cages, ropes, and other hoisting appliances such as pulleys, pulley-frames, detaching hooks, and winding engines, have already been set forth in the article Coal, vol. vi. p. 74; and it is therefore needless to repeat these particulars, especially as the art of winding mineral cheaply, speedily, and safely has been carried to a far greater pitch of perfection in collieries than in the majority of metal mines. It is often convenient to fix winding engines underground for the purpose of sinking shafts and winzes, and drive them by compressed air brought down in pipes from the surface.

The Koepe system of winding, which appears to be viewed with favour on the Continent, consists in having what is practically an endless rope with one large sheave over the shaft, in the place of the two drums. There are two cages, and the rope below them acts as a counterbalance, so that the load is uniform throughout

The most novel hoisting apparat us is that of Μ. Blanchet (Coal, vol. vi. p. 76), which has now been regularly at work in the Hottinguer shaft at Épinac in France for the last six years. Μ. Blanchet’s method consists in fixing in the shaft a large pipe in which is arranged a piston; from this is suspended a cage carrying waggons. By exhausting the air above the piston the load is gradually forced up by the atmospheric pressure below it. The Hottinguer shaft is 660 yards deep, and the pipe is 5 feet 3 inches in diameter, made up of a succession of cylinders of sheet-iron about ⅛ inch thick and 4 feet 4 inches high, joined by flanges and bolts. The 485 rings composing the long pipe weigh altogether 418 statute tons. The cage has nine decks, and arrangements are made for unloading three at a time; each waggon holds half a ton, so that the total useful load is 4⅜ tons. The speed of hoisting is 20 feet per second. If two hoisting pipes are connected the dead weights may be made to balance each other, and the power required is simply that which is necessary to overcome the weight of the useful load. All the men prefer the pneumatic hoist to the ordinary cage for descending and ascending the mine, and are regularly lowered and raised by it. The advantages claimed by Μ. Blanchet for this system are—(1) the possibility of hoisting from depths at which rope-winding would no longer be practicable; (2) getting rid of the costly ropes and dangers connected with ropewinding; (3) better utilization of the engine power; (4) improvement of the ventilation and diminution of the amount of fire-damp.

10. Drainage.— The mineral having been raised to the surface, the task of the miner might appear to be at an end j but this is not the case, for it is further necessary that he should keep his mine free from water and foul air. These two indispensable operations of draining and ventilating frequently require special appliances which add considerably to the general cost of mining.

In all cases where it is possible, endeavours should be made to keep the water out of a mine, so as to save the expense of pumping it; and the method of putting in a watertight lining (tubbing) in a shaft has been already described (Coal, vol. vi. p. 62). When large streams of water happen to be intersected by underground workings, and threaten to overpower the available pumping machinery, or when it is advisable to save the expense of draining abandoned workings, the entry of this water into the mine may often be prevented by stoppings, called dams, constructed of timber or brickwork.

In spite of all precautions, the miner generally has to contend with water which percolates into the workings. Four methods of getting rid of this water are available, viz., adits, siphons, winding machinery, and pumps.

An adit, day-level, or sough is a nearly horizontal tunnel with one end opening at the surface, allowing the water to drain away naturally. In hilly countries mines are often worked entirely by adits, and even when a mine is deepened below the drainage level the utility of the adit is still threefold :—it lessens the quantity of water which tends to percolate into the lower workings; it lessens the depths to which the water has to be pumped; and, by furnishing a certain amount of fall, it enables water to be applied as power. On account of these important advantages some very long and costly adits have been driven for the purpose of aiding the miners in certain metalliferous districts.

Thus in the Harz the Ernest Augustus adit (“Ernst August Stolln ”) has been driven a distance of nearly 6⅛ miles into the Klausthal district. The total length of the adit, including the branches, is no less than 14 miles. It intersects many of the lodes at a depth of upwards of 400 yards from the surface. The total cost of this adit is estimated at £85,500.

Another long adit is the celebrated “Rothschönberger Stolln,” which unwaters some of the most important mines at Freiberg in Saxony. The length of the main or trunk adit is more than 8⅛ miles; the gradient of the greater part of it is only 1 ’ 18 inch in 100 yards. The branches of this adit among the mines are more than 16 miles in length, so that the total length of the main adit with its branches amounts to nearly 25 miles. Many of the mines are now drained naturally to a depth of 250 to 300 yards. The cost of the main tunnel was £359,334, or nearly £24 per yard, but this includes the cost of eight shafts, heavy expenses for pumping from these shafts, the walling of the adit for ∣ mile, and all general expenses. The length of time occupied in driving this adit was thirty-three years. The “Kaiser Josef II. Erbstolln” in Hungary is another remarkable mining tunnel, which was commenced in 1782, and completed in 1878 at a total cost of 4,599,000 florins. It is 10^ miles in length, extending from the valley of the river Gran to the town of Schemnitz, where it intersects the lodes at depths varying from 300 to 600 yards according to the contour of the surface.

In Cornwall the Great County adit was driven for the purpose of relieving the Gwennap mines of their water, and it was pushed on nearly to Redruth. This adit differs from the great works undertaken in Germany by the fact that it commences in the mining district, and, though the length of all the drivages amounts to more than 30 miles, the water from the most distant mine does not run more than about 6 miles before reaching daylight. The average depth is only 70 or 80 yards from the surface. In fact this great adit, though a work of great utility when the Gwennap district was in a flourishing condition, is merely a network of comparatively shallow drivages, often along the lodes themselves, among the mines, and therefore for boldness of execution cannot for one moment be compared to the great Schemnitz, Freiberg, and Klausthal drainage tunnels which have just been mentioned. The Blackett Level in Northumberland is an adit which has been driven a distance of about 4f miles, and it will have to be extended about 2 miles further before reaching Alienheads. Its depth from the surface at this plaoe will be about 200 yards.

The main part of the Halkyn tunnel in Flintshire is 2 miles 1256 yards in length, and the branch driven out to Rhosesmor mine intersected the vein at a distance of 809 yards, making a total of about 3⅜ miles. The greatest depth from the surface is 230 yards, and the average depth in Halkyn Mountain about 215 yards. The length and depth of this adit are not remarkable; but the great quantity of water discharged is a point of considerable interest and importance. It is estimated that this adit is now discharging 15 million gallons or 66,000 tons of water in twenty-four hours, although the outflow is purely natural, for no mines are pumping water into. it. It is now easy to understand that the Rhosesmor mine, though provided with powerful pumping machinery, was unable to cope with the springs it encountered.

In the United States the famous Sutro tunnel is an adit of which the main branch, 4 miles in length, reaches the great Comstock lode in Nevada at a depth of 1700 feet. The total cost of this tunnel, which λvas completed in nine years, is estimated to have been $7,000,000. The quantity of water running out daily in 1879 was 12,000 tons, at a temperature of 123° Fahr, at the mouth of the tunnel. All this water must otherwise have been pumped to the surface at a cost estimated at $3000 a day. The obstacles to progress were very great: not only was the heat extreme, but swelling ground was encountered which snapped the strongest timber. Thanks, however, to the untiring energy of Mr Adolph Sutro, the difficulties were at last successfully overcome, and this great work will long remain as a monument to his foresight, skill, and patient pertinacity.

The Atlantic-Pacific tunnel, which was commenced in 1880, will pierce the heart of the Rocky Mountains under Grey’s Peak, Colorado. It is being driven from both sides of the watershed, and will have a total length of 4f miles from end to end.

Siphons have been used for unwatering workings in special cases; but of course they will not act unless the barrier over which the water is raised is very decidedly less than 33 feet.

When workings cannot be drained by tunnels or siphons it is necessary to raise the water mechanically, either to the surface or at all events to an adit through which it can flow away naturally. If the amount of water is not too considerable, it is often convenient to use the winding machinery and draw up the water in special buckets (waterbarrels) or tanks. The bucket may be tilted over on reaching the surface, or it may be emptied by a valve at the bottom. This means of raising water is often adopted while sinking shafts, when it may be desirable to wait till the whole or a portion of the shaft is completed before putting in the final pumping machinery.

The varieties of pumps used in mines are numerous. In small sinkings hand-pumps, either direct-acting or rotary, may be applied; steam-jet pumps on the principle of the Giflard injectors are also used; and pulsometers, though requiring a large expenditure of steam, have the advantages of being quickly fixed, of occupying little space, and of working with sandy or muddy water. They are capable, therefore, of rendering great services in special cases. When we come to the definitive machinery erected in large mines of considerable depth, we find that the prevailing types of pumps are few. They may be classified as follows :—(A) lifting and force pumps worked by rods in the shaft actuated by wind, water, or steam power; (B) force-pumps at the bottom of the shaft worked by steam, compressed air, or hydraulic pressure.

A. In describing the first method we have to consider the motive power, the rods, and the actual pumps themselves.

Windmills have the disadvantage, which is often fatal, that the power is not constant. By erecting an auxiliary steam-engine, which can be set to work if wind fails, this evil is overcome; and at the Mona mines in Anglesea a windmill pumps up water from a depth of 80 fathoms at the rate of upwards of 90 gallons per minute. As the site of the mine is breezy, there is wind enough to work the mill about one-half of the time.

Water-power was for a long period the principal agent employed in draining mines, and it is still of the greatest utility in many districts, reservoirs being constructed to collect and store the rainfall. Some idea of the scale upon which these works are conducted will be gathered from the following figures relating to the Harz mines. In 1868 there were “sixty-seven reservoirs covering an area of 604 acres, and having a storage capacity of 336,000,000 cubic feet.” ® The total length of the various leats, races, and other water-courses, including the six principal adits, is about 170 statute miles. The net power extracted is reckoned at 1870 horse-power, but less than one-fourth of this is used for pumping.

Water-power is applied to pumping machinery by water-wheels, turbines, and rotary or non-rotary water-pressure engines. Excepting the case of the latter, the rotary motion has to be converted into a reciprocating motion by a crank; and furthermore with turbines the speed must be reduced very considerably by intermediate gearing.

Overshot wheels are the commonest prime movers when pumps are worked by water-power; water-wheels are frequently constructed 40 or 50 feet in diameter, and at the Great Laxey mine, in the Isle of Man, one of the wheels is no less than 72 feet 6 inches in diameter and 6 feet in the breast. The power is conveyed from the waterwheel by a connecting rod to a bell-crank (bob) placed over the shaft; and when, owing to the contour of the ground, the wheel has to be placed at a distance, it is connected to the bob by the so-called flat rods, made of wood, bars of iron, or wire-rope, travelling backwards and forwards, and supported by pulleys or oscillating upright beams.

Water-pressure engines have the advantage of being able at once to utilize any amount of fall, and those which are direct-acting can be applied immediately to the main rod of the pumps.

Steam, however, is the power used par excellence in draining mines; indeed the first applications of steam-power were made for this purpose, and Watt’s great inventions owed their birth to the necessities of mines which could no longer be drained by the waterpower at their command.

The principal type of engine is that known as the Cornish engine, which is a single-acting condensing beam engine working expansively. Its mode of action may be briefly described as follows. The steam is let in at the top of the cylinder and presses down the piston, which is connected with one end of a large beam, whilst the main rod of the pumps is attached to the other. When the piston has completed its course the equilibrium valve is opened by a cataract, and, the pressure on both sides of the piston being now equal, the weight of the pump rods, or rather the excess of their weight over that of the counterbalances, causes them to drop and force up the water from the mine by means of the plungers, which will be described immediately. Double-acting rotary engines working the pumps by cranks may also be met with.

The rod in the shaft, known as the main rod or spear rod, is usually made of strong balks of timber butted together and connected by strapping plates fastened by bolts. It serves to work either lifting-pumps or force-pumps, or both.

The lifting-pump, or drawing lift (fig. 87), consists of the windbore, the clack-piece, the clack-seat piece, the working barrel surmounted by pumps, and the bucket with its rod. The whole works like any ordinary pump, and needs no special explanation.

The force-pump used in mines, known as the plunger-pump, consists of a solid piston (plunger) (fig. 88) working through a stuffing-box in a pump standing on the H-piece. This has a valve which communicates with the windbore resting in the cistern. Above the H-piece comes the door-piece with another valve, and then a series of pipes, generally of cast iron, but occasionally of wrought iron, constituting the column. The upward motion of the plunger, which is attached to the main rod, causes an inflow of water, which is forced into the column when the plunger descends. It is usual to fix a drawing lift at the bottom of the shaft, which raises the water into a first cistern, and thence a plunger forces it into a second cistern some 60 yards higher up; and it is continually forced up from cistern to cistern until it reaches the adit or the surface.

There are numerous important matters which require special attention, such as the valves, catches, balance-bobs, guiding arrangements for the rod in inclined shafts, the V-bobs, fend-off bobs, and running loops, which have to be used when there are bends in the shaft; but space will not permit of more than mere mention of these details.

Such then is the standard arrangement worked by steam or water power for pumping from mines. The great advantage of the system consists in the employment of the plunger, because it is simply necessary for the machine to raise a weight slightly greater than that of the water, which is forced up afterwards by the downstroke of the rods. Leaks are readily discovered, and the stuffingbox can be easily screwed up as the packing wears; this is one great reason of the superiority of the plunger compared with a piston working in a barrel.

The modifications of this system relate more to the engines employed than to the actual pumps themselves.

The cylinder of the Cornish engine is sometimes reversed and stands over the shaft, the main rod being attached directly to the piston. This type of engine, known as the Bull engine in Cornwall, dispenses with the ponderous beam, but it has the great disadvantage of obstructing the mouth of the shaft. The use of two cylinders combined, as invented by Woolf, causes less strain upon the main rod and pumps (pit-work) and machinery generally, as the initial velocity of the piston is smaller and the engine starts with less jerk. The cylinders are placed side by side or one above the other.

Kley, of Bonn, has constructed engines on the Woolf system with steam acting on both sides of the pistons. He makes the excess of the weight of the rod over that of the counterbalances sufficient to raise only half the weight of the water and to overcome the friction; and then in the descending stroke the steam acts on the top of the piston and so makes up for the insufficiency in force of the rods. As the steam acts on both sides of the piston the same amount is consumed, it is true, but a smaller cylinder will do the work, and the original cost of the engine is lessened. The same engineer of late years has put up several pumping engines in Belgium, Germany, and France of 30 to 560 horse-power, with a fly-wheel which serves simply to regulate the stroke of the piston, so that the crank always stops before or after the dead point till the cataract starts another stroke. The engines are double-acting, -with two cylinders and beam. The advantage of working with the fly-wheel is that the main rod and pumps are set in motion without the injurious jerk unavoidable with a Cornish engine worked at a high rate of expansion.

Μ. Guinotte, tne well-known Belgian engineer, also adopts a fly-wheel, and the engines he has erected at Mariemont and elsewhere are single-acting rotary engines with one cylinder. The peculiarity of the fly-wheel is that he can weight it in any way he pleases; and he so overcomes the difficulty, which occurs in other rotary machines, of its being impossible to work them below a certain speed. His object has been to make the speed slow at the beginning and end of a stroke, so as to avoid the injurious shocks to the valves and machinery generally from sudden starts and stoppages. In order to make the main rod act by traction only and not compression, which may be advisable with iron rods, the plungers are sometimes reversed; whilst Kraft of Seraing has introduced the Rittinger pump, which consists of a hollow moving plunger with a valve inside, and a plunger case above it working over a hollow fixed plunger. By this arrangement both the up and the down stroke of the engine cause water to be forced up; and this pump is used with a double-acting rotary engine.

B. We must now speak of the second class of pumps, viz., force- ≡ worked by steam, water-power, or compressed air at the ι of the shaft.

The steam pumps are of very various descriptions, but they mostly consist of one or two plungers, or rams, set in motion by a rotary or a non-rotary engine, which may or may not work with expansion and condensation. The plunger or ram is generally fixed directly on to the piston, and works in the same line, consequently the power is transmitted to the plunger with the least possible loss. The water is forced up the shaft in one long column. Engines and pumps of this kind are easily kept in order; all the parts are readily accessible. The miner is able to dispense with the heavy beam, the massive engine-house, the long main rod and its connexions and bobs, the various cisterns and plungers, and instead he has a compact and easily supervised machine and a simple line of pipes taking up but little space in the shaft; the pump can therefore be erected and set to work very quickly, and this is a matter of the utmost importance in emergencies. It is true that these direct-acting steam-pumps, even when worked by a compound engine, cause a greater consumption of coal than the Cornish engine; but, as a set off, there is the economy in first cost, erection, and repairs which has led to their adoption more especially in collieries. The steam is generated by boilers underground, or is conveyed from the surface in well-jacketed pipes.

If natural water-power is available water-pressure engines working the plunger directly are often employed, and indeed such water-power may be created artificially for use in workings where steam-power is objectionable on account of the heat. There are other reasons too for employing water for transmitting power; where the length of the rods is very great, and they have to be worked quickly, there is a great liability to breakages; inorder to overcome these difficulties at the mines on the Comstock lode, Mr Joseph Moore uses a steam-engine at the surface to work an hydraulic accumulator, and then by pipes conveys the water under pressure to hydraulic engines working plungers. These are fixed at 2400 feet from the surface, and force the water in one column, 813 feet high, to the level of the Sutro tunnel. The exhaust water is returned to the surface in pipes and used over again. The pumps are now raising 1600 to 1700 gallons per minute.

Where compressed air is being supplied to a mine for drilling and winding purposes, it is often convenient to employ it, by means of direct-acting pumps, such as are generally used with steam, for the drainage of small temporary sinkings; and occasionally large pumps raising considerable quantities of water are worked in this way.

11. Ventilation and Lighting.— The composition of the air of the atmosphere is about one-fifth by volume of oxygen and four-fifths of nitrogen, with a little carbonic acid gas; more exactly, the standard amount of oxygen may be taken at 20 ’ 9 per cent., and that of the carbonic acid gas at 0Ό3 per cent. The atmosphere of mines is subject to various deteriorating influences: not only do noxious gases escape from the rocks into the underground excavations, but also the very agents employed in the execution of the work itself pollute the air considerably.

The dangerous emanations of fire-damp in collieries have been already described (Coal, vol. vi. p. 72); and with reference to this gas it is simply necessary to say that its presence i·s not entirely confined to coal mines. Large quantities have been observed in Silver Islet mine, Lake Superior, where several explosions have occurred, whilst small quantities are met with in the stratified ironstone of Cleveland, and also in the Cheshire salt mines; jets of the gas may be seen constantly burning in the salt mine at Bex in Switzerland; a little has been noticed also in lead mines in Wales and Derbyshire. In the Sicilian mines the amount given off by the black carbonaceous shales interstratified with the sulphur beds is sufficient to cause dangerous explosions. It has been pointed out (vol. vi. p. 72) that carbonic acid gas exudes from coal; it escapes also from some mineral veins. At the lead mines of Pontgibaud in central France it is so abundant that special fans have to be provided for getting rid of it; very distinct issues of this gas may be observed at the Foxdale mines in the Isle of Man, and in the Alston Moor district it is not uncommon. This gas is likewise given off in the Sicilian sulphur mines, where also the highly poisonous sulphuretted hydrogen is of frequent occurrence, the water in the workings being often saturated with it. Small quantities of mercurial vapour occur in quicksilver mines.

Such then are the principal gases which naturally pollute the atmosphere of mines, and have to be swept out by ventilation. In addition to these we have the products of the respiration of the men and animals in the pit, and those due to the combustion of candles or lamps, and the explosion of gunpowder, dynamite, àc.

Dr Angus Smith reckons that two men working eight hours, and using ⅜ lb of candles and 12 oz. of gunpowder, produce 25’392 cubic feet of carbonic acid (anhydride) at 70° F.,—viz., 10 ’ 32 by breathing, 12’276 by candles, and 2’796 by gunpowder.

The products of the explosion of gunpowder have been carefully studied by Captain Noble and Sir Frederick Abel, and the following figures, showing proportions by weight, are copied from the valuable paper containing the results of some of their researches:— [table]

The solid residue of the mining powder consisted mainly of potassium carbonate, potassium monosulphide, and sulphur. The percentage composition by volume of the gas produced was :— [table]

The volume (calculated for a temperature of 0° C. and barometer· 760 mm. of mercury) of permanent gases generated by the explosion of 1 gramme of dry powder is— [table]

M.M. Sarrau and Vieille have communicated to the Academy of Sciences the results of their researches concerning the decomposition of certain explosives, and more particularly gun-cotton and nitrated gun-cotton. The following table shows, in litres, the volume (at 0° C. and 760 mm. of mercury) of each of the gases per kilogramme of the substance exploded in a closed vessel :— [table]

If, however, the explosive is decomposed at a pressure approaching that of the atmosphere, the volumes (again at 0 β C. and 760 mm. of mercury) are very different, as shown below:— [table]

When explosives are decomposed in this way they liberate nitric oxide and carbonic oxide, and the analyses of MM. Sarrau and Vieille confirm the practical experience of miners, who complain greatly of noxious fumes when, owing perhaps to a bad detonator, a charge of dynamite or tonite fails to explode properly.

The air of mines is finally deteriorated by organic matter contained in the exhalations of the men and animals employed and in the products of decaying timber, by dust, and by the solid particles constituting the smoke of explosives. It must be recollected also that the injury to the air is not confined to the addition of the gases and substances just mentioned; but the proportion of oxygen is diminished by the combustion of candles, by respiration, the decay of timber, and decomposition of some minerals such as iron pyrites. Dr Angus Smith sums up the results of his analyses of the air of British metal-mines as follows :— [table]

He considers air with 20 ’ 9 per cent, oxygen as normal, and air with proportions between that and 20’6 as impure; and where the percentage of oxygen descends below 20’6 he calls the air exceedingly bad. According to these standards, only 10’67 per cent, of the samples showed the air to be normal or nearly so; 24 ’69 per cent, were decidedly impure; whilst 64 ’63 per cent, or nearly two-thirds of the samples were exceedingly bad. The amount of oxygen in one specimen was as low as 18’52 per cent., whilst the carbonic acid often exceeded 1 per cent, and in several instances 2 per cent. It is evident that twenty years ago the ventilation of British metal mines was anything but satisfactory, and even now there is room for improvement.

Having explained the reasons why the air of mines must be constantly renewed, we must now point out how this desirable end is effected.

Two systems are employed,—natural ventilation and artificial ventilation; but, as both systems have been described (Coal, vol. vi. p. 70), little remains to be said here, especially as the ventilating machines in metalliferous mines generally cannot for one moment be compared with the powerful appliances employed in collieries. In veinmining there are generally many more shafts than in collieries, and natural currents are set up which are often considered sufficient for ventilating the mines; nevertheless, the advanced workings, such as the ends, rises, and winzes,—in fact all workings in the form of a cul-de-sac,— are likely to require special means of ventilation as soon as they proceed a little distance from the main air-current.

The means of ventilating a drift or heading are various. If a natural or artificial draught exists at the mouth of the drift, it may be diverted by an upright partition (brattice), or an air-way may be constructed along the roof or floor by a horizontal partition of planks (air-sollar) (fig. 89). In this way a sufficient supply is secured at the end or fore-breast.

The water-blast is another simple appliance; it is precisely the same as the well-known tromp, and it blows a current of air through square pipes made of boards, or better through cylindrical pipes of sheet zinc.

The fall of water may be applied by Williams’s water-jet, shown in fig. 90. The jet of water acts like an injector, and creates a powerful current.

Small fans driven by boys, or better by small waterwheels or other machinery, are frequently applied, and the Harz blower (duck machine, Cornwall) (fig. 91) is not uncommon. This is merely an air-pump of very simple construction which is worked by the main rod of the pumps, and can be arranged so as to exhaust the foul air or force in fresh air.

In working in blasting ground, boring-machines driven by compressed air are becoming more and more largely used every day, and the exhaust air escaping from the machines is invaluable for ventilation. At the same time, on account of volley firing, the quantities of deleterious gases generated in a short space of time are very considerable; and, in order to get rid of them speedily, the compressed air may be utilized for working a Körting aspirator or the somewhat similar ventilator of Mr Teague, a jet of compressed air turned into a ventilating pipe, which creates an exhaust (fig. 92). Naturally this ventilator is merely brought into play at the time of blasting, and while the boring machinery is out of use. When compressed air is being supplied on a large scale to a mine for boring and winding machinery, it is often convenient to convey it by a small gas-pipe to working places in which the ventilation is inadequate. Of course, in one sense, it is very uneconomical to compress air to a pressure of 60 or 70 lb to the square inch for ventilating purposes only; but, where compressing machinery is always at work on the mine, it may be better to be a little wasteful of cheap power at the surface than to go to the greater expense of having a man or boy to work a fan underground.

Mines are lighted by lamps, torches, candles, and electricity. The subject of safety lamps for fiery mines has already been discussed (see Coal, vol. vi. p. 72), and consequently the question of illuminating mines may be treated in a very summary manner.

Lamps vary very much in shape and size. The Sicilian miner has a mere shallow cup of unglazed pottery; the Saxon a small tin or brass lamp in a wooden box lined with tinplate and open in front. In the Harz the miner prefers a heavy flat iron lamp with a hook by which it is stuck into the timber or any crack in the rocks; in France, northern Italy, and parts of Spain, the iron lamp is lenticular in shape and also suspended by a hook. In Scotland, and parts of Germany and the United States, a small tin lamp of the shape shown in fig. 93 is very common; the hook enables it to be carried on the hat while climbing ladders, and to be fixed up underground. Olive oil and rape oil are burnt in these lamps; petroleum lamps are employed occasionally.

The miners of England and Wales still cling to the tallow candle; and when surrounded by a lump of clay it can easily and quickly be fixed in the working place or carried upon the hat when climbing. Gas brought down from the surface answers for illuminating large excavations, such as on-sétting places and engine-rooms.

Up to the present time the electric light has been but little used underground on account of its want of portability, and the smallness of the spaces requiring illumination. Very often a few men only are employed in each working place, and consequently the expense incurred in fixing and shifting the lamps and maintaining them alight would be out of proportion to the value of the work executed. However, an incandescent electric lamp has been invented weighing only 10 lb, which gives the light of three candles for six hours, and it may be reasonably expected that improvements will be made which will render the electric light more available for underground purposes than it is at present. When the area requiring illumination is large, an arcrlamp may be used with advantage.

Among the first successful applications of electric lighting to underground excavations may be mentioned that of Μ. Blavier at the Angers slate quarries. In the year 1879 he fixed two Seιτin lamps in one of the large underground chambers with an area of 2400 square yards, and he found that they gave light enough for all the men at work. The total cost, reckoning everything, viz., coal, carbons, repairs, labour, depreciation of plant, and interest on capital, is 50 francs per day; the gas formerly in use cost 54 francs a day and gave much less light. It is evident, however, that the arc lights can only be applied with advantage in special cases where a large number of men are concentrated in one working area which can be illuminated from one or two points.

The large chambers in the salt mine of Maros-Ujvar in Hungary have been regularly lighted up by electricity since 1880. The cost is somewhat greater than that of the tallow, oil, or petroleum formerly in use; but, on the other hand, the illumination is better, the men can do more work and are more easily supervised, whilst the air of the mine is not deteriorated by the products of combustion of the lamps.

12. Means of Descending into and Ascending fτ<ym Mines. —Where mines are worked by adit-levels the men naturally walk in along the ordinary roadways; such mines, however, are exceptional, and the men generally have to climb down and up by ladders, or are raised and lowered by machinery. The means of access to and from workings may be classified as follows :—(1) steps and slides; (2) ladders; (3) cages; (4) man-engines.

If a lode or seam is inclined at an angle or 40° or 50° from the horizon, steps may be cut in the floors of the deposit if it is firm enough, or wooden stairs may be put in with a hand-rail. Even with higher dips steps may be arranged by directing them in a line intermediate between the dip and the strike. In speaking of conveyance underground, reference has already been made to the practice of carrying sulphur ore in Sicily and slate in Germany up to the surface by steps; and steps may be found in other foreign mines and occasionally in Great Britain. They are much less fatiguing than ladders placed so flat that part of the weight of the body rests upon the arms. In some of the Austrian salt mines the men descend by wooden slides inclined at angles varying from 30° to 50°, flattening at the bottom to destroy the velocity gradually; the ascent is effected by steps.

Ladders are very largely used in metal mines all over the world, but they vary a good deal in different countries. The ladder consists of two sides and a series of rungs (staves, Cornwall). The sides are usually made of wood, and the rungs of wood or iron. The distance between the rungs is important; 10 inches from centre to centre is sufficient, for climbing upon ladders with the rungs 12 inches apart is decidedly more fatiguing. On the Continent wooden rungs are commoner than iron ones, and oak is preferred. Sometimes the wooden staves, instead of being round, are flat, so as to stand more wear, and iron sides may be seen in places where dry rot is very bad. Platforms should be fixed at short intervals, not exceeding 3 or 4 fathoms in perpendicular shafts, so as to prevent falls from having fatal consequences.

In many cases sufficient attention is not paid to the angle of inclination of the ladders. A ladder is climbed with the least fatigue when the person uses his arms simply to steady himself, and is not compelled to pull himself up by them, as on a vertical ladder, or to support much of the weight of his body by them, as happens with a very flat one. The best angle is about 20° from the vertical, and in Belgium the authorities have very wisely decreed that no ladder shall be inclined at an angle of less that 10° from the vertical. Furthermore, of the two arrangements shown in fig. 94 A is better than B, because it not only affords a greater inclination for the ladders, but also renders it less likely that a man will drop through the opening (manhole) in the platform (sollar) if he loses his hold and falls. These may seem trifling matters; but, leaving aside the question of safety, the economy derived from fixing the ladders at the best inclination is by no means small. To make this apparent we must recollect the depths to and from which men have to climb, viz., 300, 400, and even 500 yards. It is important, therefore, to save every unnecessary expenditure of energy, which, though trifling for one ladder, becomes considerable when repeated a great number of times. When a mine has reached a depth of 200 yards, and a fortiori when it exceeds it, mechanical appliances should be introduced for raising and lowering the men, because time and strength are wasted by climbing. Medical men also are agreed that excessive ladder-climbing is injurious to the health of the miner. Therefore, both upon hygienic and financial grounds, one of the first thoughts in working a mine should be the conveyance of the men up and down the shafts by machinery with the least possible fatigue.

In collieries and other mines worked by perpendicular shafts, it has long been customary to raise and lower the men by the ordinary winding machinery already described. In the United Kingdom it is necessary that guides should be used if the shaft exceeds 50 yards in depth; safetycatches and disengaging hooks (Coal, vol. vi. p. 75) are frequently applied for the purpose of preventing accidents. The simplicity of this method of ingress and egress naturally renders it popular, and statistics prove that, where proper precautions are used, it is exceedingly safe.

The first man-engine was put up in the Harz in 1833, and nine years later a similar machine was fixed in Tresavean mine in Cornwall. Since that time this very useful means of conveying workmen up and down shafts has been resorted to in other mining districts, and especially in Belgium and Westphalia.

Two kinds of man-engine are in use, the double-rod machine and the single-rod machine. The double-rod or original man-engine consists of two reciprocating rods like the main rods of pumps, carrying small platforms upon which the men stand. The stroke is from 4 to 16 feet, and the little platforms are so arranged that they are always opposite each other at the beginning and end of each stroke.

Figs. 95 and 96 represent the rods in the two final positions. A man who wishes to descend steps upon platform δ (fig. 95); the rod B goes down, and A goes up, so that b (fig. 96) is brought opposite c. The man steps across from b to c, and then the rod A makes a down-stroke, B an up-stroke. Platform c is now opposite d (fig. 95), and the man again steps across; and thus, by constantly stepping from the rod as it completes its down-stroke, the man is gradually conveyed to the bottom of the shaft. By reversing the process, or, in other words, by stepping off on to the opposite platform as soon as the rod has completed its upstroke, the man is raised to the surface, without any fatigue beyond that of the very slight effort of stepping sideways. If each rod makes four up and down strokes of 10 feet each per minute, the rate of ascent or descent will be 80 feet per minute.

The single-rod man-engine has one rod carrying steps, whilst fixed platforms are arranged in the shaft so as to correspond exactly with them (fig. 97). If a man wants to go down, he steps on to A when the up·stroke is completed; the rod goes down and A is brought,down opposite to the fixed platform b, on to which he steps off. He then waits on b until the rod has finished its up-stroke. B is brought opposite b ; he steps on to B, the rod goes down and he is brought opposite c, where he steps off again and waits. By reversing the operation he is gradually lifted to the top of the shaft. The singlerod engine may be used, by men going up while others are going down, provided that there is sufficient room upon the fixed platforms (sollars). The best plan is to have sollars right and left, as shown in the figure, and then the ascending men step off to the left, for instance, while the descending men take the right-hand sollars. The ascending man steps on to the man-engine as soon as the descending man steps off, and so the rod may be always carrying men up or down. The usual stroke in Cornwall is 12 feet, and there are from three to five or six strokes a minute. With five strokes the men descend 10 fathoms a minute, or in other words a descent or ascent of 300 fathoms occupies half an hour. The reciprocating motion is best obtained from a crank, because in this case the speed is diminished gradually at the dead points, and the danger of an accident in stepping off and on is thereby diminished; man-engines, however, are sometimes driven by direct-acting engines.

Man-engine rods are constructed of wood or iron; and at Andreasberg in the Harz each rod is replaced by two wire ropes. Like a pump rod the man-engine rod requires proper balance bobs and catches, and for the safety of the men a handle is provided at a convenient height above each step.

The man-engine has one great advantage over the cage, which consists in the fact that it can be safely applied in inclined and even crooked shafts; and it is for this reason that man-engines have been adopted in many metal mines unprovided with vertical shafts.

Careful comparisons as regards safety of travelling have been made in Prussia between ladders, man-engines, and cages. The average accidental death-rate is shown by the accompanying table, which gives averages for a period of ten years, 1871 to 1880:— [table]

The table shows that the cage is nearly as safe as ladders. In reality, if the actual distance travelled were taken into account, the cage would appear to be safer, because we may fairly assume that the mines in which men are hoisted by cages are on the whole very much deeper than those in which men ascend and descend by ladders. The man-engine appears to be decidedly more dangerous than either the cage or ladders. Here again a distinction requires to be made between the single-rod and the double-rod machines, and the Prussian statistics include many of the latter. It will be readily understood that a fall in a naked shaft with few fixed platforms is much more likely to be fatal than a fall in the shaft of a single-rod man-engine which is closed with the exception of the manhole at intervals of 12 feet. The Belgian warocquères are rendered safer than the Harz or Saxon man-engines by having a railing round the back of each platform on the rod. Some of the double-rod machines are made with large platforms so that two persons can stand on them, one going up and the other going down, or both travelling in the same direction. The use of double-rod man-engines has been entirely abandoned in the United Kingdom. The death-rate from accidents on man-engines in Cornwall and Devon during the nine years 1873 to 1881 was 0Ί7 per 1000 persons using them, whilst the annual death-rate per 1000 persons using ladders was slightly higher, viz., 0’19. If the actual distance travelled were taken into account, the scale would turn more decidedly in favour of the man-engine.

The cost of raising and lowering men by the man-engine is not great. At Dolcoath, a tin mine in Cornwall approaching 400 fathoms in depth (see figs. 62, 63), it is reckoned thatl⅜d. per man per day covers all expenses, including interest upon the capital expended and depreciation of plant.

13. Dressing or Mechanical Preparation of Ores.— In a large number of cases the mineral, as it is raised from the mine, is not ready for sale. It usually requires to be subjected to mechanical processes whereby the good ore is entirely or partly freed from valueless veinstone. These processes, which in a few special instances are aided by calcination in furnaces, are known as the dressing or mechanical preparation of the ores. As a rule the valuable ore is specifically heavier than the veinstone, and most of the separating processes are based upon the fact that the heavy particles of ore will fall in water more quickly than the light particles of veinstone.

The processes of mechanical preparation may be classified as follows :—(1) washing and hand-sorting; (2) disintegration, or reduction in size; (3) classification by size or by equivalence; (4) concentration.

(1) Sometimes the ore coming from the mine requires simply to be freed from adhering particles of clay in order to be rendered fit for sale, at other times the washing is necessary as a preliminary process previous to sorting by hand. The operation is performed either by raking the ore backwards and forwards upon a grating under a stream of water, or in a box containing water, or, thirdly, by means of an inclined revolving iron drum worked by hand or any other motive power. The machines used for this purpose, known as washing trommels, are revolving cylinders or truncated cones of sheet-iron provided with teeth inside. The ore is fed in at one end, is subjected to the action of a stream of water, and is discharged at the other end.

The stuff, i.e., the mixed ore, veinstone, and country rock, having been cleansed, it is now possible to make a separation by hand. Women and children are generally employed for this work, as their labour is cheaper and their sight sharper than that of men. The stuff is spread out on a table, and various classes are picked out according to the nature of the products furnished by the mine. Thus in a lead mine we may have—(a) clean galena, (δ) mixed ore, i.e., pieces consisting partly of galena and partly of barren veinstone, (c) barren veinstone and country rock. This is a most simple case; very frequently we have to deal with a vein producing ores of two metals, especially in the case of lead and zinc, and then the classification into various qualities becomes more complicated.

(2) Reduction in size is necessary for two reasons. Even when an ore is sufficiently clean for the smelter, the large lumps are often crushed by the miner for the sake of obtaining a fair sample of the whole, or supplying a product which is at once fit for the furnace. The chief reason, however, for disintegration lies in the fact that the particles of ore are generally found enclosed in or adhering to particles of barren veinstone.

The disintegration is effected by hand or by machinery. Large blocks of ore and veinstone are broken by men with large sledge hammers, and the reduction in size is continued very often by women with smaller hammers. Sometimes the blow of the hammer is directed so as to separate the good from the poorer parts, and hand-picking accompanies this process, called cobbing. Ore may be crushed fine by a flat-headed hammer {bucking iron) on an iron plate.

The machines used for reducing ores to smaller sizes are very numerous; here it is impossible to do more than briefly call attention to those most commonly used. These are stone-breakers, stamps, rolls, mills, and centrifugal pulverizers.

The stone-breaker, or rock-breaker, is a machine with two jaws, one of which is made to approach the other, and so crack any stone which lies between them. The best-known stone-breaker is the machine invented by Blake, which has rendered inestimable services to the miner for the last twenty years, and the introduction of which constituted a most important step in advance in the art of ore-dressing. Its mode of action is very simple. When the shaft A (fig. 98) revolves, an excentric raises the “pitman” B, and this, by means of the toggle-plates C, C, causes the movable jaw D to approach the fixed jaw E by about ∣ inch at the bottom. When the pitman descends the jaw is drawn back by an india-rubber spring. The jaws are usually fluted, the ridges of one jaw being opposite the grooves of the other, and they are so constructed that the wearing parts are quickly and easily replaced.

Mr Marsden of Leeds has lately introduced a pulverizer, constructed on the principle of the stone-breaker, which will reduce large stones to the finest powder in one operation. The moving jaw has an up-and-down as well as the old backwards-and-forwards motion, and the stones are first cracked and then ground by the double action.

Stamps are pestles and mortars worked by machinery. The construction of the modern California stamp mill with revolving heads is explained in Gold, vol. x. p. 747, and the description need not be repeated. In Cornwall the older form with rectangular heads still prevails.

It is impossible to give any correct average figures representing the work done by a stamping mill, because this varies with the hardness of the stuff treated and the fineness to which it must be reduced. However, it is usual in Cornwall to reckon 1 ton of tinstuff and in California 1 to 1∣ ton of gold quartz stamped per horse-power in twenty-four hours.

Stamps are principally used in dressing the ores of gold, silver, and tin, but are occasionally employed for those of copper and lead. The stamps described at vol. x. p. 747 act simply by gravity. Another form, which has met with favour in the Lake Superior district, is the direct-acting or Ball stamp, which works like a steam hammer, the blow of the head being assisted by the pressure of steam. At the Calumet and Hecla Mill, Lake Superior, each Ball stamp is capable of crushing 130 tons in twenty-four hours. In a third kind of stamps, the heads are lifted by a crank aηd the power of the up-stroke compresses a cushion of air (pneumatic stamps) or a spring, storing up power which makes the down-stroke strike a heavier blow.

Revolving rolls were introduced in the west of England in the early part of the present century to replace bucking by hand. The machine, now often known as the Cornish crusher, consists of two cast-iron or steel cylinders which revolve towards each other, whilst at the same time they are kept pressed together by levers or springs. The cylinders or rolls are generally from 18 inches to 2 feet or 2 feet 8 inches in diameter and 12 to 22 inches wide.

Stone mills constructed like flour mills are employed in some countries for reducing ores to powder; and the arrastra, which consists of heavy stones dragged round upon a stone bed, has rendered good service in grinding and amalgamating gold and silver ores, in spite of its being slow and cumbersome. Edge-runners (Chilian mills) also deserve mention.

Iron mills, known as pans, with grinding surfaces made of chilled cast-iron and arranged so that they can be quickly and easily replaced when worn out, are greatly in vogue in the United States for the treatment of ores of gold and silver; the ore delivered to them is already finely divided, and they are intended, not only still further to reduce the size of the particles, but also and more especially to effect the amalgamation of the precious metals with quicksilver. The pulverizers used in Cornwall for grinding grains of tin ore with a little waste still adhering to them are also iron mills.

The centrifugal pulverizers are machines by which the pieces of ore are thrown with great velocity against bars or arms, or against each other, and so reduced to powder; in other machines iron balls or iron rollers are whirled by centrifugal force against an iron casing and grind any mineral contained inside it. These pulverizers are much less used than stone-breakers, stamps, and rolls for the disintegration of metallic ores.

(3) Classification of a crushed ore into sizes is absolutely necessary in some cases and advisable in others, because the subsequent concentration is dependent upon the fall of the particles in water, as will be presently explained. Classification by size is effected by sieves. Hand sieves and flat sieves placed one above the other have been superseded at most dressing establishments by cylindrical or conical revolving screens known as trommels. These screens are made of wire web or of perforated sheets of metal, and they are often arranged so as to discharge one into the other, so that the ore from a crusher can quickly be separated into classes of various sizes.

With sizes of less than 1 millimetre (- 2 ⅛ inch) trommels are no longer employed, and recourse is had to the so-called separators or classifiers. These are boxes in the shape of inverted cones or pyramids into which the finely crushed ore is brought by means of a current of water; a jet of clean water is often made to rise up in the bottom; the larger and the specifically heavier particles fall and are discharged with a stream of water at or near the bottom, whilst the smaller and specifically lighter particles flow away at the top. The separators do not effect a true classification by size; they merely cause a division by equivalence, a term which will be explained immediately.

(4) We now have to deal with the enriching of the ore, or the concentration of the valuable particles into as small a bulk as is economically advantageous. The concentration is generally brought about by the fall of the particles in water. Occasionally the fall in air is utilized; mercury is employed as a collecting agent in the case of gold and silver, and in a few instances magnetism can be applied.

The concentration in water depends upon the difference in specific gravity of the valuable ore and the waste veinstone or rock. A piece of galena with a specific gravity of 7 ’ 5 sinks to the bottom more quickly than a similar piece of quartz, the density of which is only 2 ’ 6. Nevertheless a large piece of quartz may fall to the bottom as quickly as a small piece of galena. Particles which have equal velocities of fall, though differing in size and specific gravity, are said to be equal-falling, or equivalent. P. von Kittinger shows that a sphere of quartz of ∣ inch in diameter would sink in water exactly as quickly as a sphere of galena of τ ⅛ inch in diameter, and these two particles are therefore equal-falling. Consequently, before we can separate properly by water it is necessary to classify the particles by size, so that equivalence shall not prevent a separation or lessen its sharpness. It is nevertheless true that in the early part of the fall of equivalent grains the influence of the specific gravity preponderates, and the denser particles take the lead; therefore, by a frequent repetition of very small falls, particles which have not been closely sized may still be separated.

The principal machine for concentrating particles of sizes ranging between 1 inch and τ ⅛ inch is the jig or jigger. The hand jigger is merely a round sieve which is charged with the crushed ore and then moved up and down in a tub full of water. The particles gradually arrange themselves in layers, the heaviest on the bottom and the lightest at the top. On lifting out the sieve the light waste can be skimmed off with a scraper, leaving the concentrated product below ready for the smelter or for further treatment. Similar sieves worked by machinery were for a long time employed in dressing establishments, but the introduction of the improved continuous jiggers has led to their abandonment in all works of any importance. The continuous jigger is one of the most useful dressing machines of the present day.

It consists of a box or hutch divided by a partial partition into two compartments; in one is fixed a flat sieve s (fig. 99), which carries the ore, and in the other a piston p is made to work up and down by means of an excentric. The hutch being full of water, the movement of the piston causes the water to rise up and fall down through the ore, lifting it and letting it fall repeatedly. The effect of these frequent lifts and falls is to cause a separation of the previously sized ore into layers of rich mineral at the bottom, light waste at the top, and particles of ore mixed with waste in the middle.

The great value of these jiggers is the continuous discharge of the products without stoppages for their removal. Several methods are in vogue, viz., the end discharge, the central discharge, and the discharge through the meshes of the sieve. With the first, the enriched product lying at the bottom of the sieve passes out through openings at the end of the jigger, and the amount escaping is governed by an adjustable cap or shutter, by which the size of the openings can be increased or diminished at pleasure; the middle product can be discharged by openings placed a little higher up, whilst the waste is washed over the top of the end of the jigger at each pulsation. Very often a first sieve simply separates a concentrated product and discharges the poorer product into a second sieve, where a similar separation is effected. With the central discharge, a pipe is brought up through the bottom of the sieve, and the size of the opening for the escape of the concentrated ore is regulated by a cylindrical cap which can be raised or lowered by a screw. The discharge through the sieve is especially adapted for the finer products from the crusher, though it is also used in some cases for grains up to ∣ inch in diameter. The mesh of the sieve is chosen so that the particles under treatment will just pass through, but above the sieve a layer of clean ore is placed which prevents anything but the heavier particles from being discharged. The pulsations of the water, as before, cause a separation into layers, and the heavy rich particles find their way through the bed and drop into the hutch, whence they can be drawn off through a hole at pleasure. The poorer part passes over a simple sill at the end of the sieve, or to a second sieve if necessary. Three or four sieves are occasionally arranged in a row in one machine.

Fig. 100 is a section through the two sieves of a Harz sand jig. The pistons act in the manner explained by fig. 99.

The smaller sizes are concentrated by a variety of machines. The action of many of them is based upon the behaviour of particles carried down an inclined plane by a thin stream of water. If the gradient of the plane and the strength of the thin current are properly arranged, the denser particles will be deposited and the specifically lighter ones washed away, although they may be equal-falling if allowed to settle in deep water.

The principal machines for concentrating fine sands and slimes are the frame, rotating frame, percussion frame, side-blow percussion frame, revolving belt and Frue vanner, the hand buddle, the round buddle, and the keeve.

The frame is simply an inclined wooden table upon which a thin deposit is formed by the sheet of ore-and-waste-bearitιg water which is made to flow over it gently. The stream is then stopped and the deposit washed off by hand or automatically, and collected in pits for subsequent retreatment by similar appliances if necessary.

The rotating frame is a round table with a very flat convex conical surface; the ore for suspension flows on at one part of the centre and forms a thin deposit which is richest at the top and poorest at the bottom, and this deposit is washed off so as to form two classes by means of jets of water, under which the table passes as it turns round. Concave rotating tables, fed at the circumference, are also employed.

The percussion frame, the Stossheerd of the Germans, is a table suspended by four chains which receives a succession of blows from a cam in the direction of the stream flowing over it; after each blow it bumps against a piece of timber before receiving the next blow. These bumps cause the ore to settle, and after a thick deposit is formed it is dug off with the shovel, the upper end being richer than the middle or the tail.

Rittinger’s side-blow percussion frame is a suspended rectangular table ABCD (fig. 101), receiving blows and bumps on the side and not on the end. A stream of orey water S is fed on at the corner A; clean water W is supplied by the other head-boards H, H, H; and the table is pushed out by cams in the direction of the arrow, and is driven back by a spring so that the cross-piece E strikes against a bumping-block K. The light particles travel down the table much faster than the heavy ones, and take a comparatively straight course; whereas the heavy and richer particles remain on the table, subject to the influence of the side-blows, for a much longer time, and travelling along a curved path reach the bottom at F. The middle class is discharged at G and the poor waste at K. The exact degree of richness of the products can be regulated by altering the pointers, strips of wood which can be turned so as to divide the stream of ore and waste where thought most desirable. The great advantage of this machine over the old percussion frame is its continuous action.

The Frue vanner (fig. 102) may be looked upon as an improved form of Brunton’s simple revolving belt. It is an endless band of indiarubber cloth, flanged on each side, which revolves slowly in the direction of the arrows, whilst at the same time it is shaken sideways by a crank motion. The orey water is fed on at A, clean water at B. The natural path of the particles is down the inclined belt, but the specifically heavier ones settle upon it and are carried upwards. Those that can resist the action of the stream of clean water at B go over the end and are washed off as the belt passes through the tank. The poor stuff falls into the waste launder. The degree of concentration can be regulated by the slope and speed of the belt and the strength of the streams of ore and water. The Frue vanner has the disadvantage that it makes only two classes, rich and poor, without any intermediate product.

The hand buddle is a rectangular wooden box with a sloping bottom. A stream of fine ore and waste suspended in water is fed in at the upper end and gradually forms a deposit on the bed of the buddle. A boy with a broom keeps the top of the sediment smooth, so as to ensure regularity of action. After a thick deposit has accumulated, it is dug out in sections which decrease in richness from the upper end {head) to the lower end (tail).

Round buddles, like rotating frames, are of two kinds, convex and concave. The convex round buddle (figs. 103 and 104) is a circular pit with a truncated cone, or head, of varying size in the centre, and a bottom sloping towards the circumference. The orey stream A falling over this head runs down gently, depositing the heaviest particles near the top, the lighter ones further down, whilst the lightest of all flow away at C. The surface of the sediment is kept even by revolving finishes D. This machine may be compared to a number of hand buddles arranged radially round a centre. The deposit that is formed is dug out in rings of varying richness

The concave buddle is a circular pit with the bottom sloping towards the centre. The stream of ore is fed all round the circumference, and runs inwards to the middle, where the lightest particles escape. The rich head is of course near the circumference.

The keeve is a large tub in which the fine stuff is stirred with water and then is allowed to settle from a state of suspension while blows are being struck on the side of the tub. The deposit is afterwards scraped out in layers which increase in richness as they approach the bottom.

The series of processes employed in dressing an ore varies, not only according to the nature of the particular mineral to be concentrated, but also according to the size of its particles and the nature of the other minerals with which it is associated.

With gold the reduction in size is usually effected by stone-breakers and stamps, and much of the metal is then caught by mercury; what escapes is concentrated with its accompanying pyrites by inclined tables covered with blankets, or by buddles, and the concentrate is treated by amalgamation or chlorination. See Gold, vol. x. p. 746.

In the case of silver the ore is frequently pulverized by stamps, and the resulting pulp amalgamated in pans or barrels. The ore may also be concentrated by any of the various machines described, and delivered to the smelter. Many of the ores of silver are sent to the smelting works without any concentration by water, as this would cause a serious loss.

Lead ore is generally crushed by rolls, often after a preliminary reduction in size by the stone-breaker. The crushed ore is classified by revolving screens down to the size of 1 mm., and the resulting grains concentrated by jigging; dredge, or grains of ore and matrix, must be recrushed, sized, and jigged. The finer sizes are classified by pyramidal boxes and concentrated by frames, rotating tables, and buddles.

Zinc ore is dressed in the same way as lead ore; and, as galena and zinc-blende are frequently intimately associated together, it is necessary to separate them by the use of the jig, buddle, and frame.

Tin-bearing rock is crushed by the stone-breaker and then stamped fine. The resulting sand and slime may be concentrated by the repeated use of the round buddle, with the keeve for a final cleaning; but often the sand only is enriched by the buddle, whilst the very finest particles, constituting an almost impalpable mud (slime) when mixed with water, are treated by frames. When much pyrites is present it is necessary to make a preliminary concentration and roast the enriched product (witts) in a furnace. The calcination converts the heavy iron and arsenical pyrites into a light oxide which can be got rid of with the rest of the waste by buddling and framing. The final product from the keeve is clean enough to approach pure cassiterite in the percentage of metal. Alluvial tin ore is concentrated in sluice-boxes, and sometimes by jiggers, after a preliminary treatment in a puddling-machine (Gold, vol. X. p. 745) if there are balls of clay which have to be broken up. When the alluvial ore occurs as a hard conglomerate (cement), it has to be stamped.

Copper ores are treated by crushing by rolls and sometimes stamps, sizing by trommels, and then jigging and buddling; but, as some of the ores are very friable and easily carried away by water, hand-picking is employed to a greater extent than with lead and tin ore, and the enrichment by water is not carried so far on account of the inevitable loss that would ensue. The amount of concentration depends upon the distance from the smelting works, and the mine-owner has to calculate whether it is best to get a low price for a large quantity of ore, after paying the carriage, or a higher price for a smaller lot (parcel) when due allowance has been made for the cost of dressing and loss sustained in that process. Thus, for instance, in Cornwall, the ore containing copper pyrites is dressed so as to contain only from 5 to 8 or 9 per cent, of metal, because it can easily be conveyed to Swansea by sea, and because further reduction in bulk would cause greater loss in value than the saving of freight.

The loss in dressing is very considerable. P. von Rittinger estimates it at from 30 to 50 per cent., and stubborn facts bear out his conclusions. Heaps of refuse from dressing floors are frequently worked over again with profit; and in the year 1881 no less than 909 tons of “black tin” (i.e., concentrated tin ore fit for the smelter), worth £35,283, were extracted from the muddy water allowed to flow away from the dressing floors of some of the principal Cornish tin mines.

The fall in air has been employed instead of the fall in water for concentrating purposes, and several ingenious air-jigs have been constructed and worked upon this principle.

In exceptional cases magnetic attraction may be utilized. Magnetic iron can be separated in this way, and the magnetic process is applied for treating mixed blende and chalybite, the specific gravities of which are too close to render concentration by water practicable. The mixed ore is calcined, and the chalybite is thus converted into magnetic iron, which can be extracted by a magnetic separator, leaving saleable blende.

Before concluding this part of the subject we will briefly enumerate the principal improvements that have been made in metal-mining during the last quarter of a century. They are as follows :—diamond-drill for prospecting; machine drills for driving, sinking, and stoping; use of compressed air for winding underground; stronger explosives, especially the nitro-glycerin compounds dynamite and blasting gelatin; increased use of steel for various purposes; Blake’s stone-breaker and continuous jiggers; extended application of hydraulic mining; larger employment of electricity both for blasting purposes and for signalling by telegraph and telephone. It may be reasonably hoped that ere long electricity will render increased services to the miner for lighting the workings and for the transmission of power.

14. Recent Legislation affecting Mines in the United Kingdom. γ — In England the person owning the surface of a freehold is prima facie entitled to all the minerals underneath, excepting in the case of mines of gold and silver, which belong to the crown. The crown, however, does not claim gold and silver extracted from the ores of the baser metals. The ownership of the minerals can be, and often is, severed from that of the surface, the latter being sold whilst the mineral rights are reserved by the original owner. Local customs, now regulated by Acts of Parliament, are still in force in Derbyshire (High Peak Mining Customs and Mineral Courts Act, 1851, 14 & 15 Vict. c. 94, and the Derbyshire Mining Customs and Mineral Courts Act, 1852, 15 & 16 Vict. c. 43) and in the Forest of Dean (1 & 2 Vict. c. 43, and 24 & 25 Vict. c. 40). The Stannaries Act (32 & 33 Vict. c. 19) regulates the commercial dealings of mining companies in Cornwall and Devon, and provides for their liquidation.

The working of mines in the United Kingdom is controlled by five Acts of Parliament, viz., “The Coal Mines Regulation Act, 1872” (35 & 36 Vict. c. 76), “The Metalliferous Mines Regulation Acts, 1872 and 1877” (35 & 36 Vict. c. 77, and 38 & 39 Viet c. 39), “The Stratified Ironstone Mines (Gunpowder) Act, 1881” (44 & 45 Viet, c. 26), and “The Slate Mines (Gunpowder) Act, 1882” (45 Vict. c. 3). The last three Acts simply refer to the annual returns, and exemptions from certain restrictions concerning ≠he use of gunpowder.

The Coal Mines Regulation Act applies to mines of coal, stratified ironstone, shale, and fire-clay. The Metalliferous Mines Regulation Act applies to all mines not included under the Coal Mines Act, and therefore controls not only workings for lead, tin, copper, and iron, commonly known as mines, but also the salt-mines, and underground quarries worked for stone, slate, or other earthy minerals. The principal provisions of the Coal Mines Regulation Act have been set forth at vol. vi. p. 78; those of the Metalliferous Mines Regulation Act are similar, but less strict owing to the almost complete absence of fire-damp. One important difference is that the manager of a mine under the Metalliferous Act need not hold any certificate of competency or service.

Other Acts of Parliament are the “Explosives Act, 1875” (38 Vict. c. 17), regulating the manner in which explosives are stored; the “Elementary Education Acts, 1876 and 1880” (38 & 39 Viet, c. 79, and 43 & 44 Vict. c. 23), regulating the employment of children; the “Factory and Workshop Act, 1878” (41 Vict. c. 16), which applies to the dressing floors of mines under the Metalliferous Mines Regulation Act.

The statute of Elizabeth (43 Eliz. c. 2) which was passed for raising money for the relief of the poor mentions coal mines, but omits other mines; these have been made subject to poor-rates by “The Rating Act, 1874” (37 & 38 Vict. c. 54). The “Employers’ Liability Act, 1880” (43 & 44 Vict. c. 42), extends and regulates the liability of employers to make compensation for personal injuries suffered by workmen in their service. Finally, if, as sometimes happens, works are put up at a mine for roasting copper ores with common salt in order to extract the metal by the wet way, the provisions of the “Alkali, &c., Works Regulation Act, 1881” (44 & 45 Vict. c. 37), must be attended to.

It is thus very evident that the laws affecting mines have received most important additions during the last few years.

15. Accidents in Mines.— Mining is one of the occupations that may decidedly be called hazardous. This fact has been thoroughly impressed upon the public mind by explosions of fire-damp in collieries; but, though accidents of this kind are appalling, owing to the number of victims who perish at one time, fire-damp is by no means the worst enemy with which the miner has to contend. Falls of roof and sides both in collieries and metal mines are far more fatal in their results. With the risks attending the collier’s calling we need not deal, as statistics upon this subject have been already given (see Coal, vol. vi. p. 79); but the figures below relating to metalliferous mines prove that the occupation of the metal miner is very little less dangerous. [table]

This table shows that the average accidental mortality of the persons employed underground in metalliferous mines is 2'37 per 1000. During the ten years 1873-1882 the corresponding mortality at mines under the Coal Mines Act was 2’57, showing a difference of only 0 , 20 per 1000 in favour of the metal miner; and when we take the well-known metalliferous district of Cornwall and Devon we find a death-rate for the ten years mentioned of 2 ’ 63 per 1000, which therefore exceeds that of coal mines.

Reference to the table shows that more than one-third of the deaths were caused by falls of ground. The actual percentages of the deaths are as follows:—falls of ground 35’5, in shafts 26’2, miscellaneous 25 1, on surface 13Ί. The accidents in shafts are due to falls from ladders, cages, and man-engines, ropes and chains breaking, overwinding, and other causes, whilst the miscellaneous accidents include numerous fatalities in connexion with blasting operations. The surface accidents are mostly caused by persons becoming entangled in machinery, and there have been several fatal boiler explosions.

In spite, however, of all the dangers to which miners are exposed, they are less likely to be the victims of accident than railway servants, among whom the rate of fatal accidents varies from 2’5 per 1000 on passenger traffic lines to 3 - 5 per 1000 on lines possessing a heavy goods traffic. a

Statistics concerning accidents in mines are published by many foreign countries; the most minute are those prepared by the Government mining engineers in Prussia. The average annual death-rates per 1000 persons employed below ground and above ground from accidents in mines in Prussia during the fifteen years 1867 to 1881 have been:—coal mines 2’952, lignite mines 2’474, metal mines Γ446, other mines 1’693, all the mines together 2’476. In making any comparison between these figures and those we have given for Great Britain, it is necessary to recollect that the mines under the Coal Mines Act include some workings which in Prussia would be classed as metalliferous, and that British mines under the Metalliferous Act include underground stone-quarries.

Before concluding the subject of accidents, it is necessary to point out that successful efforts have been made of late years to mitigate their results. In the first place, persons equipped with the Fleuss breathing apparatus can now enter mines after explosions, in spite of the noxious and irrespirable gases, and save lives which would otherwise be sacrificed. Secondly, by means of the instruction afforded by classes established by the St John Ambulance Association, miners are learning how best to render first aid to the injured before the arrival of a medical man, and there is no doubt that many valuable lives have been lost in times past for want of this knowledge. Thirdly, a vast amount of good has been done by the establishment of Miners’ Permanent Relief Societies in different districts, which afford aid to persons disabled by accidents and to the dependent relatives of those who have unfortunately lost their lives by any mining fatality.

16. Useful Minerals produced in Various Parts of the Globe. Great Britain and Ireland.— The mineral produce of the United Kingdom for the year 1881 is summed by Mr Robert Hunt as follows :— [table]

The total value of minerals produced in 1881 was £76,201,695, 2s., exclusive of slate, building-stone, limestone, and other stones worked by mines and quarries.

The quantity of coal raised in 1882 was 156,499,977 tons.

The metals obtained from the ores produced in the United Kingdom in 1881 were— [table]

The total value of minerals and metals obtained from the mines and other mineral workings of the United Kingdom in 1881 was— [table]

From these tables it is evident that coal and iron are by far the most important mineral productions of the United Kingdom, as 94 per cent, of the total value is due to these two substances.

France.— The mineral productions of France for the year 1880 are set forth in the following table:— [table]

The quantities of metal produced in France from native and foreign ores in 1880 were— [table]

Germany. —The mining industry of the German empire is of high importance. The output of the mines in 1881 is shown by the following table,—taken from the Stat. Jahrb. für das Deutsche Reich, Berlin, 1883, p. 27. The production of common salt, potassium chloride, and other salts from brine is also considerable. The total quantity for the German empire in 1881 was 693,000 metric tons, worth 33,567,000 marks, including 113,200 tons of potassium chloride valued at 14,090,000 marks. [table]

Austria-Hungary.— Among the famous mines of the Austria-Hungarian empire may be mentioned those of Hungary and Transylvania for gold and silver; Styria produces much of the iron; quicksilver is yielded by the mines of Idria in Carniola, lead and silver by those of Przibram in Bohemia; salt is obtained in the Austrian Alps and in Galicia, which also produces petroleum and ozokerite.

The production of minerals and metals in Austria during the year 1881 was as follows :— [table]

Exclusive of salt, the value of the produce of the Austrian mines in 1881 was 44,693,692 florins. The total output of salt in 1881 was 267,279 metric tons, valued according to the monopoly prices at 23,000,498 florins. [table]

Belgium.— Belgium is rich in coal, the output in 1881 being no less than 16,873,951 metric tons, valued at 163,704,242 francs. Though it produces iron ores, it is largely dependent upon other countries, and especially the grand-duchy of Luxemburg, for supplies for its blast furnaces. The principal lead mine is that of Bleiberg, and the calamine deposits in the neutral territory of Moresnet have long been worked with success by the celebrated Vieille Montagne Company, which also owns zinc mines in Belgium, Germany, Sweden, Sardinia, and Algeria.

Russia. —In a vast empire like Russia it is not surprising that there should be valuable deposits of a great variety of minerals. Among the most important are the auriferous alluvia of the Ural mountains and Siberia, which in 1880 yielded 115,940 troy K> of gold, worth more than 5 millions sterling. Platinum is found associated with the gold-bearing sands of the Urals; the output in 1880 was 7895 troy lb. Zinc ore is largely worked in Poland. Import ant supplies of chromic iron ore are derived from the Urals, amounting in 1880 to more than 8000 tons. The metallic copper produced in 1880 was about 3100 tons, and the oil wells of Baku yielded in that year 346,000 tons of petroleum. Russia also possesses mines of iron ore, manganese, lead, silver, coal, and lignite. A little tin ore is furnished by Finland.

Italy.— The most important mineral in Italy is sulphur, 359,540 tons (metric), worth 36,448,453 lire, having been obtained in 1880, and mainly from seams containing the native element in the Miocene rocks of Sicily and Romagna.

The celebrated iron mines of the island of Elba have been worked from very early times, and furnish a valuable ore; and the deposits of calamine, lead ore, and silver ore in Sardinia form no small proportion of the mineral wealth of the Italian kingdom. The gold mines in and near the Vai Anzasca (Piedmont) are producing more than 7000 ounces of metal yearly.

Spain.— Spain is justly celebrated for its mineral wealth. It produces more cupreous pyrites than any other country in the world, and very large amounts of lead ore and quicksilver; and its iron ores are abundant and of excellent quality. The principal lead mines are in the provinces of Jaen (Andalusia) and Murcia, and the total amount of metallic lead produced in Spain or from Spanish ores is estimated to be 120,000 tons yearly.

Cinnabar, the heavy red ore of mercury, naturally attracted attention at a very early date, and the world-renowned Almaden mine has been worked from time immemorial. The output in 1880 was 1387⅛ tons (metric) of quicksilver.

The cupreous pyrites, often known as sulphur ore, is obtained from the province of Huelva, where vast deposits occur over a belt of country nearly 100 miles long by 20 miles wide. The Rio Tinto mines are the largest in the district, and are worked on a gigantic scale. The company employs upwards of 10,000 hands, or more persons than are engaged in all the Cleveland iron mines, and the output is upwards of a million tons per annum. About one-quarter of this, containing 3∣ per cent, of copper, is exported, mainly for the manufacture of sulphuric acid and subsequent treatment for copper and silver, whilst theremaining three-quarters, with 2⅜ to 2⅜ per cent, of copper, are treated on the spot. The ore contains rather less than 1 oz. of silver to the ton, and a few grains of gold. These are profitably extracted from the burnt ore by Claudet’s process, and some idea of the importance of the copper and silver will be gained by reference to the following figures. During the year 1881 there were obtained from cupreous pyrites imported into the United Kingdom in 1881, mainly from Spain and Portugal, 14,000 tons of copper, 258,463 oz. of silver, and 1490 oz. of gold. The total value of the silver and gold was £64,195.

The total output of iron ore in 1880 was 3,565,338 metric, tons, more than two-thirds, viz., 2,683,627 tons, being obtained from the celebrated mines near Bilbao in the province of Biscay. England, France, Belgium, and Germany are all glad to draw supplies of excellent red and brown haematite from the Bilbao mines. Murcia comes next in importance to Biscay, with a production of 539,328 tons.

Portugal.— The great mineral belt of Huelva extends into Portugal, and deposits of cupreous pyrites almost identical with that of Rio Tinto have been wrought from very early ages. The principal mine, San Domingos, is close to the Spanish frontier. It is estimated that the workings had yielded up to the year 1877 no less than 3,578,745 English tons of cupreous pyrites, by far the greater part of this having been extracted in recent times. The quantity of ore raised from the mine in 1882 was 405,029 tons.

Portugal possesses notable manganese mines, but produces comparatively small quantities of iron, lead, and copper.

Norway.— The mines at Kongsberg are famous for the large quantities of native silver they produce, and enormous masses are sometimes met with. The annual output is from 10,000 to 12,000 troy ounces. Copper ore and cupreous pyrites are also mined in Norway, and there are important workings for nickel and cobalt and for apatite. Alluvial gravels have been washed for gold in Norwegian Finland.

Sweden.— The most important mineral obtained in Sweden is iron ore, much being in the form of magnetite; red haematite also is mined, and brown haematite is dredged up from some of the lakes. The principal iron-producing districts are those of Norberg, Dannemora, Nora, and Perseberg. The output of the Swedish mines in 1880 was— [table]

Greece.— One of the most interesting undertakings of modem times has been the re-working of the Laurium mines, which are situated in the southern extremity of Attica; and an account of them written by Cordelia furnishes many curious details concerning the methods of mining, washing, and smelting employed by the ancients. The workings for lead and silver appear to have been carried on with the greatest vigour between 600 B. c. and the Peloponnesian War, and were finally abandoned in the 1st century of the Christian era. Huge piles of slag which had accumulated from the old smelting works were found to be well worth being re-worked for silver and lead, and operations were commenced in 1864. Five years later the old heaps of mine refuse began to be treated, and at last in 1875 a French company resumed working the mine. A Greek company employing some 3000 persons is now producing annually from the old mine heaps no less than 8000 to 9000 tons of pig lead, yielding 45 oz. of silver to the ton, whilst the mines of the Compagnie française des mines du Laurium made an output in 1881 of 36,664 tons (metric) of roasted calamine, with 40 to 60 per cent, of zinc, in addition to lead ore and mixed ores. Cordelia calculates that during the three hundred years the Laurium mines were worked by the ancients the total amount of lead produced was 2,100,000 tons, with 22⅜ million troy tt>of silver. Besides this the ancients left behind two million tons of lead slags containing on an average 10 67 per cent, of lead, 109 million tons of mine refuse with 1 ⅛ to 18 per cent, of lead, and excavations to the extent of 51 million cubic yards with lead ore still in sight. They did not touch the calamine deposits. Next in importance to lead, silver, and zinc comes bay-salt, and after that emery. The island of Naxos furnished 3300 metric tons of emery in 1877, valued at £28,000.

Africa.— Algeria is rich in iron, and three-fourths of the value of its total mineral output are due to ores of this metal. In 1880 the iron mines produced 614,000 metric tons of ore, Mokta-el-hadid mine, near Bona, alone yielding about 300,000 tons. Algeria also possesses mines of copper, lead, zinc, and antimony.

The name * ’ Gold Coast” applied to part of the shores of Africa, denotes its productiveness of the precious metal, and it is probable that very important supplies of gold will one day be derived from various districts of the Dark Continent.

Cape Colony possesses rich copper mines in the Namaqualand division, which in 1882 produced ore and metal worth £331,546; however, the most valuable and remarkable mineral deposits of Africa at the present time are the diamond mines. The first diamonds were obtained from recent gravel in the bed of the Vaal river, and it was afterwards discovered that the precious stones could be obtained from the so-called dry diggings. The most important of these, the Colesberg Kopje, now known as the Kimberley mine, produced in 1881 diamonds weighing 900,000 carats, worth £1,575,000. Three other neighbouring mines are Old De Beer’s, which yielded 300,000 carats in 1881, worth £600,000, Du Toit’s Pan, and Bulfontein. The value of the diamonds raised in South Africa since 1870 amounts to forty millions sterling; indeed the Kimberley mine alone was estimated in 1877 to have already produced ten million pounds worth of diamonds, extracted from 4 million tons of diamantiferous rock.

Asia.— For many centuries India was regarded as possessing fabulous mineral wealth, and a strong basis for this idea may be found in the existence of traces of mining on a very extensive scale. No doubt in early days India did supply what then appeared to be very large quantities of metals, and a country that produces gold and precious stones is apt to be endowed by the popular mind with boundless riches. The actual amounts of mineral raised in India at the present day are comparatively small. Gold exists over considerable areas, but it remains to be proved that the gold mines of the Wynaad and Mysore can be profitably worked by British companies. Diamonds occur and are worked in alluvial diggings and in a conglomerate belonging to the Vindhyan formation. Sapphires and rubies are obtained from Upper Burmah. Ceylon produced in 1880 no less than 10,286 tons of graphite or plumbago, valued at £192,879. Petroleum is abundant in Upper Burmah, and oil from wells has been utilized for upwards of twenty centuries. The total output in 1873 was estimated to be about 10,000 tons yearly. Tin ore occurs and is worked in Tenasserim. Passing into Siam and the Malay Peninsula we find deposits of alluvial tin ore, producing what is known in commerce as Straits tin. A little to the east are the islands of Banca and Billiton, which for many years have been a source of wealth to the Dutch Government. The sales of Banca tin in 1881 amounted to 4339 tons, and those of Billiton tin to 4735 tons, whilst 11,475 tons of Straits tin were exported from Penang and Singapore. Stanniferous alluvia are also worked in Karimon, Singkep, and Sumatra, whilst the latter island possesses also valuable seams of coal.

Borneo furnishes coal, antimony ore, and some cinnabar; and river-gravels are washed for diamonds, gold, and platinum.

There is no doubt that the mineral wealth of China is enormous. In addition to important coal-fields it possesses numerous metallic mines. The province of Yunnan in the south of the empire seems to be specially favoured with regard to metalliferous wealth, for mines of gold, silver, copper, lead, tin, and iron are worked there, whilst jade and precious stones are found in the beds of rivers.

Japan produces more than 3000 tons of copper yearly, or about as much as the British Isles. The output of lead and tin is insignifi cant, but the quantity of silver, exceeding 300,000 oz. yearly, is worthy of notice. Gold, iron, and petroleum are other products of Japan.

The gold of Siberia has been mentioned in speaking of Russia.

Canada.— The Dominion of Canada is rich in minerals. Gold-bearing quartz veins are worked in Nova Scotia, whilst in British Columbia alluvial deposits are the main source of the supply. Silver occurs on Lake Superior, the most important mine being that of Silver Islet, which from 1869 to the spring of 1877 yielded 2⅛ million ounces of silver, and gave a profit of £200,000.

Rocks resembling the copper-bearing strata of the United States territory are mined in Michipoten island in Lake Superior. Iron ores, in the form of magnetite, red haematite, limonite, and ilmenite, are worked in various parts of Canada.

Petroleum is derived from oil wells in Western Ontario, and the quantity refined in 1875 was about 210,000 barrels, each of 40 gallons. It is in Ontario also that the veins of apatite exist from which a large amount of that useful mineral has been raised.

United States.— The mineral wealth of the United States is admirably summed up by Mr Richard P. Rothwell in his address to the American Institute of Mining Engineers. [table]

“The statistics of other useful minerals and metals show an equally marvellous advance during the past thirty years. The production of pig iron, which in 1852 was 541,000 net tons, in 1861 was 653,000 tons, and in 1871 was 1,708,000 tons. Ten years later, in 1881, we produced no less than 4,144,000 tons, an increase in thirty years of nearly 800 per cent.

“Lead, which appears at 14,400 tons in 1852, varied but little from that figure until the construction of railroads into the argentiferous lead-mining districts of the west about 1870. Eureka, Nevada, Utah, and more recently Colorado, with its Leadville bonanzas, rapidly raised the production from 18,000 tons in 1871 to 47,000 tons in 1873, 75,000 tons in 1877, and 105.000 tons in 1881.

"Our production of copper steadily increased from 1000 tons in 1852 to 31,000 tons in 1881,—the enormous output of that unrivalled mine Calumet and Hecla steadying the production and neutralizing the fluctuations of the lesser mines.

“Quicksilver has shown wide fluctuations, due more to trade combinations than to the condition of the mines. In 1852 the output amounted to 20,000 flasks; but it went as low as 10,000 flasks in 18β0, and rose to 53,000 flasks five years later; from this it declined to 15,000 flasks in 1875, though in the following year it grew to 75,000 flasks. Last year we produced 59,000 flasks. “Gold is the only metal in which our production has been declining. In 1852 it amounted to $60,000,000; but, with some fluctuations, it lias now declined to less than $32,000,000 annually. “The production of silver, on the contrary, has largely increased. Commencing in 1859 with $100,000, it has now attained $45,000,000. In 1877 only were these figures exceeded, and then only by about $1,000,000. “The production of petroleum, that great American industry, has grown with wonderful rapidity. In 1859 it commenced with only 3000 barrels, and, after an almost uniform increase, it attained last year the enormous figures of 27,000,000 barrels. Scientific investigation has recently raised a note of warning in this industry, asserting the limited area of oil-producing territory and its approaching exhaustion.”

Some valuable statistics concerning the production of the precious metals in the United States are contained in a report issued by the Census Bureau. The output for the year ended 31st May 1880 is summed up as follows :— [table]

The State producing the greatest value is Colorado, viz., $19,249,172, or gold 130,607 oz. and silver 12,800,119 oz.; California comes next, having produced $18,301,828 of bullion, and then Nevada, with $17,318,909 of bullion.

The greatest gold producer among the States and Territories is California, with 829,676 oz. of gold, half from deep mines and half from placers. Next follows Nevada, with 236,468 oz. of gold, of which only about 1 per cent, came from placer mines; then Dakota, 159,920 oz. of gold, nearly entirely produced by deep mines; and in the fourth rank Colorado, 130,607 oz., with a placer production of less than 5000 oz.

The greatest silver producer is Colorado, with 12,800,119 oz.; then Nevada, 9,614,561 oz.; then Utah, 3,668,365 oz.; Montana, 2,246,938 oz.; and fifthly Arizona, 1,798,920 oz.

It is useless within the limits of this article to attempt to convey an adequate idea of the enormous mineral resources of the United States. We can merely very briefly allude to some of the principal deposits, which are of commercial value on account of their magnitude, of scientific interest owing to their mode of occurrence, and of technical importance as having led to the introduction of considerable improvements in the arts of mining, milling, and dressing.

Among these may be mentioned the coal and anthracite mines and oil wells of Pennsylvania, the gold and quicksilver mines of California, the silver mines of Nevada, the lead and silver mines of Colorado, and the copper mines of Lake Superior. The articles Coal (vol. vi. p. 60) and Gold (vol. x. p. 743) may be referred to for information concerning the occurrence of these minerals and the method of extracting gold by hydraulic mining and improved stamping machinery.

Quicksilver in the form of native mercury and cinnabar occurs in considerable abundance in California, and much of it is found in connexion with serpentine, either in the serpentine itself or in sandstone near its junction with serpentine. The most important mines are those of New Almaden in the southern part of the State near San Jose. The deposit at Sulphur Bank in Lake County is of much geological interest. It consists of native sulphur, gypsum, and cinnabar in a decomposed andesitic lava close to an extinct geyser from which boiling water still issues. The top of the bank was worked open-cast for sulphur, and then for sulphur and cinnabar, and now underground mining is carried on in stratified sandstone and shale impregnated with cinnabar and underlying the lava.

Some of the most marvellous silver mines in the world are those upon the Comstock lode in Nevada. A horizontal section of part of this great vein is shown on Plate IV., copied from the excellent and well-known report of Mr J. D. Hague. The strike is nearly north and south, and the dip about 43° to the east. “The vein matter of the Comstock consists of crushed and decomposed country rock, clay, and quartz.” “Up to January 1, 1880, the Comstock had yielded in twenty years about $325,000,000 worth of bullion. The total length of shafts and galleries is about 250 miles. The number of men employed in the mines in January 1880 was 2800, earning average wages of $4 a day. At the same date 340 men were at work in the amalgamating mills.” The heat of the Comstock lode is remarkable. On the 2700 feet level of the Yellow Jacket mine Mr Becker found the temperature of the water to be 153°, that of the air 126°; whilst the water in the Yellow Jacket shaft at a depth of 3065 feet has a temperature of 170° Fahr.

During the last few years the Comstock lode has been falling off in productiveness. In 1876 the total yield of the Comstock lode was $38,572,984 (gold, $18,002,906; silver, $20,570,078). During the census year ending May 31, 1880, the product of the whole Comstock district, including outlying veins, was $6,922,330 (gold, $3,109,156; silver, $3,813,174), showing a decline of $31,650,654, or 82'06 per cent., since 1876.

Though the extraction of silver from its ores may be regarded as the business of the metallurgist rather than of the miner, we must not forget to mention that it is to the necessities of the treatment of the Nevada ores that we owe the system of pan amalgamation first developed in that State and practised since in Colorado.

Another district in Nevada which cannot be passed over in silence is that which contains the Eureka and Richmond mines, which are celebrated, not only for the silver they have produced, but also for the important trial in which the issue hinged upon the definition of the term vein or lode (p. 441). The bullion produced in the Eureka district from ore raised and treated during the census year ended May 31, 1880, was—gold, 62,893 oz.; and silver, 2,037,666 oz.; worth altogether $3,934,621. ®

The history of Leadville in Colorado seems like a romance when we read of the rapid development of the mines, the creation of a large and important town, the erection of smelting works and the building of railways, under very adverse conditions, in the heart of the Rocky Mountains, all within the space of four or five years. It affords additional proof that the miner is the true pioneer of civilization. The main facts concerning the Leadville deposits are admirably summed up by Mr S. F. Emmons, from whose report we borrow, not only the following facts, but also the geological section across the district (Plate IV. ).

The principal deposits of the region are found at or near the junction of the porphyry with the Blue limestone, which is the lowest member of the Carboniferous formation. This bed is about 150 or 200 feet thick, and consists of dark blue dolomitic limestone. At the top there are concretions of black chert. The porphyry occurs in intrusive sheets which generally follow the bedding, and almost invariably a white porphyry is found overlying the Blue limestone. This porphyry is of Secondary age; it is a white homogeneous-looking rock, composed of quartz and felspar of even granular texture, in which the porphyritic ingredients, which are accidental rather than essential, are small rectangular crystals of white felspar, occasional double pyramids of quartz, and fresh hexagonal plates of biotite or black mica. Along the plane of contact with the porphyry the limestone has been transformed, by a process of gradual replacement, into a vein consisting of argentiferous galena, cerussite, and cerargyrite mixed with the hydrous oxides of iron and manganese, chert, granular cavernous quartz, clay, heavy spar, and ’ ‘ Chinese talc,” a silicate and sulphate of alumina. The vein seems to have been formed by aqueous solutions, which took up their contents from the neighbouring eruptive rocks and brought about the alteration of the limestone as they percolated downwards through it. In Carbonate Hill, a gradual passage may be observed from dolomite into earthy oxides of iron and manganese. The masses of workable ore are extremely irregular in shape, size, and distribution. They are often 30 to 40 feet thick vertically, and occasionally 80 feet, but only over a small area. The rich ore bodies are commonest in the upper part of the ore-bearing stratum. At Fryer Hill the Blue limestone is almost entirely replaced by vein material.

In the census year ended May 31, 1880, Lake County, Colorado, which includes the Leadville district, produced 28,226 gross tons of lead, with 3830 oz. of gold and 8,853,946 oz. of silver, of a total value of $13,032,464. «

The most important copper mines of the United States are those on Lake Superior, where the native metal occurs “in veins, in large masses, or scattered more or less uniformly in certain beds which are either amygdaloid or conglomerates.”

The copper-producing districts are those of Ontonagon, Keweenaw County, and Portage Lake. The last-named contains the famous Calumet and Hecla mine, which alone produced 15,837 tons of copper in 1880, or about half the entire output of the United States. The deposit from whence this vast amount of copper was obtained is a bed of conglomerate, generally called a vein, dipping about 38° northwest. It has been worked for a depth of 2250 feet on the incline. In 1875 the stuff stamped yielded 4⅛ per cent, of copper.

In conclusion, we will point out that the value of the mining industry in the United States exceeds that of any other country in the world, Mr Porter estimating it for 1879-1880 at 360 million dollars, and that of Great Britain at 325 millions. Germany holds the third rank, followed by France and Russia. The United States produce 33 per cent. of the gold yield of the whole world, 50 per cent, of the silver, 22 per cent, of the pig iron, ® 29 per cent, of the steel, and about 25 per cent, of the lead.

Mexico has been renowned for its gold and silver mines ever since rhe Spaniards first took possession of it, and its production is still very considerable. Indeed, after the United States, it still produces far more silver than any other country in the world. The average annual output of silver during the twenty-five years 1851 to 1875 is estimated by Dr Adolf Soetbeer at 501,520 kilogrammes, or 16,124,235 oz.; whilst the average annual output of gold during the same period was 1785 kilogrammes, or 57,389 oz. Tin ore occurs in considerable quantities in Mexico, and is likely to be worked on a large scale as soon as the tin district is opened up by a railway.

Central America possesses numerous gold mines.

South America.— Venezuela produces gold, copper, and a little lead. The copper is found at Aroa near the north coast, and the gold in the province of Guiana, which is now producing upwards of 100,000 oz. annually. It is highly probable that the existence of this gold was known to the Indians, who reported it to Sir Walter Raleigh, and so led him to undertake his unfortunate expedition in search of “El Dorado.” French Guiana contains workable deposits of gold, and yielded 72,168 oz. in 1880.

The chain of the Andes forms a long belt of mineral-producing country. Beginning with the United States of Colombia we have a country rich in gold,—the State of Antiquoia being especially favoured in this respect. The annual yield of all the states is about 200,000 oz. Colombia has mines of rock salt, yielding 19,000 tons a year, and the emerald mine at Muzo has long been famous. Peru is renowned for its silver mines; the best-known are those of Cerro de Pasco, situated at an elevation of 14,000 feet above the sea-level. Passing into Bolivia, we must notice the silver mines of Potosi, the wealth of which is proverbial. Chili is best known as the principal copper-producing country of South America; but its silver mines are not unimportant, and beds of nitrate of soda are largely wrought.

The most remarkable gold mines of Brazil lie in the province of Minas Geraes, whilst diamonds are obtained in that of Matto Grosso. In the Argentine Republic gold, silver, and copper mines are worked, especially in the provinces on the eastern flanks of the Andes.

The total annual output of the precious metal in South America is estimated to be upwards of 300,000 oz. of gold, and 2,000,000 oz. of silver. In 1877 Chili exported 35,128 metric tons of metallic copper, in addition to ore and regulus.

Australia.— Australia is remarkably rich in minerals, especially gold (see Gold, vol. x. p. 744), tin, and copper, and its coal deposits are likely to be largely utilized in the future.

Queensland, though a young colony, has already made itself famous for gold and tin, and it also possesses vast resources of coal and copper, in addition to the ores of other metals. The quantity of gold sent by escort from the different gold fields was 204,388 oz. in 1880, in addition to what was carried by private hands. Tin ore was first worked in 1872 near the border of the colony with New South Wales, and large quantities of stream tin have been obtained from very shallow alluvial diggings near Stanthorpe. Like gold, the tin ore is not confined to one district; it occurs and is worked at the North Palmer diggings; a little to the south is Great Western, rich in tin ore, and so is Herberton to the north-east on the other side of the Dividing range.

In 1881 New South Wales produced minerals and metals worth £2,373,191, viz., 149,627 oz. of gold, 1,775,224 tons of coal, 8200 tons of tin, 5493 tons of copper, 6560 tons of iron, besides silver, oil-shale, and antimony. In addition to the facts concerning the occurrence of gold already mentioned {loc. cit.), it is interesting to note that auriferous conglomerates containing the precious metal in payable quantities have been discovered and worked in this colony in rocks of the age of the Coal Measures. ® The most important tin district is that of Vegetable Creek in New England, which from 1872 to 1880 produced 20,988 tons of tin ore. The accompanying map (fig. 105 β ) shows the recent alluvium which has hitherto been the main source of the supply, and the deep leads which, as far as explored at present, promise still greater riches. The section (fig. 106 β ) shows that these deep leads, like those of the gold fields (Gold, vol. x. p. 743), are old alluvia preserved under a capping of basaltic lava. There are also numerous tin lodes which are beginning to be worked.

Victoria heads the list of gold-producing British colonies, having yielded in 1882 as much as 864,610 oz., of which 352,078 oz. were derived from alluvial deposits, and 512,532 oz. from quartz mines. 1077 tons of tin ore were raised and 375 tons of antimony ore.

South Australia is the great copper-producing province, though the yield is not so great as it was ten years ago. The principal mines now at work are on Yorke’s Peninsula. In 1881 South Australia produced 3824 tons of copper, worth £263,370, and 21,638 tons of copper ore, worth £154,926.

In 1881 Western Australia exported 1400 tons of lead ore, valued at £11,204.

Tasmania, like some parts of Australia, is rich in tin ore, which is now obtained principally from an alluvial deposit at Mount Bischoff. The ore is now almost entirely smelted in the colony, and in 1880 the exports were 3951 tons of metal and 3 tons of ore, worth altogether £341,736.

New Zealand furnishes a considerable amount of gold from quartz reefs and alluvial diggings. The annual exports during the ten years 1862 to 1872 were often 600,000 and even 700,000 oz. Of late years the yield has gradually diminished, and in 1880 only 303,215 oz., valued at £1,220,263, were exported. Silver is exported to the extent of 20,000 to 30,000 oz. annually; it is mainly derived from the gold obtained in the Thames district, which contains about 30 per cent, of the less valuable metal. Coal is worked in several places, but the total output is at present comparatively small.

New Caledonia. — The discovery of nickel ore in this island by Μ. Garnier in 1867 was one of great mineralogical interest, and it has since borne fruits of considerable commercial importance. The New Caledonia ores are hydrous silicates of nickel and magnesium, which occur in veins in serpentine, and contain from 7 to 18 per cent, of metal. The mineral is found on the Mont d’Or not far from Noumea. Most of the ore is sent to France to be treated.

To the list of works on mining mentioned in the article Coal (vol. vl p. 81> the following may be added :—Callon, Court d'exploitation des Mines, Paris, 1874, and English translation by C. Le Neve Foster and W. Galloway; Serio, Leitfaden tur Bergbaukunde, Berlin, 1878; Zoppetti, Arte mineraria, Milan, 1882; A. von Groddeck, Die Lehre von den Lagerstätten der Erze, Leipsic, 1879; P. von Rittinger, Lehrbuch der Auf bereitungskunde, Berlin, 1867; Jahrbuch für das Berg-und Hüttenwesen im Königreiche Sachsen, Freiberg, annually; Annual Reports of Η. Μ. Inspectori of Mines-, Preliminary Report of Her Majesty’s Commissioners Appointed to Inquire into Accidents in Mines, London, 1881; Annales des Mines, Paris, 6 parts published yearly; The Engineering and Mining Journal, New York, published weekly; Transactions of the American Institute of Mining Engineers, Philadelphia; Die berg-und hüttenmännische Zeitung, Leipsic, weekly; Oesterreichischβ Zeitschrift für Berg-und Hüttenwesen, Vienna, weekly. (C. I.. N. F.)