In the mutual transformations of water and ice, many remarkable physical phenomena occur. Thus, during the process of melting a block of ice or of freezing a quantity of water, no change of temperature can take place so long as there is a thorough mixture of water and ice. Consequently, the “freezing-point” or temperature at which water freezes is a temperature so readily determined that it is conveniently employed as one of the standard temperatures in the graduation of ordinary thermometer scales, such as the centigrade, the Fahrenheit, and the Réaumur. The centigrade scale, whose zero corresponds to this freezing-point of water, is the temperature scale that is employed throughout this article. In the act of freezing, water, though its temperature remains unchanged, undergoes a remarkable expansion or increase of bulk, so that ice at 0° C. is less dense than water—a fact demonstrated at once by its power of floating. “Ground-ice” or “anchor-ice,” which forms in certain circumstances at the bottom of streams, is only an apparent exception to this relation between the densities of water in its solid and liquid states, being retained there by the cohesion between it and the stones or rocks which compose the river’s bed. When forcibly released from this contact with the bottom, the ice at once ascends to the surface. Ground-ice may thus be the lowest stratum of the once completely frozen mass of water, adhering to the bottom during the thawing and melting of the ice at the surface; or it may even be formed under favourable conditions below briskly flowing water, probably by the action of eddies, which draw the surface water down through the warmer but denser liquid, and thus cool the stones and rocks at the bottom. As water then expands on freezing, so conversely ice contracts on melting; and the ice-cold water thus formed continues to contract when heated until it has reached its point of maximum density. Joule, from a series of careful experiments, determined the temperature at which water attains its maximum density to be 39 o, l Fahr., or very nearly 4° C. Hence water contracts as its temperature rises from 0° C. to 4° C.; but at higher temperatures it behaves like the great majority of other substances, expanding with rise of temperature. At no temperature, however, does water in the liquid state become less dense than ice, as the following table of relative densities shows :— [table]

Under the influence of heat, ice itself behaves as most solids do, contracting when cooled, expanding when heated.

According to Pliicker, the coefficient of cubical dilatation at moderately low temperatures is Ό001585. From a series of elaborate experiments, Person deduced ‘505 as the specific heat of ice, or about half that of water; in other words, the heat required to raise 1 lb of water 1° C. will raise 2 ft) of ice through the same range of temperature or 1 ft> of ice through 2° C.

Though no rise of temperature accompanies the melting of ice, there is yet a definite quantity of heat absorbed, and a corresponding amount of work done—mainly in altering the physical condition of the substance. The heat which disappears is transformed into other and less evident forms of energy,—as, for example, the energy of translatory motion, which is the chief characteristic, according to the recognized molecular theory of matter, of the molecule in the liquid as compared with the molecule in the solid. The heat which is thus absorbed during the melting of unit mass of ice is called the latent heat of water, and its value in ordinary heat-units is 79 ’ 25, according to the determination of Person. Hence as much heat is required to transform 1 ft) of ice at 0° C. into water at the same temperature as would raise in temperature 1 ft> of water through a range of 79 0, 25 C., or 79 ’ 25 ft) of water through a range of 1° C. The same amount of heat which is absorbed when ice becomes water is evolved when water becomes ice, so that the melting of ice is accompanied by the abstraction of heat from surrounding objects, that is, by a cooling effect; and the freezing of water by a heating effect. These thermal effects are generally masked by the processes whereby the change of state is effected; but the cooling which accompanies the melting of ice may be observed when pressure is used as the agent for accomplishing the change. That ice can be so melted by increase of pressure was first pointed out by Professor James Thomson (now of Glasgow) in a paper published in the Transactions of the Royal Society of Edinburgh for 1849; previous to that time the temperature of melting ice was believed to be absolutely constant under all conditions. Thomson showed that, since water expands on freezing, the laws of thermodynamics require that its freezing-point must be lowered by increase of pressure; and, by an application of Carnot’s principle, he calculated that for every additional atmosphere of pressure the freezing-point of water was lowered by Ό075 of a degree centigrade. This remarkable result was soon after verified, even to its numerical details, by his brother, Sir William Thomson {Proceedings of the Royal Society of Edinburgh, 1850). The Thomsons and Helmholtz have since then successfully applied this behaviour of ice under pressure to the explanation of many curious properties of the substance. When two blocks of ice at 0° C. are pressed together or even simply laid in contact, they gradually unite along their touching surfaces till they form one block. This regelation, as it is called, is due to the increased pressure at the various points of contact causing the ice there to melt and cool. The water so formed tends to escape, thus relieving the pressure for an instant, refreezing, and returning to the original temperature. This succession of melting and freezing, with their accompanying thermal effects, goes on until the two blocks are cemented into one. Thus it is that a snowball is formed; and in virtue of the same succession of phenomena does the glacier mould itself to its rocky bed and flow down the valley, behaving in many respects like a viscous fluid.

Ice forms over fresh water if the temperature of the air has been for a sufficient time at or below the freezing-point; but not until the whole mass of water has been cooled down to its point of maximum density, so that the subsequent cooling of the surface can give rise to no convection currents, is the freezing possible. Sea-water, in the most favourable circumstances, does not freeze till its temperature is reduced to about - 2° C.; and the ice, when formed, is found to have rejected four-fifths of the salt which was originally present. In the upper provinces of India, water is made to freeze during cold clear nights by leaving it overnight in porous vessels, or in bottles which are enwrapped in moistened cloth. The water then freezes in virtue of the cold produced by its own evaporation or by the drying of the moistened wrapper. In Bengal the natives resort to a still more elaborate forcing of the conditions. Shallow pits are dug about 2 feet deep and filled three-quarters full with dry straw, on which are set flat porous pans containing the water to be frozen. Exposed overnight to a cool dry gentle wind from the north-west, the water evaporates at the expense of its own heat, and the consequent cooling takes place with sufficient rapidity to overbalance the slow influx of heat from above through the cooled dense air or from below through the badly conducting straw.

The growing demand for ice for domestic, medicinal, and other purposes has led, not only to the development of a regularly organized ice trade, but also to the invention of machines for the manufacture of ice in countries which do not possess a sufficient home supply. The various types of machines which have been or are in use call for a brief description. Freezing-mixtures, such as the familiar snow and salt or the mixture of sulphate or phosphate of sodium and dilute nitric acid, may be dismissed w ith a word, since they are restricted in use to the production of intense cold for a brief period of time, and are incapable of economic application to the formation of large quantities of ice.

All ice-machines which have proved of practical utility may be grouped under two great classes :—those which utilize the lowering of temperature that accompanies the rapid expansion of a compressed gas, and those which make use of the like thermal effect that results from the volatilization of some liquid. In machines of the first type, the gas usually employed is atmospheric air, which is first compressed to three or four atmospheres, and kept cool by circulating water or by other suitable means. It is then allowed to expand, and the heat necessarily absorbed during the expansion is drawn either from the water to be frozen or from a solution of brine which does not freeze at the ordinary freezing temperature, and thus becomes, so to speak, a vehicle for the cold. In 1849 Gorrie constructed such a machine, which, however, was unsatisfactory in its action, probably because the compressed air was not sufficiently cooled and dried. More efficient in their action were Kirk’s machine (patented in 1863), and Windhausen’s (1870), one of which at the Vienna exhibition produced 30 cwts. of ice per hour, at the cost of Is. per cwt. The mode of action of Windhausen’s is as follows. A piston works to and fro in a cylinder, compressing the air in the one end and allowing it to expand in the other. The compressed and therefore heated air forces its way through a valve to the cooling chambers, from which it is led towards the other end of the cylinder. Here the inlet valve is so arranged that it closes at a certain position of the receding piston, thus permitting what air has entered to expand and cool. At the return stroke this cooled air is forced out through easily opening valves,—part going to cool the chambers into which the heated compressed air enters from the cylinder, and part passing to the refrigerator, from which after serving its purpose it is pushed on by the fresh supply of cooled air to the compressing end of the piston chamber. Such machines, to work economically, require large cylinders, tight-fitting pistons working with little friction, and perfect regulation in the motions of the various parts—conditions so difficult to fulfil that refrigeration by means of compressed air may be regarded as a practical failure. The machines constructed by the Bell-Coleman Mechanical Refrigeration Company (Glasgow) utilize as the cooling agent a mixture of certain hydrocarbon gases which are obtained from the distillation of carbonaceous shale. The gas is compressed to a pressure of about 8 atmospheres, and, after being cooled by expansion, is carried off and consumed as fuel. These machines are not specially intended for the production of ice; but, as refrigerators, they are successfully employed for preserving meat on board ship.

Among machines of the second group there is a great variety of construction, because of the great differences which exist in the properties of the liquids used. Thus water, sulphuric ether, bisulphide of carbon, ammonia, methylic ether, sulphurous acid, and other substances have been employed as refrigerating agents. In all cases, it is the so-called latent heat of vaporization that is utilized; and did the efficiency of the method depend only on this, water would undoubtedly be the best material on account of the great latent heat of its vapour. But as important from a practical point of view are the vapour pressures that come into play throughout the range of temperature employed. Thus at 10° C. the pressure of water vapour is so small, only Ό12 of an atmosphere (and at lower temperatures of course it is still smaller), that, to make the evaporation of water an efficient means of refrigeration, the process must be conducted under a very much diminished pressure. As early as 1755, Dr Cullen managed to freeze water by its own evaporation in a vacuum; but this method, though greatly developed by Nairne, Leslie, and Vallance, can be applied to the production of ice in small quantities only.

The same objection applies, of course, to sulphuric ether, bisulphide of carbon, or any substance which boils under ordinary atmospheric pressure at a temperature above that of the air. Ether boils at 34 0, 8 C., and bisulphide of carbon at 46 o, 2 C.; and their vapour pressures at 10° C. are respectively ‘377 and *267 of an atmosphere. They thus volatilize much more readily than water, and require a comparatively slight vacuum to render their evaporation sufficiently rapid for refrigerating purposes. In the ether machine, which may be taken as a type, the ether, on being vaporized in the refrigerator under a partial vacuum, is drawn over and compressed to the liquid state in the condenser, which is kept cool by circulating water. From the condenser it is then led back to the refrigerator, to be re-evaporated. Perkins’s machine (1834), Twinings patent of 1850, Harrison’s machine (1857), Siebe’s machine (1862), and Siddeley and Mackay’s apparatus are ether-machines; and all except the first, which is hardly adapted for extensive freezing, surround the refrigerator with brine, which when cooled flows easily around and between the cases containing the water to be frozen. Van der Weyde (1869) substituted naphtha, gasolin, or chimogene for the ether; and in Johnston and Whitelaw’s machine bisulphide of carbon is used somewhat similarly. The great difficulty in machines of the ether type is to prevent leakage, so as to keep the partial vacuum really efficient; and moreover ether, which is in most respects superior to all the other substances employed, has an awkward tendency, under the influence of frequent condensations and rarefactions, to transform itself into less volatile isomers.

The great characteristic of ice-machines which employ ammonia, methylic ether, or sulphurous acid, as compared with those of the ether type, is that they work at increased instead of diminished pressures, since these substances are gaseous at ordinary temperatures and pressures, and require for their liquefaction either the production of a low temperature or the application of a high pressure. For facility of reference the boiling points and vapour pressures at three different temperatures for these substances are given in the following table. [table]

The best known of the ammonia machines is Carré’s (1859), the principle and construction of which are remarkably simple. Two strong metal vessels, the boiler and refrigerator, are connected above by a tube. In the boiler a saturated solution of ammonia is raised to 130°-150° C. The ammonia is driven over under high pressure into the refrigerator, round which cold water circulates, and in which the ammonia is condensed to a liquid. The boiler is then placed in cold water, and as its temperature falls the pressure in the apparatus is relieved and the liquid ammonia in the refrigerator vaporizes rapidly, thereby producing intense cold, and redissolves in the boiler. The temperature to which the boiler must be raised at first is determined by the condition that the pressure in the boiler must correspond to the pressure of the ammonia vapour at the temperature of the condenser. Now the pressure of ammonia vapour increases from 8£ atmospheres at 20° C. to 11∣ at 30° C.; and this higher pressure is extremely difficult to keep up in such an apparatus as Carré’s, because of inevitable leakage. In warm countries, accordingly, the ammonia-machine is practically useless because of the high pressures required; andin temperate climates, where natural ice can be stored throughout summer, an ice-machine is hot in suc£ great demand. One great drawback to the efficient working of Carré’s machine is the difficulty of keeping the refrigerating liquid free of water—only 75 per cent, of it being ammonia. To remedy this defect Reece invented his machine (1869). The essential part of this ingenious apparatus is an upright cylinder in which a descending current of strong ammonia solution, drawn originally from the boiler, is met by an ascending current of steam. The ammonia is thus separated from the water, and is driven off into a rectifier, from which, after being freed from any small quantity of water it may have carried along with it, it passes into a condenser where it is kept liquid by its own pressure. It is then allowed to collect in the refrigerator, where at the required moment the pressure is relieved, permitting the ammonia to vaporize and escape to a separate chamber to be redissolved. Brine flowing through a coiled tube within the refrigerator is used as the vehicle for the cold produced; or even mere water may suffice if the object is simply to get a diminished temperature without freezing. Linde’s ice-making machine, some twenty-two of which were in operation at the Düsseldorf Exhibition of 1880, is the latest form of ammonia machine; and its inventor claims for it superiority over all others as an economical refrigerator. The danger of explosion, one of the great disadvantages of ammonia, is obviated by carrying the liquefied gas through narrow iron tubes and by employing only a small quantity of the substance at one time. Blocks of ice are formed between the spokes of a revolving drum, which, cooled internally by the evaporating liquid, dips into a tank of water. Methylic ether is in some respects better than ammonia, having a higher boiling point, and requiring smaller pressures, without the necessity of heating. In Tellier’s machine (described in the Annales de Chimie et de Physique for 1874), which is specially suitable for use on board ship, the methylic ether evaporates in a closed metallic vessel, the sides of which are in immediate contact with the water to be frozen or chilled.

Sulphurous acid, first successfully employed as a refrigerating agent by Pictet of Geneva (1876), and thereafter applied by Gamgee to the formation of his glaciarium or artificial skating rink, is in many respects far superior to any other known refrigerator. Thus it is more easily liquefied than ammonia and methylic ether, exerting a vapour pressure of only 4⅜ atmospheres at 30° C.; it has no chemical action upon metals or fats; it is incombustible; it is obtainable at small expense; and it has, besides, good lubricating properties;—in short, it seems to possess all the essentials of an efficient and economical refrigerator. In Pictet’s machine, the liquid sulphurous acid passes under pressure from the condenser to the refrigerator, where on the pressure being relieved it vaporizes, cooling to -7° C. a current of brine which then flows round the tanks containing the water to be frozen. The sulphurous acid gas in the refrigerator is drawn over by an aspirating force-pump and recondensed in the condenser, which is kept cool by an ample supply of cold water. By a special modification of the sulphurous acid machine, Pictet obtained as low a temperature as -73° C.; under this low temperature he then compressed carbonic acid gas to a liquid, by the evaporation of which he produced such intense cold as to enable him to liquefy the so-called permanent gases under a pressure of several hundreds of atmospheres (Dibliothéque Universelle, 1878). Gamgee uses as his congealing liquid a solution of 4 parts of glycerin in 6 parts of water, which is conveyed in pipes beneath the water-surface to be frozen.

Machines which are capable of freezing water may in certain circumstances be much more efficiently employed to produce cooling without...

A good form of ice-house is that recommended many years ago by Mr Bailey, gardener at Nuneham Park, Oxford, and described in the Gardener’s Magazine of Botany (i. 82). This house is shown in section and plan in fig. 1, where the dotted line indicates the ground level. The well or receptacle for the ice a is 10 fest 6 inches wide at the base, and 3 feet wider near the top; the walls are hollow, the outer portion being built of dry rough stone, and the inner wall and dome f of brick. The outer wall e might be replaced by a puddling of clay, carried up as the work proceeds. Over the top is a mound of clay and soil g, which is planted with shrubs to keep the surface cool in summer. The drain i carries off the water formed by the melted ice, and is provided with a trap h to prevent the ingress of air through the drain. There is a porch or lobby b provided with an outer and an inner door c, c ; and there are apertures at d, d, to get rid of the condensed moisture, which, if not removed, would waste the ice. These ventilating doors should be opened every night, and closed again early in the morning. The most important conditions to be secured are dryness of the soil and of the enclosed atmosphere, compactness in the body of ice, which should be broken fine and closely rammed, and the exclusion as far as possible of air.

The Americans, who use large quantities of ice, always store it above ground. One of their ice-houses, of which the elevation is shown in fig. 2 and the plan in fig. 3, described in Allan’s Rural Architecture, is both simple and ornamental in character. The house may be 12 feet square, or any larger size. A series of posts in pairs are set up 1 ∣ feet apart and 8 feet high, about 1 foot being inserted firmly in the ground; the distance between each pair is 3 feet. The tops being cut level all round, a plate 6 inches wide and 4 to 6 inches deep is spiked on to each line of posts, the two plates being strongly stayed by cross pieces so as to form a double frame. The inner face of each line of posts is now boarded up closely, leaving a space 6∣ feet by 3 feet at the sides, which are also boarded, to form a door-casing on each side. The spaces between the two lines of boards thus form a continuous box, which is to be completely filled up with moist tan, bark, or sawdust, well packed throughout. There must be a drain to carry off all water from the interior. Within the enclosed space some level joists are laid down, and on them loose planks to form a floor, which when covered 1 foot thick with straw is ready to receive the ice. The roof is formed of rafters, 4 inches by 3, long enough to project at least 4 feet outside the plates, to which they must be well secured by spikes. The rafters are tobe boarded over and covered with shingle, and a small opening left at the top to admit a pipe 8 inches in diameter for a ventilator,over which a small ornamental cap, supported on four little posts, is to be placed. As a finish to the projecting roof, brackets of 3 by 4 inch scantling, if the joists are of sawed stuff, or of rough limbs of trees to match the posts, if these are rough, may be introduced. After the ice is stored, a close floor of boards should be laid on joists resting loosely on the wall plate (to admit of this upper floor being removed while the house is being filled), and they must be covered with 6 inches of tan or sawdust, or failing these with straw. A good layer of tan or sawdust should also be placed on the top of the ice when it is put in. There should be two doors, inside and outside the lining, both opening outwards. A shady place is desirable, but not essential.

A still less expensive way of storing ice has been described by the late Mr Pearson of Kinlet in the Gardener’s Journal (iii. 10). In this case the ice-stack was made on sloping ground close to the pond whence the ice was derived. The ice was beaten small, well rammed, and gradually worked up into a cone or mound 15 feet high, with a base of 27 feet, and protected by a compact covering of fern 3 feet thick. A dry situation with a sloping surface is necessary where this plan is adopted, and a small ditch should surround the heap, to drain away any water that may come from melted ice or from other sources.

The whole of the south coast, from Hornafjöröur in the south-east to Reykjanes in the south-west, is entirely unbroken by bays or firths. If such ever existed, they have been filled up by the glaciers and the sand and mud carried down from the volcanic ice-mountains situated close to the south coast. The coast-line is not, however, a straight line, but a broad arch, as the land swells out in the middle southwards to a considerable extent. On the north of Reykjanes a broad bay called Faxafléi (Faxi’s Bay) cuts into the land; it is bounded on the north side by Snaefellsnes, and has an area of 54 miles by 30 On the north side of Snaefellsnes the long Breiöifjöröur (Broadfirth) nearly cuts off the north-west peninsula from the rest of the island; it is 80 miles long and 40 broad. The Breiöifjöröur is noted for its great number of small islands, most of them inhabited, and all of them affording breeding places for the eider duck. To the north of the Breiöifjöröur, innumerable bays cut into the peninsula at every turn, giving it somewhat the look of the outstretched hand of a man; the longest of these is ÎsafjarÔardjùp (Icefirthdeep), 45 miles long. On the north side of the island, between Horn (Cape North) on the west and Melrakkaslétta (Fox Plain) on the east, there are several large firths. Furthest to the west is Hûnaflôi (Bearcubs’ Bay), about 60 miles long, which nearly meets the Breiöifjöröur running in from the west; the tongue of land which separates them and connects the north-west peninsula with the rest of the island is hardly 5 miles broad. The other firths on the north side are Skagafjöröur, Eyafjöröur (Firth of the Isles) 36 miles long, Skjälfandafjöröur, and Axarfjöröur (Axefirth). The Melrakkaslétta is separated from Langanes, the north-east point of Iceland, by the pistilfjöröur (Thistlefirth). The whole of the east coast of the island is indented by numerous narrow firths like those found in the north-west peninsula, but none of them are of any great length. Sailing round the island from point to point, the distance is 900 miles, but if we follow the coast-line it is not less than 2000 miles.

The centre of the island is a table-land, or rather a broad flattened ridge, sloping down to the north and the south, the average height of which above the level of the sea is about 2000 feet. It consists of arid sands and rugged tracts of lava, the most important of which bear the names of ÔdâÔahraun (the Lava of Evil Deeds), Sprengisandur (Bursting Sand), and Stérisandur (Big Sand). This wilderness is frequently broken by high and extensive ice-hills called jökull (plur. jöklar). The ice hills rise to the greatest height in the south-east, where the most extensive ice-field in the island, called Vatnajökull, covers about 4000 square miles. The outliers of this ice-field come close down to the water, hardly leaving room for passage between them and the sea; some of these are the loftiest summits in the island, as Ôraefajôkull, which is 6466 feet high. South of the west end of the Vatnajökull, called Skaptärjökull, stretches an inhabited slope, interrupted by several small hills, and intersected by considerable streams. The eastmost part is called SiÖa; then follow Landbrot, MeÖal-land, and Alptaver. West of this the land rises again in the Myrdalsjökull and the Eyafjallajökull, the latter being 5593 feet high, and here again the mountains come close down to the sea. West of the Eyafjallajökull is the largest plain in the island, stretching westward to the mountain chain terminating in the low cape of Reykjanes, and backed on the north side by several isolated mountains, among which the far-famed Hecla is prominent; its height approaches 5000 feet. This plain consists of stretches of grass land and marshes, affording abundance of grass for pasture and haymaking.

The southern and part of the eastern coasts of Faxafléi, as far as Reykjavik, are very barren and desolate, being almost entirely rugged lava tracts; but the lower parts of the hills then begin to be clothed with grass, affording pasture for sheep, cattle, and horses. North of Reykjavik is a long and narrow firth called HvalfjörÖur (Whalefirth), and further on a shorter one called Borgarfjöröur (Burghfirth). Between the extremity of the latter and the central highlands there is a large and fertile district, consisting of grassy valleys, divided by low hills, and an extensive plain covered with marshy grasslands. This district is a fair specimen of many of the inhabited parts of Iceland. The level land, the valley bottoms along the river banks, and in many cases the slopes of the hills, are covered with grass, but the soil is too frequently boggy and marshy. The hills are partly covered with heather, and in a few places with stunted dwarf birch. Districts similar in character to Borgarfjöröur are the Dalir (Dales) on the south side of Breiöifjöröur, the Hûnavatnssÿsla on the south side of Hûnaflôi, the Skagafjöröur, the FljétsdalshéraÔ on the east side of the island, and the western half of the plain lying between Eyafjallajökull and the Reykjanes range of mountains. The north-west peninsula consists, as already stated, of narrow firths divided by high and narrow mountain ridges, seldom lower than 2000 feet. In some places the top is a thin rocky edge; in others it consists of sharp-pointed peaks, denuded of all vegetation. Even at a considerable distance the different rocky strata may be distinguished. Sometimes these hills, or rather cliffs, rise perpendicularly out of the water to a height of a couple of thousand feet, affording breeding-places to an immense number of sea-fowl. More frequently the lower parts of these razor-backed hills slope towards the firths, the stony slopes being partly covered with grass or heather. The farms are therefore found along the shores and in short valleys cutting into the hills from the ends of the firths. The east coasts of Iceland present exactly the same character as that of the north-west peninsula. From the end of Eyafjöröur a long and fertile valley, bounded on both sides by lofty mountains, runs due south into the country for about 25 miles. The north-east corner of the island, called pingeyarsysla, has good sheep pasturage, although its hills and slopes are covered with heather instead of grass to a greater extent than most other districts of the island. It will thus be seen that the inhabited parts run round the coasts, and from the end of the bays into the interior, the farms farthest inland being about 50 miles from the sea.

As the snow-line is at an altitude of from 2500 to 3000 feet, all the highest mountain-tops are cones covered with perpetual snow. Besides the ice-mountains already mentioned, there are several on the western part of the central highlands, such as Hofsjökull, Langjökull, Eiriksjökull, &c.; Snaefellsjôkull, at the point of the peninsula separating the Faxaflôi and Breiftifjöröur, reaches the height of 4713 feet. All these mountains are snow-capped. Most parts of the island are studded with hills ranging in height from 2000 to 3000 feet. The tops are usually bare and rocky, but the slopes are to some extent covered with grass and heather.

Most of the mountains of Iceland have been volcanoes, and at least twenty-five of them have been active within the historical period of the island, that is, the last 1000 years. It was observed by Mackenzie that there are two volcanic formations in the island, one consisting of flat sheets of basalt, the other of more irregular hilly accumulations of trachyte, obsidian, ashes, and other volcanic masses. The former of these, there can be little doubt, is of Tertiary age—a part of the great Miocene volcanic plateaus, which on the one hand extend southwards through the Faroe Islands and the west of Scotland to the north of Ireland, and on the other stretch northwards and westwards far into Greenland. The other volcanic masses are of recent date. Iceland has thus been the theatre of volcanic activity at two widely separated periods, though we do not yet know whether during the interval the activity was wholly dormant. Of the existing volcanic mountains the best known is Hecla, from which eighteen eruptions have been recorded; the last took place in 1845-46. The intervals between the eruptions have varied greatly; sometimes it has remained quiet for six years only, at other times for seventy-two years. As with most other volcanoes, the height of this mountain varies with the eruptions. Thus before the eruption of 1845 its height was given on Gunlaugsson’s map as 4951 feet, while Kjerulf measured the mountain in 1850, and found it to be only 4532 feet. The earliest historical eruption, that of 1104, is celebrated as the “sand-rain winter,” the second, in 1158, as the “great darkness,” from the quantity of ashes ejected. One feature of the Icelandic eruptions, not from Hecla only, but from other orifices in the island, has been the prodigious quantity of fine dust discharged and the great distance to which this material has been carried. Thus in the year 1766 a column of ashes rose out of the crater of Hecla to a height of 16,000 feet into the air. Volcanic dust from the Icelandic vents has frequently been borne by upper air currents so as to fall upon the Faroe Islands, and has even been carried in considerable quantities as far as Norway on the one side and the north of Scotland on the other. Next to Hecla, the Katla, or Kötlugjä, in Myrdalsjökull may be mentioned; its last eruption (the thirteenth known) took place in 1860. The most tremendous volcanic outbreak in Iceland was that which took place in 1783 in or near the Skaptàrjôkull, on the north-west border of the Vatnajökull. Two principal lava streams flowed from it: one of them was 50 miles in length, from 12 to 15 miles in breadth, and 100 feet deep, and the other was 40 miles in length. It has been calculated that these two streams cover an area of 420 square miles. This eruption destroyed directly or indirectly one-sixth of the inhabitants of the whole island, or one-half of all the live stock. From nearly all the outliers of the Vatnajökull eruptions now and then take place. To the north of Vatnajökull a range of volcanic centres extends as far as Myvatn. The last outbreak here took place in 1875, when fine volcanic dust was discharged in great quantity, some of it being carried as far as Norway. The sea around the coasts of Iceland has been frequently disturbed by volcanic outbreaks, especially off Cape Reykjanes.

On account of the same volcanic activity, hot springs are frequently met with throughout the island. The common name for them in Icelandic is “hverr” (cauldron). The chief of these hot springs is Geysir (Gusher). See Geysers.

The only mineral worked to any extent in Iceland is sulphur; the principal mines are those of Krisuvik and Mÿvatn. Of the Iceland spar used for polarizing optical instruments, only one mine has been worked, that of Helgusta5ir in the east of the island. Limestone is found near Reykjavik, and has been worked a few years. Ironore is found in many parts of the island, but not in paying quantities, as suitable fuel is wanting. Aluminium occurs near Cape Reykjanes, but no attempt has been made to work the mine. Coal has also been found in one place, but has not been worked. There are considerable quantities of lignite, called in Icelandic surtarbrandur, in the north-west peninsula; some successful attempts have been made to use it as fuel, but it has not been worked to any extent. Peat is found, and is used as fuel, in most parts of the island.

Iceland is rich in streams and rivers, some of them carrying a large volume of water; as, however, the fall is steep in every case, they are not navigable even by small boats. The longest are pjérsâ, running southwards from the central highlands, and Skjâlfandafljét and Jôkulsâ ά Fjöllum in the north-east, running northward. The last-named river is 113 miles in length, the other two 108 miles each. Of other rivers may be mentioned the Hvit⅛, part of which is called Olfusâ, running nearly parallel with pjérsâ, Hvïtâ in BorgarfjörÖur, Blanda running into Hûna-fléi, HéraSsvôtn in SkagafjörÖur, and Lagarfljét in the east. There are several rivers named Hvit<4 (white river), so called from their milky waters, caused by the glacial •mixtures carried down from the highlands. The principal waterfalls are—Skégafoss and Seljalandsfoss, south of Eyafjallajökull, Godafoss in Skjâlfandafljét, and Dettifoss in Jôkulsâ â Fjöllum. Of the lakes pingvallavatn, about 25 miles north-east of Reykjavik, and Mÿvatn in the north-east of Iceland are the largest. The former is 25 miles in circumference, and the latter 36 miles; its waters are studded with thirty-four small islands, affording breeding-places to ∙a large number of water-fowl.

The climate of Iceland is not nearly so severe as might be supposed from the latitude. At Reykjavik the mean temperature of the year is 39° Fahr., of the summer 53° and of the winter 29° 18'. The temperature of Akureyri is 32° for the year, that of the summer 45° 5' and the winter 20° 7'. There is therefore great difference between the north and the south of the island. Another difference may also be noticed; while the climate of the south is wet and variable, that of the north is dry and regular. The mean temperature of different years sometimes varies as much as 10°, and the mean temperature of the same month has been known to vary as much as 27°. One feature in the climate has been noticed by all travellers, that is, the clearness and purity of the atmosphere, rivalling that of Italy, mountains being seen distinctly at a distance of 100 miles. The rainfall is considerable in the south and the east of the island, and snow-storms and gales are frequent in winter. Thunderstorms occur mostly in winter.

No cereal is grown in Iceland, but in some places there is found a kind of wild oats (Avena αrtηαriα), called in Icelandic “melur.” Potatoes, carrots, turnips, and several kinds of cabbage have lately been cultivated with considerable success. The grasses, wild and cultivated, are of the greatest importance to the inhabitants. The only trees found are the dwarf birch, rarely higher than 12 feet, and some willow and juniper bushes. The wild flora of Iceland is small and delicate, with bright bloom, the heaths being especially admired. Wild crowberries and bilberries are the only kind of fruit found in the island.

The only wild animal in Iceland is the fox, of which both white and blue varieties occur; they are hunted for their skins, and also because they often attack the sheep. The domestic animals are the cow, the horse, the sheep, the dog, and the cat. The cows are of a small breed, resembling English shorthorns in general, and especially Alderneys. The horses are also of a small breed, the average height being twelve hands; they are hardy and enduring; many of them are never housed, and forage for themselves as best as they can throughout the winter. They are exported to Great Britain in considerable numbers, for use in the coal mines. The sheep generally are of nearly the same size as the Scotch blackfaced sheep; they are not unfrequently sβv,n with three or four horns. The genuine Iceland dog, with his pointed snout, short ears, curled tail, and short legs, has some resemblance to the Esquimaux dog and the Scotch collie. Reindeer were imported in the last century, but they fled to the mountains and became wild; they are now nearly extinct. There are said to be ninety different species of birds, fifty-four of them being water-fowl. The most remarkable of the birds of prey are the Icelandic falcon (Falco islandicus) and the eagle. The only game bird is the ptarmigan, which is brown in summer and white in winter. Of the water-fowl the eider duck is of the greatest importance on account of its valuable down; the killing of it is therefore forbidden by law. Immense numbers of gulls, puffins, and guillemots are seen near their breeding places on the small islands and on the cliffs round the coasts. The hooper, or whistling swan, is found in large numbers in Iceland. The sea round the coast teems with cod, haddock, holibut, and the basking shark; the fin-backed-whale and seals of various kinds are also met with, but in smaller numbers. In the lakes and rivers salmon and trout are caught in considerable quantities.

As no corn is grown, there is no agriculture to speak of, and only a little spade husbandry connected with the cultivation of kitchen gardens, where potatoes, turnips, and carrots are grown. The area thus under cultivation covers, according to the latest official returns, about 215 English acres throughout the island. The cultivation of the soil in Iceland can hardly indeed be said to have been attempted; such experiments, however, as have been made, have given good hope of success. Around every farmhouse is a field called “tùn,” which is but rarely enclosed or fenced. This is the only part of the land which is cultivated at all, and all that is done there is to spread dung on the top of the soil in autumn and scrape it off in spring. Even this most primitive cultivation makes the grass twenty-five to fifty per cent, better than elsewhere. The haymaking season extends from the middle of July to the 20th of September. The grass is cut with small scythes, first in the home field, and then on the uncultivated grass-lands belonging to the farms. Many of the fishermen hire themselves to the farmers during the haymaking season; and during the fishing season the farmers send their servants to the sea-coast to fish.

According to the latest official returns the cattle in the island numbered 20,378, the horses (ponies) 31,312, and the sheep 415,339. It is obvious, however, from the quantities of wool exported that the number of sheep must be at least double that stated in the returns.

The manufactures are confined to spinning, weaving, and knitting the wool of the sheep. A sort of tweed, called in Icelandic “vaftmal,” is the principal clothing of the inhabitants. The spinning of the yarn is done by the women in winter, and almost every farm has an old-fashioned loom. In the north considerable quantities of jackets and stockings are knitted and exported.

The trade with Iceland is entirely in the hands of Danish traders and a few Icelanders—who mostly reside in Copenhagen. It consists almost entirely in exchange, or barter. The principal exports of the Icelanders are cod fish, about 6,000,000 ft> annually; train oil, 9500 barrels; wool, 1,500,000 5); eider down, 7000 lb; and feathers, 20,000 lb. Ponies are now exported to Scotland,—about 2000 a year; and a few cargoes of live sheep have been sent over during the last two years. All bread stuffs have to be imported, as well as groceries, spirits, wines, and beer, tobacco, salt, building materials, and other items. Since 1854 the trade has been open to all nations; but any vessel trading with Iceland had to take out a sea pass at the cost of 2s. 3d. per ton down to 1879, when this duty was abolished. On the other hand, a trifling duty has been laid on spirits and tobacco.

There being no roads in the island, but merely tracks trodden down by the feet of the ponies, there are no carts nor carriages of any description. In the firths boats are chiefly used for conveying goods and passengers; but all inland communication and conveyance is by ponies. These hardy animals carry each a burden of about 200 lb weight, under which they walk about 25 miles a day. All travelling...