Wood Tar.— Wood tar, known also as Stockholm and as Archangel tar, is principally prepared in the great pine forests of central and northern Russia, Finland, and Sweden. The material chiefly employed is the resinous stools and roots of the Scotch fir (Pinus sylvestris) and the Siberian larch (Larix sibiηca), with other less common fir-tree roots. A large amount of tar is also prepared from the roots of the swamp pine (P. australis) in North and South Carolina, Georgia, and Alabama, in the United States. In the distillation of wood a series of products, including gas, tar, pyroligneous acid and wood spirit, and charcoal may be obtained, and any of these may be the primary object of the operation. When tar is the substance sought, the ancient and crude method of working is yet largely adopted in the north of Europe. The wood to be treated is closely piled up into a huge conical stack or pile on an elevated platform, the sole of which is covered with clay and tiles. The sole slopes inwards from every side to the centre, where an opening communicates with a vaulted cavity under the elevated platform. The pile of wood is closely covered over with layers of turf and earth or sand to a depth of several inches, but leaving at first near the bottom numerous apertures for the admission of air to promote ignition. The pile is ignited from below, and as the fire spreads through the heap the various apertures are closed up and a slow smouldering combustion goes on for some days till, by the sinking of the pile, the top of the stack falls in, and a bright flame springs up at that point. About ten days after ignition tar first begins to flow, and it is at once collected into barrels. According to the size of the pile, the distillation may continue several weeks, the tar secured amounting to about 17 - 5 per cent, of the w ood operated on. In this method several valuable products—the gas, the crude pyroligneous acid, and much charcoal—are lost or wasted; and a more economical process of treating the wood in closed stills or retorts is now largely used in Russia, the gas evolved serving as fuel under the retorts. The heavier tar products of the distillation collect at the bottom of the retort, whence they are carried off by a pipe to a receiver; the volatile portion passes off at the upper part of the retort, and is separately condensed, the lightest portion passing through a worm condenser. From treatment in close retorts resinous roots yield from 16 to 20 per cent, of tar, with some oil of turpentine and pyroligneous acid.

Wood tar is a semi-fluid substance, of a dark brown or black colour, with a strong pungent odour and a sharp taste. Owing to the presence of acetic (pyroligneous) acid, which is a collateral product, it has an acid reaction; it is soluble in that acid, as well as in alcohol and the fixed and essential oils, <fcc. Tar consists essentially of a mixture of homologous hydrocarbons, and by redistillation it can be fractionated into a series of bodies having fixed boiling points. Some varieties of tar have a granular appearance, from the presence of minute crystals of pyrocatechin, which dissolve and disappear on heating the substance. Pyrocatechin dissolves freely in water, and to it the tar water (liquor picis) of pharmacy probably owes its value.

Crude tar from retorts, when submitted to redistillation, gives off w ood spirit (methyl-alcohol), and then acetic (pyroligneous) acid, and finally, on forcing the heat, pitch oil is driven off. The residuum left in the still hardens into a solid vitreous mass, which forms the black pitch of commerce. Tar and pitch are most largely used as protective coatings for woodwork and other materials much exposed to water and the weather. Thus tar is of great value in connexion with shipbuilding and shipping generally. A considerable quantity is used in manufacturing tarred ropes, and in the “smearing” of highland sheep to afford a protection against the weather. Pitch also is the basis of the Berlin black or Brunswick black used for coating cast-iron goods and for “japanning” preparations.

Coal Tar.— The art of distilling coal for the production of tar was discovered and patented by the earl of Dundonald in 1787, and till the general introduction of coal gas some amount of coal was yearly distilled in Scotland for the production of coal tar. The demand for the substance was limited, it being principally used for coating iron castings and smith work, for making an inferior lamp black, and as a source of a solvent oil. With the extensive use of coal gas the necessity for this separate distillation ceased, and soon tar was produced in the manufacture of gas in quantities that could not be disposed of. It was burned up for heating gas-retorts; it was mixed with coal dust, sawdust, <tc., for making patent fuel; and it was distilled for producing a series of hydrocarbon oils, heavy tar, and pitch; but it was only after the discovery and introduction of “tar-colours” that the substance came for some time to be really valuable. Since that time its price has fluctuated greatly; and in the United Kingdom alone there are now distilled annually about 10,000,000 tons of coal for gas-making, producing 120,000,000 gallons of crude tar,—a quantity greatly in excess of the ordinary demand.

If wood be distilled slowly at low temperatures, the gases consist chiefly of carbonic oxide and carbonic acid, mixed with only very little of carburetted hydrogens, and consequently little luminous on combustion; the watery part of the tar includes relatively much of methyl-alcohol, acetone, and acetic acid; the oily part of the tar (tar proper) has a certain proximate composition characteristic of this mode of distillation. Our present knowledge in regard to this last-named point is very incomplete; of definite species the following have been discovered :—

(1) Phenol, C 6 H 5 OH (synonym carbolic acid).

(2) Cresol, (C 6 H 4 .CH 3 )OH.

(3) Phlorol, (C 6 H 4 .OH)C 2 H 5 .

(4) Pyrocatechine, (C 6 H 4 )(OH) 2 , one of three isomerldes.

(5) Guaiacol, C 6 H 4 ∣q^ h , methyl-ester of No. 4.

(6) Homo-pyrocatechjne, {C 6 II 3 (CH 3 )j(0Il) 2 .

(7) Creosol, {c 6 H 3 (CH 3 )j-øc H 3, methyl-ester of No. 6.

Genuine creosote consists of (1), (2), (5), and (7). In addition, there are numberless bodies which still await scientific definition.

If the distillation of wood is carried out at a very high temperature,—if, for instance, the wood is placed in a relatively large retort previously brought up to a bright red heat and kept at such temperature, or if the vapours produced at a relatively low temperature are passed through intensely heated pipes before reaching the condenser (Pettenkofer’s method for producing illuminating gas from wood),—the gas produced contains a considerable admixture of luminiferous hydrocarbons, the proportions of methyl-alcohol, acetone, and acetic acid get less, and the tar proper assumes more of the character of coal-gas tar (see below). Similar observations we make in the case of coal. About 1862 Wigan cannel coal used to be distilled industrially at low temperatures to produce “light oils.” Schorlemmer examined these and found them to consist chiefly of “paraffins” (see Paraffin) from C 5 H 12 upwards. A similar result is obtained with ordinary coal, although in its case the “benzols” are more largely represented. If we distil any kind of coal at high temperatures— i.e. , in the way customary for illuminating-gas making—the distillable part of the tar proper consists chiefly of benzene, C 6 H β , and benzene-derivatives, i.e., benzols, C 6 H β + nCH 2 j phenols, C 6 H 6 O, and homologues, (C 6 H 5 .πCH 2 )OH; amido-bodies, C 6 H 5 NH 2 (aniline), and homologues; condensed benzols, such as naphthalene, C 10 H 8 = 2C 6 H 6 -C 2 H 4 5 anthracene, C 14 H 10 = 3C β H 6 -C 4 H 8 ; chrysene, Ci 8 H 12 = 4C β H g - C 6 H 12 , &c. The paraffins then become an altogether subordinate feature.

A great and meritorious research of Berthelot’s has thrown considerable light on the chemical mechanism of dry distillation. As found by him, even the most complex of the substances named are producible by the interaction upon one another of a few bodies of very simple constitution, or even one or other of these by the mere action of a high temperature. To give a few examples. Marshgas, CH 4 , when passed through red-hot tubes, yields olefines, C 2 H 4 , C 3 H 6 , C 4 H 8 , &c., with elimination of hydrogen, H 2 . The same CH 4 , if subjected to a spark-current (t.e., local application of intense heat), yields acetylene and hydrogen, 2CH 4 =∙C 2 H 2 + 3H 2 , and the acetylene produced passes partly into benzene, C 6 H 6 =3C 2 H 2 . Ethylene, C 2 H 4 , when passed through a porcelain tube kept at a moderate red heat, yields benzene, C 6 H β , styrolene = phenyl - ethylene, C 2 H 3 .C 6 H 5 , naphthalene, C 10 H 8 , and perhaps also its hydride, C 10 H 10 . Acetylene, qua potential benzene, and ethylene yield styrolene and hydrogen, C 6 H 6 + C 2 H 4 = C 6 H 5 .C 2 H 3 + H 2 j and styrolene plus ethylene yields hydrogen and naphthalene, C 10 H 8 ,

Benzol at a high temperature loses hydrogen, and, so to say, doubles up into di-phenyl, C 12 H 10 ; and this latter, when heated with ethylene, yields anthracene, C 14 Hι 0 , and hydrogen, ^12∏10 ^t 0 2 H 4 = C 14 H 10 + 2H 2 . Conversely, hydrogen may, so to say, turn out its equivalent of a hydrocarbon; thus, for instance, chrysene, C 18 H 12 + 2H 2 , yields di-phenyl, C 12 H 10 , + benzene, C 6 H 6 .

Pyrogenic reactions generally are reversible; thus, any of the following three equations is correct, whether we read it from the left to the right or from the right to the left :—

(1) C 2 TI β (ethane), at a red heat becomes C 2 H 4 +H 2 .

(2) Ci 2 H 10 +C 6 H 6 =C 18 Hi 2 +2H 2 .

(3) Cι 4 H 10 q-2H 2 =2C β H β +C 2 H 2 .

Hence no single pyrogenic reaction goes to the end; if it does not, so to say, check its own progress, other secondary reactions set in and do so, the general result being that ultimately, but in general slowly, a state of dynamic equilibrium is attained in which a set of synthetic reactions on the one hand and a set of analytic reactions on the other compensate one another.

Industrial Working of Coal Tar. 1 — Coal tar, as it comes from the gas-works, is used for a variety of purposes, such as—(1) for fuel, the tar being made into a spray by means of a steam-injector and the spray kindled; (2) for the preservation of building materials, porous stones, and bricks, &c.; (3) for making roofingfelt (in 1868, five-sixths of the 9000 tons of tar produced at the Berlin gas-works was thus utilized; the case, however, is different now); (4) for making a low quality of lamp-black. At present, however, most of the tar produced, in centres of industry at least, is worked up by distillation. The tar as it comes from the gasworks is allowed to rest in a “pond” until the tar-water (solution chiefly of ammonia and certain ammonia salts) has gone to the top. The tar proper is then pumped into a large wrought-iron still (of upright-cylinder form preferably) and therein subjected to distillation over a naked fire. A necessary preliminary, however, is the removal of the unavoidable remnant of water, which is best effected by cautiously heating the tar in the still so as to render it more fluid and enable the water to rise to the top and then letting the upper stratum run out by an overflow tap at the side. The distillation is then started. It involves the formation of two sets of volatile products, namely—(1) combustible gases (including sulphuretted hydrogen and bisulphide of carbon vapour), which must be led away to avoid nuisance and danger of fire, and (2) a very complex liquid or semi-liquid distillate. This latter is collected in successive fractions, generally in this manner:—(1) as “first runnings,” what comes over at temperatures below 105° to 110° C.; (2) as “light oils,” at temperatures between 110° and 210° C.; (3) as “carbolic oil,” at temperatures between 210° to 240° C.; (4) as

“creosote oil,” at temperatures between 240° to 270° C.; (5) as anthracene oil, at temperatures above 270°.

In the earlier part of the “first runnings” and light-oil period the condenser must be kept cold; towards the end it must be kept warm to prevent choking by solidified naphthalene. In practice, the operator does not go entirely by the boiling point, but to a great extent by the specific gravity of the distillate, which, in general, increases as the boiling point rises. As soon as a drop of the last runnings floats in water (exhibits the specific gravity 1), the “light oil” is supposed to be over. That the fractionation is not always and everywhere effected in the same way needs hardly be said. If the manufacture of carbolic acid is aimed at, it is best (according to Lunge) to select the fraction 170° to 230° C. for this purpose. Naphthalene boils as high as 217°, yet a deal goes into this carbolic-acid fraction. As soon as naphthalene begins to crystallize out largely (on cooling down a sample of distillate), the carbolic acid may be presumed to be over. What follows next is put aside as creosote oil, until, after the disappearance of the naphthalene, a new solid product, namely, anthracene, begins to show itself. With any tar that contains a remunerative proportion of anthracene, the anthracene oil is the most valuable of the products, as the raw material for the making of artificial alizarins.

Supposing the anthracene to have been extracted as completely as practicable, the residue in the still consists of “hard pitch,” a viscid black fluid which on cooling freezes into a fragile solid. In former times more commonly than now “soft pitch’’used to be produced by leaving more or less of the anthracene oil and even creosote oil in the still. At the end of the anthracene stage of the distillation it is as well, if not necessary, to help the very high boiling vapour out of the still by means of superheated steam, and to keep the worm at 100° C. to prevent choking. At a German establishment a vacuum is used with great advantage.

We come now to explain briefly how the several fractions are worked up.

The pitch (which we assume to be “hard pitch ”) must be run off hot through a tap at the bottom of the still and led into a low-roofed and well closed-in “house,” because it would take fire in the open air. After it has cooled down sufficiently in the “house,” the pitch is run into pitch-holes in front of the house and allowed to freeze there. The depth of pitch in a hole is about 12 inches. The solid pitch is hacked out with pickaxes and sent into commerce. A superior apparatus for the recovery of the pitch, which precludes all danger of conflagration and many inconveniences of the ordinary system, has been devised for the Paris gas-works by Régnault. 2 Lunge found, from many distillations, that tar from the midland counties yields about 55 per cent, of hard pitch.

Hard pitch is used chiefly for making the following. (1) Asphalt.— The pitch is fused up—perhaps in the still which produced it—with the requisite proportion of creosote and anthracene oil, previously freed from their valuable components. Such asphalt is used for street-paving, t.e., filling up the spaces between the paving-s*tones, and, in admixture with sand and generally more or less of natural asphalt, for the making of footpaths and floorings generally. In Germany it serves for the making of pipes for conveying acid liquids in works and chemical laboratories, &c. Endless hemp-paper is soaked in liquefied asphalt and wound spirally around an iron core, previously smeared over with soft soap, in about 100 layers. The whole is then exposed to strong pressure while still hot, and is separated from the core after being allowed to cool. Such pipes stand almost any kind of acid, but they must not be used for hot liquids. (2) Varnishes.— The pitch is dissolved in suitable tar oils,—creosote oil for a lower and light oil for a higher quality. (3) Coke.— In former times more frequently than now pitch was made into coke by transferring it to a special flat still and distilling as long as any volatile products came off. The coke which remains is a very pure and consequently valuable fuel. (4) Lamp Black (as a last resource, if no other mode of utilization is practicable).—The pitch is subjected to partial combustion on hot iron plates and the smoke conveyed into chambers to deposit its carbon. The yield is about 40 per cent.

Anthracene Oil.— The oil is allowed to stand cold for a week or so until the anthracene has crystallized out as completely as possible. The mother-liquor is then eliminated, the bulk by means of a filter-press, the rest, at a higher than the ordinary temperature, by hydraulic pressure. The crude product includes far more than half its weight of impurities—phenanthrene, paraffin, naphthalene, &c. To remove these as far as possible, the crude anthracene is ground up and treated with petroleum spirit (boiling at 70° to 100° C. ) or coal tar naphtha (12(r to 190°), in which real anthracene is relatively insoluble. The insoluble part is separated by filtering arrangements and presses (so constructed as to avoid danger of fire), and at last sublimed, more with the view of bringing it into a customary convenient form than with the object of effecting further purification. Such final anthracene may contain 50 to 65 per cent, of pure substance. The only reliable method for 1 For wood tar, see wood Spirit and Vinegab. 2 It is described in Lunge’s Treatise on the Distillation of Coal Tar, London, 1882. to which this article is largely indebted.

determining its strength is to convert a known weight into anthraquinone, C 11 H 10 O 2 , by boiling it with a glacial acetic acid solution of chromic acid, separating out the quinone by diluting with water, collecting and -weighing the product. One part of quinone corresponds to 0'8558 of anthracene.

Creosote Oil is either used as it is for pickling timber, softening of pitch, &c., or else redistilled to extract from it what there is of anthracene oil and carbolic acid oil, which are worked up with the respective principal quantities.

Carbolic Oil.— Assuming this oil to have been collected (as it should be if intended for the making of carbolic acid) between 170° and 230°, the process of extraction is, briefly, as follows. The oil is mixed with a suitable proportion of caustic-soda ley (ascertained by an assay) in an iron vessel at 40° to 50° C. Charles Lowe recom-' mends ley of l - 34 sp. gr., diluted with water to five times its volume. After settling, the aqueous layer is withdrawn into a lead-lined vessel, and the soda supersaturated by sulphuric acid. Crude carbolic acid rises to the top as an oil, and is withdrawn to be sold as such or purified. See Carbolic Acid. Naphthalene abounds in the oil left after extraction of the carbolic acid by caustic soda...

The total area under crop in 1884-85 was 254,288 acres, of which rice occupied 92,186 acres, wheat 54,627, and other food grains 80,304 acres. There are no manufactures worthy of note, and the chief trade is the export of grain. The gross revenue in 1884-85 amounted to £42,048, the land yielding £35,507. The Tarai came under British rule at the time (1802) when Rohilkhaud was ceded to the East India Company. The Government is said to have looked with indifference on this uninviting tract, but since 1831, when the revenue settlements were revised, this reproach has been less deserved. With an improved system of embankments and irrigation in 1851, the formation of the Tarai into a separate district in 1861, and its complete subjection to Kumâun in 1870, the moral and material history of this tract has greatly improved.

The tarantula is widely distributed in southern Europe, round the shores of the Mediterranean. It occurs throughout Spain and is found in southern France, and extends into Asia. In Italy it is said to be especially common in Apulia, round the town of Taranto, from which place the name of this spider is usually derived. A species has also been described from northern Africa. It is usually to be found in dry pieces of waste land exposed to the sun. It lives in an underground passage, which it digs for itself and lines with its web. These passages are round in section, and sometimes an inch in diameter, and may extend to a depth of a foot or more below the surface. The tube first descends vertically for some inches, then bends at an obtuse angle, becoming vertical again near its closed end. The tarantula takes up its position at the first bend, where it can command the entrance, on the lookout for prey. In some cases the tube is prolonged above the surface of the earth by the formation of a small funnel, built up of fragments of wood and earth, and lined like the walls of the tunnel by the web. The females show considerable maternal care for their offspring, and sometimes sit upon their egg sacs; and the species, although somewhat fierce and combative amongst themselves, are capable of being tamed.

Tarantism. The tarantula has given its name to one of those dancing manias which overspread Europe during the Middle Ages. The bite of the spider threw the sufferer into a depressed state of melancholy, accompanied by various nervous disorders. The condition was accompanied by an increased sensibility to the power of music. The excitement of the nervous system amounted in some cases almost to insanity. The symptoms of the patient seem to have varied a good deal with the character of the individual attacked: the most common were a lividity of the body, icy coldness, great depression, nausea, sexual excitement, and loss of sight and hearing. The only means of arousing the sufferer from the lethargy into which he sank was music. Under the influence of this he awoke as it were, and commenced moving rhythmically, then began to dance, and continued increasing the rapidity of the motion until he fell exhausted to the ground. By this means it was considered that the poison of the tarantula was distributed through the system and worked out through the skin. If the music ceased whilst the patient was dancing, he at once sank back into the state of lethargy from which he had been aroused, but when thoroughly exhausted he generally awoke relieved and cured at least for a time. This dancing mania became contagious: one person caught it from another quite independently of the bite of the tarantula, and in this way whole districts became affected. One of the most peculiar characteristics was the attraction that bright pieces of metal, or brilliant pieces of colour, exercised over the imagination of the dancers. This was particularly marked in the later history of the disease. Each sufferer apparently admired one particular hue, the sight of which seemed to cause him the greatest rapture. Red was a very general favourite, though this colour threw St Vitus’s dancers into a frenzy of rage; green, yellow, and other colours also had numerous admirers. Other colours, on the contrary, they detested, and attempted to destroy articles of the obnoxious shade.

In marked contrast to the effect produced by hydrophobia, tarantism appeared to evoke in its victims an intense longing for the sea, into which at times they would precipitate themselves; at all times they seemed to prefer the vicinity of water, sometimes carrying globes of this fluid whilst dancing.

In its origin tarantism appears to have been contemporaneous with the St Vitus’s dance of Germany. It first appeared towards the end of the 14th century in Apulia; theuce it spread gradually throughout Italy, and reached its height during the 17th century, by which time the dancing manias of the North had already died out. It affected not only inhabitants of the country but foreigners visiting it; age appears to have had no saving influence: children and old people alike commenced dancing at the sound of the tarantella, but as a rule women were more susceptible than men. From the 17th century onwards it has gradually declined, and is now practically unknown, the only relic of it being the graceful dance of southern Italy called the tarantella. The bite of the tarantula is painful but not dangerous, and the real cause of the phenomena described above must be sought in the temporary ej>idemic prevalence of an hysterical condition.

The Lycοsα tarantula is figured in Ann. Sc. Nat., 2d ser., iii. Zoologie, 1835.

The town wakes up for the fair of Beaucaire and the fête of La Tarasque, the latter in celebration of St Martha’s deliverance of the town from a legendary monster of that name. King René presided in 1469, and grand exhibitions of costume and strange ceremonies take place during the two days of the festival. Tarascon was originally a settlement of the Massaliots, built on an island of the Rhone. The mediaeval castle, where Pope Urban II. lived in 1096, was built on the ruins of a Roman castrum. The inhabitants of Tarascon preserved the municipal institutions granted them by thé Romans, and of the absolute power claimed by the counts of Provence they only recognized the rights of sovereignty. Tarascon played a bloody part in the White Terror of 1815.

The roots of other Composite plants are sometimes gathered by careless collectors for dandelion, especially that of Leοηtοdοη hispidus (L.). The root of this plant is tough when fresh, and rarely exudes any milky juice. The flowers, moreover, have feathery pappus, while in the dandelion it is simple.