BOOK parency by exposure to the air. IX. Position of mica. Another variety of mica in spangles of a yellowish gold, or whitish silver colour, is known all over the world, by the ridiculous names of cat's gold, or cat's silver. The gilt sand, and gold powder, which the paper-makers use for purposes of ornament, are only mica in small fragments. Mica, says Dolomieu,* belongs essentially to the primordial rocks, where it has originated in the midst of the confused crystallization by which these rocks have been formed. That which is imbedded in certain stony substances, of secondary formation, has been conveyed thither after the destruction of the rocks which inclosed it; and so much the more easily, as its particles, thin and light, were susceptible of being carried along by the waters, which deposited them with other sediments of an analogous nature. The remains of mica, are also found (having been carried thither) in the beds of hard grey-stone. (grès) and schist, which generally alternate with strata of coal. Its fragments are still often disseminated in the sands of the most recent epoch; thus it exists in different states in substances of every formation. It appears that, in the south of Europe, as has been well observed by Dolomieu, mica is rarely found crystallized by itself; that in rocks it does not form lamina of any sensible extent, and that, even in the state of veins, its plates are only some inches in dimensions; but all accounts agree in asserting that it is found in Russia, Siberia, and Songoria, in laminæ, and in masses, sometimes more than two ells square. It is in the granite mountains near the rivers of Maina and Aldon that the mica is worked. It is found in detached masses, and it sometimes appears on the surface of the earth, but is oftener covered with a bed of talc.t Near the lake Baïkal, and in the Uralian mountains, we meet with masses composed of rhomboidal and hexagonal laminæ of transparent mica in the midst of granite. It is * Haüy, Minéralogie, iii. 214. Gmelin, dans Georgi, iii, 238. an undoubted phenomenon in physical geography, that the BOOK most abundant crystallization of mica is in the northern regions. IX. Talc, which differs from mica by the greasiness of its Talc. surface, is also less hard; it does not even mark the carbonate of lime; it is easily scraped with a knife. On the other hand, it differs from soapy clay, because it forms no paste with water, and does not adhere to the tongue. The talc of Venice, which abounds in the Tyrol and Valteline, is of a greenish white, silvery, and divisible into thin, transparent, and flexible plates; it furnishes a powder which renders the skin smooth, and is employed as a cosmetic. The scaly talc is known under the name of chalk of Briançon. Steatite, or Rock Soap, is the graphic talc of Haüy. It is the substance of which these little figures that are brought from China are formed, and whose grotesque appearance has caused them to be called Magots, in allusion to a species of monkey which bears that name. The "talc ollaire," which is easily turned on the wheel, is made into pots. This substance belongs equally to the primitive and se- Position condary rocks, but it is less common in the latter. Accord- of talc. ing to Dolomieu, it sometimes arises from the decomposition of serpentine rocks, and it then occupies cavities where the products of the decomposition are collected. Dolomieu, however, considers the talc as formed a long time after the granite rocks. It indeed is disposed in very extensive banks, but then it is neither pure nor homogeneous. The purest talc is found in detached nodules imbedded in micaceous rocks. The open chlorite talc, seems sometimes to have penetrated by filtration into the veins of the primitive rocks; it is coloured by iron. In Corsica, and near the White Sea, we find a foliated sort, which is penetrated throughout with little sparkling crystals of iron. The green earth of Verona, which is used in painting, is a variety of chlorite * Talc, a stone greasy to the touch and sight; from talg, fal, in Danish, Swedish, German. BOOK talc; it is contained in beds of compact lava, into the cavities of which it has been introduced by filtration. IX. Tourmaline. We shall be obliged to pass rapidly over many interesting species, such as the tourmaline or the electric schorl, which is remarkable for its very strong electricity in its two opposite points; when heated, it attracts or repels light boLazulite. dies, such as ashes;*—the lazulite, or sapphire of the ancients, which furnishes the superb paint called Ultra-marine, the permanency of which, by the side of the other colours, which are more or less affected and altered by the action of the air, somewhat impairs that harmony of tints which is so pleasing in pictures;-a number of stones, to which the names have successfully been given, of zeolite, jade, or nephrite, which resembles talc; idocrase, otherwise vesuvian; the amphigene of Haüy, otherwise the leucite or white garnet; the emeraudine, (dioptaze of Haüy,) which, by its beautiful green colour, derived from copper, indicates the emerald species; and a number of others, which it were tedious to enumerate. We will terminate this hasty survey of earthy substances by a brief description of the celebrated asbestos. Jade. Asbestos, thus. This substance, called also amianthus, appears to be proor amian- duced from the decomposition of primitive rocks, amongst which it is oftenest found. It chiefly occupies fissures and cavities of steatitic rocks, serpentine, and others abounding in magnesia. The asbestos which is found in the mountains of Tarantaise, in Savoy, forms silky filaments of more than three decimetres, or about a foot in length. People, when they see, for the first time, a detached tuft of asbestos, can scarcely be convinced that it is actually a stone, and not a species of fine white silk. Asbestos abounds in Corsica; Dolomieu made use of it, instead of hay and tow, to pack up other minerals. Ciampini says, that the longest asbestos *Minéralogie de Hauy, iii. pages 44-58. + Bayer, Dissert. de Sapphiro. Beckmann, Histoire des Inventions, iii, 182. IX. Use of the he ever saw came from the Pyrenees.* It abounds in the BOOK Uralian mountains, and in Greenland. In Corsica, they mix asbestos with the clay used in the potteries, which is thus rendered less brittle, and more capable of resisting the asbestos. sudden alterations of heat and cold. The ancients spun the asbestos, and made towels, napkins, and head dresses of it. When these became soiled by use, they were thrown into the fire, which did not destroy the substance of the asbestos, and upon being taken out, were found to be whiter than if they had been washed. In the funeral obsequies of kings and emperors, the dead body was enveloped with cloths of asbestos, before it was placed on the funeral pile; and thus the ashes were obtained quite unmixed. In modern times, the Russians alone have attempted, but without success, to spin the asbestos. The inhabitants of the Uralian mountains have still preserved some remains of this frivolous industry. The indestructible paper, made from this substance, appears more useful. Wicks for lamps are also formed of all the asbestos, which easily imbibe oil, and burn with a brilliant flame. Father Kircher made use of such a wick for more than two years, without any perceptible decay, but, having wet it by accident, was prevented from continuing his experiment. Perhaps the fabulous accounts. of unextinguishable sepulchral lamps derive their origin from this circumstance. Of the inflammable substances, sulphur naturally presents Sulphur. itself first to our observation. That which is crystallized by the action of a liquid, is found in veins or in beds, amongst sulphate of lime, or amongst potters clay. These beds, which are often very extensive, border upon strata of rock salt. Crystals of sulphur sometimes adorn the interior of calcareous, or even quartz eagle stones. With respect to sulphur formed by sublimation, it is found in powder, in striated masses, or even in crystals, at the mouth * De Lino Incombustibile; Romæ, in 4to. 1691, p. 5, 6. + Pliny, Nat. Hist. b. 19. ch. 1. Bruckmann, Magnalia Dei in locis subterr. ii. 955. Georgi, iii. 241, Egede, Account of Greenland, (in Danish.) 212 IX. BOOK of many volcanos, such as Etna, Vesuvius, and Mount Hecla. Sulphur is also obtained from the putrefaction of animal matter. Several substances, amongst others the sulphurous pyrites, are impregnated with sulphur. We cannot doubt that sulphurous and sulphuric acid exerted a powerful agency in the primitive fermentation of the elements-but there is nothing in the existing economy of nature which can enable us to penetrate these mysteries of "chaos and ancient night." Carbon. We have already spoken of the diamond, to which the rigid justice of modern chemistry assigns a place amongst Anthracite. combustible substances. The anthracite, a substance similar to the pit coal, combined with stony matter, of difficult combustion, appears to have the same principle for its basis as the diamond, namely, pure carbon, accidentally mixed with flint and iron. The anthracite occurs chiefly, but not exclusively, in primitive rocks, where it forms considerable masses. Thus, as Dolomieu observes,† "carbon, or the carbonaceous principle, exists in nature, independently of animals and vegetables, of which there are no traces found in the primitive soils." Let us also add, that sulphur must have existed before organized bodies, since, as Delamétherie Deluc has lately exobserves, it is found in granite.+ pressed the same opinion in relation to primitive calcareous earth. We seem every day becoming more disposed to admit the formal pre-existence of all the elements which enter into the composition of the globe, whilst false logic would represent them as being wholly the remains of animals or vegetables. Let us rather say, that the organic energy of nature exerted in two different directions, has given rise on one side to calcareous rocks, alkaline-earthy substances, and animals-on the other, to quartzeous and bituminous substances, and vegetables; constantly putting in action the same elements, or their * Hericart de Thury; quoted by Brongniart, Tr. de Minéral, ii. 58. Théorie de la Terre, ii. p. 250. Journal de Phys. 1803, |