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in diameter, can support a weight of 244 kilogrammes, or BOOK 500 pounds, without breaking. As gold is very soft, it must be mixed with copper, when coined into money. This alloy gives it a reddish tinge. Gold acquires a resinous electricity.*

Native silver is rarely found pure in the bosom of the Silver. earth; it is sometimes mixed with copper and iron, and sometimes with gold, but more frequently with arsenic. The same province of South America which possesses the richest gold mines, namely, Peru, contains also great treasures of silver.

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The mines of Potosi produced, from the year 1545 to Geographi1648, about 395,619,000 piastres, but they are exhausted. sion of this In North America, Mexico abounds in silver, about 22 mil- metal. lions of piastres being derived from it every year.† Silver is apparently diffused throughout the whole extent of the old continent; but the mines which are now best known, are almost all found in the temperate zone of the North. Those of Siberia, of Saxony, and of Hartz are at the 50th degree of latitude-those of Konigsberg in Norway, at the 60th degree. The produce of these mines, however, is trifling, compared to the mineral riches of America, which are contained within the two parallels, distant thirty degrees from the equator. We are ignorant whether Africa. possesses mines of silver equal to those of the New World.

tion.

Silver is found in quartz, limestone, sulphurated zinc, Its posi and sometimes in petrosilex ; it is rarely met with in granite rocks. At Frankenberg, in Hesse, leaves of native silver are found adhering to petrifactions. This metal exists in grains (though rarely) in a thread-like form, in thin laminæ, in ramifications, in octahedral crystals, and sometimes in very considerable masses. We are assured, that one was found at Schneeberg, in Saxony, in 1748, which

* Haüy, Annales du Muséum. iii. 309. sqq.

+ Humboldt, Essai Politique sur la Nouvelle Espagne.

‡ Bergmann, Géographie Physique, i. 266.

Werner, Nouvelle Théorie des Filons, 79 et 79.

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BOOK weighed 400 quintals, or 196 kilogrammes.* Another mass was found at Konigsberg, of the weight of 560 marks, (about 270 kilogrammes.) and is preserved in the Royal Museum at Copenhagen. Bergmann says, that there has been found in the sands, upon the coasts of Peru, masses of 150 marks of silver entirely pure.

Quality

of silver.

Silver is, next to gold and platina, the most unalterable of the metals-its surface only blackens in those places where there are sulphureous and inflammable vapours. It is remarkable that silver, alloyed with a considerable portion of gold or copper, preserves its white colour; whilst a small quantity of silver or copper, mixed with gold, changes very sensibly the colour of this latter metal. This phenomenon, common to all white metals, made Newton imagine that the particles of white metals have much more surface than those of yellow metals, and that they are even very opaque; so that they cover the gold and copper, without permitting the colour of these metals to pierce through theirs. They ought, on the other hand, to be more thin, because the white light which they reflect, answers to a greater degree of tenacity, than the yellow of gold or copper. According to the experiments of Brisson, and the calculations of Haüy, the specific gravity of a mixture of gold and copper, exceeds the sum of the specific gravities of the two metals when separate about. On the contrary, the specific gravity of a mixture of silver and copper, is less than the total of the specific gravities of the two metals, by about. Another physical quality of silyer is still more worthy of our attention, the property which it has, when dissolved in nitric acid, of crystallizing under a kind of vegetable or arborescent form, producing what is called the tree of Diana. It would seem, that the crystals of which this kind of mineral vegetation is composed, may be considered as small magnetic rods, whose poles, by attracting and repelling each other, determine

*Hauy Mineralogie, vol. iii. p. 388. note 2.

+ Newton, Optice Lucis, lib. ii. part 3. proposit. 7.
Haiy, Minéralogic, tom. iii. p. 380 et 390.

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their respective positions.* Silver, though less rare than BOOK gold, has been preferred to that metal, as a representative of value; the resistances which it opposes to the action of the air and humidity; its brilliant whiteness, and its malleability, render it applicable to a multiplicity of purposes both useful and ornamental, which are too well known to require enumeration.

ed silver.

Sulphate of silver, that is, silver combined with about Sulphuretof sulphur, commonly bears the absurd name of (mine d'argent vitreuse) vitreous silver, though it has not even the exterior appearance of glass. Antimonial sulphureted silver is commonly called red silver, and the fine lively red, which is the essential colour of it, justifies the name. The transparent crystals of this metal form not a bad imitation of the ruby; the more beautiful they are the less silver they contain.

Native mercury is generally found in brilliant and move- Mercury. able globules, disseminated in the clayey schist, as at Idria in Friuli, or rather in Carniolia; in marl, in quartz, as in the district of Deux Ponts, and in primitive lime-stone, as at Almaden in Spain. This metal requires so little heat for its fusion, that the atmosphere always contains enough to preserve it in the fluid state. The cold of Siberia, however, and of Northern Russia, sometimes converts it into the solid form, which has been erroneously considered as congelation, it is then almost as malleable as tin,† and ad- Its congemits of being extended into very thin sheets: besides, its lation. oxide repasses to a metallic state, without the intervention of any foreign substance. It possesses, then, the essential qualities of metals, and approaches the nature of those that are the most perfect. Mercury amalgamates with almost all metallic substances, but chiefly with gold, silver, tin, and bismuth; it is this property, joined to the facility

Ritter, Mémoires sur le Galvanisme, i. cah. 2. p. 280.

+ Bergmann, Géog. Phys. i. 227. Comp. Hachette et Hassenfratz, dans le Journal de l'Ecole Polytechnique, i. cah. p. 123. et suiv.

Braun. Comment. Petrop. novi. xi. p. 268. Blagden, Philosoph. Transact 1783. vol. lxxiii. p. 329.

Gellert. Principes de Chimie Docimastique, 152, (en All.)

[blocks in formation]

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BOOK with which it evaporates, that causes it to be employed in gilding, and in working mines of gold and silver. The silvering of glass is effected by amalgam of mercury and tin. Philosophers make use of the same amalgam to spread upon the rubbers of electric machines. The efficacy of medicines formed of oxides of mercury, is entirely owing to the facility with which these oxides are decomposed by parting with their oxygen. All these physical and chemical qualities shew what an important part mercury would act in the formation of our earth, if it there existed in great Geographi- quantities. At present, this metal is found only in very small portions, and at great distances-it seems to fail in countries in the vicinity of the arctic pole. The whole of Siberia presents to us only two or three ambiguous specimens. The New Continent is not more abundantly provided with it. The natural amalgam of mercury and silver, is called silvery mercury. It remains for us only to notice the sulphuret of mercury, well known under the name of cinCinnabar. nabar, or vermilion cinnabar, and which is sometimes found in regular veins.

cal situation of mercury.

Lead.

An ignoble metal claims the rank next to mercury, that is, lead, a substance of very dense structure, but extremely deficient in point of hardness, elasticity, and even ductility. It is, however, of great utility in its metallic state; conduit pipes, balls for guns, and other plain and coarse implements are made of it; and the oxides of lead are employed in many of the arts. It is lead which gives to glass an unctuosity which renders it susceptible of being easily cut and polished. It is to lead, or to its red oxide, that glass, called flint glass, owes the quality which renders it so valuable for the construction of the object glasses of achromatic telescopes,-the quality of divesting the images of those colours, with which they appear to be edged when we view them through a common telescope. The oxides of lead furnish a variety of colours both to the pallet of the painter, and the toilet of the modern Laïs.

Georgi, Description de la Russie, iii, 406.

Position of

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This metal is generally found mineralized by sulphur, BOOK forming an ore commonly called galêna, which is almost X. always mixed with iron, with antimony, and especially with silver. This ore is generally worked only for the purpose lead. of extracting from it the silver it contains. Werner specifies seventeen formations of galena of different periods, in all sorts of rocks, from the quartz to pit-coal.* There are no kind of mines more common in Europe. The kind of galena which contains silver, is met with in Danish Laponia. But lead is not found in abundance, any here in the GeographiNorth of Europe, or Asia. It begins to discover itself in sion. great quantities, only in Germany, France and England. We are assured that in the interior of Louisiana, it forms vast beds upon the surface. Carbonate of lead, or mineral white lead, often accompanies galêna; it is an oxide mineralized by carbonic acid. Molybdate of lead, or the oxide mineralized by molybdic acid, is found at Bleyberg in Carinthia; it generally bears the name of yellow lead. The red lead of Berezof in Siberia is mineralized by the chronic acid. It is still doubtful whether there exists any lead in the native state.

Nickel is not a very ductile metal; it is of no use in the Nickel. arts, but it possesses some magnetic properties. It generally accompanies cobalt, an equally magnetic substance; these two metals, of a nature nearly allied to that of iron, and often containing particles of it, seem to occur most plentifully in the north.

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Copper, one of the metals of which nature is most lavish, Copper; its appears to occupy two great regions of the globe which ad- geographimit of being distinctly defined. We know that it abounds in sion. Norway, in Sweden, in Hungary, in England, in the Uralian mountains, throughout all Siberia, in Chinese Tartary, and Japan. We must also add, that several islands between Kamstchatka and America produce masses of native cop

*Werner, Théorie des Filons, p. 156-161 (en All.)

† See Description de la Louisiane.

Expériences des Biot, cité dans le Tableaux des Espèces Minéral de Lucas, p. 297. Comp. Hauy, Minérals, iii. 512.

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