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pally derived from the horn silver. brittle silver, vitreous silver, and arsennuretted ores, as also, to a certain extent, from the native ores. The ores of Mexico are of a similar character.
In Mexico, the mines are most abundant in the back of the Cordilleras, between 18 and 24° north latitude. In Peru, the principal mines are in the districts of Pasco, Chota, and Huantaga.
The celebrated Potosi mines, in Buenos Ayres, occur in a mountain of argillaceous shale, whose summit is covered with a bed of porphyry. The ore is red silver, vitreous ore, and native silver.
In Europe, the principal mines are those of Spain, Norway, Saxony, Austria, and Russia. The silver of Spain is chiefly obtained from galena, and principally in the Sierra Almagrera, in Grenada.
In the 'Tyrol, the sulphuret of silver, argentiferous, grey copper, and misnickel, occurs in a gangue of quartz in argillaceous schist.
The Hungarian mines at Schemnitz and Kremnitz are in sycnnite and hornblende porphyry, in a gangue of quartz, often associated with cale spar of sulphate of barytes.
The Russian mines of Kolyvan, in the Davuria mountains, Siberia, are steadily increasing in value, and annually produce about 47,800 pounds of pure silver.
The common methods of reducing silver ore in the large way are two— by smelting and by amalgamation. When argentiferous galena in the mineral is operated upon, it is treated in a reverberatory furnace as an ordinary lead ore. To separate the silver from the lead, it is fused in the same kind of furnace. of which the hearth is composed of bone ash. A current of air is also admitted through a tuyere on one side of the appa ratus, which, passing constantly over the surface of the fused metal, oxidizes it and converts it into litharge, which escapes through a proper channel prepared for that purpose. At the end of a certain time the whole of the lead is thus removed, and the silver remains in a state of almost perfect purity. The completion of the process is known by the metal becoming brilliant, and, on cooling, throwing out arborescent sprouts, resembling the branches of some kinds of coral.
According to Pattinson's new method, (now very generally adopted,) the silver is separated by melting the lead in large iron pans, and, as it begins to cool, straining out the crystal with a perforated iron ladle. From the greater fusibility of the alloy of lead and silver, the portion left behind contains nearly all the latter metal. This process being repeated several times in the same portion of alloy, it ultimately becomes very rich; and, when it contains from 300 to 400 ounces of silver to a ton of lead, it is exposed to a bone ash test.
Very beautiful models of a refining furnace, and a set of crystallizing pots, were exhibited by the Duke of Buccleugh. In their immediate vicinity was seen a drawing, together with a series of products, inclu ding a large plate of silver, by which Mr. Pattinson illustrated his process of enriching lead by crystallization. When amalgamation by mercury is employed, the silver ore is brought to a state of chloride by a mix ure of the powdered ore with about 10 per cent. of common salt; the chloride formed is reduced by means of sulphuret of iron, or by iron filings, and, at the same time, the liberated silver combines with the mercury which has been added to the mixture. The amalgam, separated from the muddy mass by a current of water, or washing, is then filtered from the
excess of mercury, and, as a last step, is subjected to a strong heat in a distilling furnace, by which the silver is left behind, whilst the mercury passes off in the form of vapor, to be condensed in a large receiver, partially filled with water.
There were many rich specimens of argentiferous galena and other silver ores exhibited. Among the most remarkable of these were a large mass of native silver from Chili, and some very beautiful specimens of the same substance from Prince's Location, Lake Superior.
Mercury. This metal occurs in the native state, alloyed with silver, and in combination with sulphur, chlorine, or iodine. Native mercury is rarely found, yet it is met with in greater or less quantities in various mines of that metal.
Cinnabar, the native sulphuret of mercury, is a dullish mineral of a reddish-brown or brownish-black color, and, when scratched, affords a red streak: when pure, it consists of 86.29 parts of mercury, and 13.71 parts of sulphur. This mineral, from which the principal part of the mercury of commerce is obtained, mostly occurs in connexion with talcose and argillaceous shales, but has also been sparingly found in granite. The principal mines are at Idria, in Austria; Almaden, in Spain; in the Palatinate, on the Rhine; and at Huanca Velica, in Peru. Mercury also occurs in Mexico, Hungary, Sweden, France, and Tuscany. Chloride of mercury, which is a tough, sectile ore, of a grey or yellowish color, is an extremely rare mineral, and does not occur in sufficient quantity to be metallurgically treated for the quicksilver which it contains.
The mines of Idria were discovered in the year 1497. The ore is obtained at the depth of 750 feet from the surface, and is mostly a bitumin ous cinnabar, disseminated through the well along with native mercury. In some parts of the vein this is so abundant, that when earthy rock is newly broken, large metallic globules flow out, and fall to the bottom of the gallery. After the native mercury has been separated by filtration, through a sieve, the mineral and its adhering gangue is washed and prepared for reduction. For this purpose a large circular building, 40 feet in diameter and 60 feet in height, is employed, which communicates, through numerous small openings, with a range of chambers disposed on either side The building in the centre of the arrangement is filled with earthern pans, containing the prepared earth, and the whole is afterwards closed up, and the heat is gradually applied. The mercury sublimes and is condensed by the cold air of the smaller chambers, whence it is subsequently removed and packed into iron bottles. The mineral produce of these mines amounts to about 150 tons per annum.
The mines of the Palatinate, on the Rhine, and those of other parts of Germany, are said to yield 7,600 quintals per annum. Those of Almaden, situated near the frontier of Estremadura, in Spain, have been worked from remote antiquity without sensibly diminishing the yield. According to Pliny, they were worked by the Greeks seven hundred years before our era.
The mines at Huanca Velica, in Peru, have afforded a large amount of mercury for amalgamation at the Peruvian silver mines. Between the years 1590 and 1800, they are estimated to have produced 537,000 tons. Their present annual yield amounts to about 1,800 quintals.
The Chinese are stated to have mines in Sheusia, where the ore is reduced by the rude process of burning brushwood in rocks or pits dug out for that purpose, and then collecting the metal after condensation.
Few ores of mercury occur in Great Britain. In the foreign part of the building were several illustrations of the metallurgy of this important mineral. The inspector of mines of the district of Almeria, besides contributing various other minerals, sent some fine specimens of cinnabar. From the imperial mines of Vienna there were specimens of mercury and cinnabar, as well as samples of the same products from the mines of Idria.
Platinum. This metal is usually found combined with more or less of the rare metals-palladium, rhodium, iridium, and osmium, besides variable quantities of copper and iron. It commonly occurs in flattened grains, and in angular, irregular masses, and was first detected in alluvial deposits in South America, whence it derived its name of platina, a diminutive of the word plata-meaning silver. It was discovered by Ulloa, a Spanish traveller in America, in the year 1735, and was made known in Europe in 1748. It has since that time been found in the Urals, in Borneo, in the sands of the Rhine, in St Domingo, and in our own country. The Ural districts afford the chief portion of the platinum of commerce. It occurs there, as elsewhere, in alluvial beds; but the course of the platiniferous alluvium has been traced for a considerable distance up the mountains, consisting of crystalline rock, the evident origin of the detritus. From one to three pounds of platinum are procured from two tons of sand.
The infusibility of platinum, and its resistance to the action of air and water, and of most other agents, natural or chemical, render it of great value in the construction of chemical and philosophical apparatus. The large vessels employed in the manufacture of sulphuric acid are now made of platinum, which is entirely unaffected by this corrosive substance. It is also employed for crucibles and capsules, used in chemical analysis, for galvanic batteries, and it is worked into foil, drawn into wire, or fashioned into cups, which hold bodies heated in the blow pipe. It alloys readily with silver, lead, and several of the other metals, and it is also attacked by caustic potash and phosphoric acid, in contact with carbon; consequently, care must be taken, when treating it, that it be not exposed to the action of any of these substances. For many years after its discovery, platinum was, on account of the difficulty of obtaining it in masses, an almost useless metal. When strongly treated, the grains are readily welded together; but, from the smallness of the fragments, this causes interminable labor, and besides does not afford a pure metal. The process now generally adopted was first introduced by Dr. Wollaston, and consists in dissolving the native metal in hydrochloric acid, and then throwing down from the solution all orange-colored precipitate by means of muriate of ammonia. This precipitate, which is a double chloride of platinum and ammonia, is then heated and reduced to the metallic state, the platinum being then in an extreme minute state of division. This black powder, which is spongy platinum, is next compressed in steel moulds by the aid of heat and strong pressure, and when sufficiently compact, is forged under a hammer, by which it is ultimately reduced to a solid mass.
Among the illustrations of this metal were some admirably finished dishes and crucibles, exhibited by W. P. Johnson, of Hatton Garden, London; crude and manufactured platinum, by Wolf & Erbslok, Bremen; and a large platinum still, with sundry other articles from the same metal, in the French department.
Malachite. This ore, called the green carbonate of copper, is remarkable for its fine emerald green color, of which the same specimen often exhibits a great variety of shades. It is sometimes found in a crystallized form, but more often occurs in radiated concretions and manipulated uniform masses, made up of several successive layers, of which the extent and thickness are readily apparent.
Malachite occurs in large quantities in the Ural mountains, and in the mines of Australia; in Cornwall, at Chessy, and at other places; and from its high per-centage of metal it is highly prized as an ore of copper, although such varieties as are sufficiently compact are more valuable for the purpose of being polished for ornament-such as snuff-boxes, broaches, or larger objects.
Russia exhibited in her department of the Exhibition the most wonderful works in malachite that have ever been known. The vases, fireplaces, tables, side-boards, and stands made from this article, brought to its highest polish, attracted universal admiration. The ore, in the manufacture, is first sawed into slabs of three-quarters of an inch in thickness, which are ground and polished. These slabs, seldom of a size exceeding three inches in diameter, are then assorted with reference to similarity of color and the running direction of their veins. This done, the workmen then take the model to be veneered, and, arranging the pieces of ore to as near a match as possible, proceed to connect them to each other, and to the frame work which they are to cover. The chief skill of the work consists in an accurate adjustment of one piece with another, so that vein shall meet vein, and color color, in so perfect a manner, that the whole, when completed, may appear as one stone. In the doors of malachite, which were the largest and most costly productions of that material ever manufactured, the adjustment of the different pieces of metal had been accomplished in a manner so perfect that it was difficult to detect the lines of junction. Including bases and capitals, the whole height of these doors was twenty-three feet; their whole width, including mouldings, sixteen and a half feet. They had been first framed of solid oak, and then covered with a coating of brass. The malachite veneering was then cemented upon them, the mouldings being made of the solid ore. After the whole work had been completed, the process of polishing was commenced, and it is, perhaps, the best evidence of the inutility of the metal to any purposes but those of the highest luxury, that the workmen were engaged for three months in perfecting this finishing process. The cost of these doors was stated to have been £8,000 sterling.
Perhaps the strongest impression made upon the mind of the intelligent observer, in his daily walks among the different nations represented in the Exhibition, was that derived from contrast. No better opportunity was ever afforded to learn how much of the improvement in the arts among mankind has arisen from a knowledge of the physical and chemical character of the materials employed in workmanship than was found here. The department of Sheffield, for example, where the highest perfection to which iron, as nature yields it, has been brought, was but a minute's walk from that of Tunis, in which gold, precious stones, and
elaborate carving were lavished upon utensils of the rudest construction. In the one case, inductive science had been long employed to give purity to the material used before it entered the workshops of the artificer; in the other, the vain struggling of rude minds to obtain a conquest over nature, was shown in the unchanged forms of the first combinations of the metal. The keen blade of the penknife or the razor, when compared with the Tunisian sabre, but little in advance (in material used) over the rude arrow-head of the North American Indian, furnished a striking example of what intellectual progress has accomplished for human industry.
With iron, as a metal, every one is familiar. As it is the most useful, so it is, of all the metals, that with which mankind are best acquainted. And yet, even while it is more extensively employed for the supply of human wants than all the other metallic productions of the earth, and while it has been made the subject of scientific investigation from the earliest ages, we are still ignorant of some of its most remarkable properties. Iron, hammered into shape from the pig metal under the intense heat of the forge, becomes fibrous, tough, and susceptible of being bent into almost any shape without breaking or cracking; and yet this same iron, placed as shafting in the cotton or woollen mill, where, in its constant revolution, it shall be subjected to continual jar, or made into the axletree of a railway carriage, and used upon the road, becomes so crystalline and short that it is easily broken, like stove castings, under the blow of the hammer. How many causes, besides vibration, go to pro. duce this change in the structural arrangement of the particles of iron we do not know. The process of cooling iron of the highest quality, undoubtedly has great effect upon its condition, and sometimes renders it valueless as wrought iron. The continued hammering upon the anvil will produce also similar results.
The processes of converting pig into bar iron adopted in England, although bearing much resemblance to those in our own country, have still some points of difference, which cannot be without their importance. The machines adopted for forging and condensing wrought iron vary in form and in principle according to the ideas of the iron-master. The tilt hammer is most commonly employed. The steam-hammer is, however, increasing in use. The blooms are brought under the hammer at a red heat, and beaten out into bars, at the rate of from 70 to 140 blows per minute, the force of the blow being according to the space described by the hammer. The old notion, that rollers would produce as good iron as the hammer, is now generally exploded. The extraneous portions of the metal are driven off by repeated blows; while under the rollers, they are mainly incorporated with the metal.
Railroad bars, of which great numbers were exhibited, may perhaps be regarded as a fair sample of the good bar-iron of England. Coarse, porous iron, of which more than three quarters of the products of the English forges consist, does not make good bars; and hence the necessity of constant selection from the mass produced. Many bars were exhibited broken, for the purpose of showing their molecular structure, and to impress the importance of a tough and fibrous material.
The subject of mixing various qualities of iron together, and of mixing other metals with iron, has received of late much consideration. A pro cess has recently been patented in Great Britain by which cast iron and wrought iron are associated, producing, it is said, a tougher metal. A