that the ancients gathered their gold in dust, and scales, and pellets; and it is still from such deposits in the Urals, California, Australia, New Zealand, and other regions, that the great commercial supply of the metal is obtained. It is not till the drifts get exhausted, or in districts where stream-working is not remunerative, that the auriferous veins are attacked; though, generally speaking, where the vein is a fair one, it forms the steadiest and most reliable source of supply. What are termed "gold ores" are not ores in the strict sense of the term; for whether native amalgams or ores of other metals, the gold they contain, as may be seen by referring to the next section, is still in the free and uncombined metallic condition. According to the present state of our knowledge, the metal is always native, whether occurring in veins of quartz, calc-spar, and baryta, disseminated through the older schistose rocks, incorporated with other ores, or scattered abroad in drifts of sand and gravel.* While gold occurs notably in the drifts of the Urals, Brazils, California, Nevada, Colorado, British Columbia, Australia, and New Zealand, it is also found in minor quantities along the river-courses of many other regions—India, Africa, the United States, and Southern Europe and very sparingly in our own islands, as in Wicklow, Devon, Wales, and the Scottish Highlands. It is mined in Brazil, Central America, Mexico, California, Australia, Spain, Hungary, Transylvania, the Urals, Altai Mountains, and in Sweden; but attempts at mining in Britain (Devon and Wales) have hitherto proved unremunerative. The metallurgical processes for the reduction and refining of gold lie beyond our province; but whether by washing and smelting, by amalgamation with mercury, by treatment with alkalies or other modes of liquation, some of them require considerable chemical skill and nicety of manipulation. The statistics of gold are very imperfect, and in most cases * With regard to the occurrence of gold, the following remarks by P. B. Smyth, Secretary of Mines for the Colony of Victoria, may be of use to the geological student: "Gold is now found to occur not only in quartz-veins and the alluvial deposits derived from these and the surrounding rocks, but also in the claystone itself; and, contrary to expectation, flat bands of auriferous quartz have been discovered in dykes of diorite, which intersect the upper Silurian or lower Devonian rocks. Quartz of extraordinary richness has been obtained from these bands, and the new experience of the miner is leading him to look for gold in places hitherto entirely neglected. It is probable that some time may be lost, and that his labours may not always be well directed or successful, but it is commendable that he should not be deterred from explorations by warnings and remonstrances founded on surmises often baseless. If he had already followed the older precepts, we should at this moment have been dependent for our yield of gold on the shallower alluviums, and the surface only of the veins of quartz." little better than guesswork. Not only does the quantity raised in any given locality vary from year to year, but new localities are unreported, and the success of mining adventures is often either kept secret, or exaggerated for speculative purposes. Roughly estimated, the total yield of the world may be set down at 460,000 lb. troy, representing an approximate value of £23,000,000. The uses and applications of gold in the arts and industries are innumerable. It is employed for coinage, for domestic and personal ornaments, for the formation of alloys, for the preparation of pigments, and for gilding of other metals, wood, plaster, and paper-hangings, and for the preparation of wire and leaf in all their multifarious applications. The extension of its use is generally the test of a nation's wealth, and year after year it is more and more employed in the fabrication of articles of luxury and ornament. Platinum. The metal Platinum or Platina, discovered in 1741 in the mines of Peru, and so named by the Spaniards in allusion to its silvery colour-platina, the diminutive form of plata, silver -is found only in a native or metallic state. What is termed "platinum ore," or crude platinum, is merely an admixture with other metals, such as palladium, rhodium, osmium, iridium, titanium, gold, silver, iron, and copper. Since its discovery in Peru it has been found in Brazil, California, the Urals, Borneo, and other countries. It is usually obtained from drifts in rounded grains or flattened pellets, of a metallic lustre and white colour. When pure it has very much the colour of silver, but of inferior lustre. It is the heaviest of known metals, its specific gravity after hammering being about 21.5. It is exceedingly ductile, malleable, tenacious, and difficult of fusion, but capable of being welded at a high temperaIt undergoes no change under the combined action of air and moisture, resists the strongest heat of a smith's forge, but can be melted by voltaic electricity, or by the oxyhydrogen blowpipe. It is not acted upon by any of the pure acids, but is dissolved by chlorine and nitro-muriatic acid, and is oxidised at a high temperature by pure potassa and lithia. ture. A metal possessed of such properties is eminently fitted for chemical works and laboratories; hence it is manufactured into crucibles, evaporating dishes, stills for concentrating sulphuric acid, spoons, blowpipe-points, tongs, forceps, wire, and similar articles. It is also used for galvanic apparatus, ornamental work in chains and trinkets, medals, and at one time by the Russian Government for coin. It forms alloys with iridium, with iridium and rhodium, and with gold, which are said to possess properties of resistance superior to the pure metal; and with equal parts of steel it constitutes the best white speculum-alloy known. According to Wagner, the amount of metallic platinum annually produced does not exceed three tons, and of this the greater portion comes from the Urals. Palladium. The metal Palladium (Pallas, the goddess), discovered by Wollaston in 1803, is usually found in very small grains, of a steel-grey colour and fibrous structure, in auriferous and platiniferous sands. Its specific gravity is about 11.5; and in fusibility it stands intermediate between gold and platinum. When native it is alloyed with a little platinum and iridium, or with gold and silver, as in the Porpezite of Peru, which consists, according to Berzelius, of 85.98 gold, 9.85 palladium, and 4.17 silver. It is ductile as well as malleable, and is considerably harder than platinum. It is oxidised and dissolved by nitric acid; but its proper solvent is nitro-hydrochloric acid. It forms alloys, most of which are brittle, with arsenic, iron, bismuth, lead, tin, copper, silver, gold, and platinum; the alloy with nickel is ductile. It is sometimes used for the finely divided scales of mathematical and astronomical instruments; for the smaller chemical weights; and 1 per cent added to steel produces a smoother cutting edge. Silver. The early and well-known metal Silver is found native in the older rocks, in threads and strings, in arborescent moss-like aggregates, and in plates and nuggets often of considerable magnitude. In its native state it often occurs as an alloy with gold, platina, mercury, copper, or arsenic-more frequently, perhaps, with mercury than with any other metal. Two specimens of "native silver" from Allemont, in Dauphiné, yielded respectively to Mr Church's analysis 26.15 and 18.34 of mercury. Being principally obtained from its ores, or from other ores with which it is in intimate union, its nature, properties, and uses will be better considered under the section, "Metallic Ores." Mercury, Copper, Iron, &c. The same may be said of Mercury, Copper, Arsenic, Antimony, and Bismuth, which, though occasionally found native, or as native alloys, yet occur in quantities too unimportant to affect their commercial values. The remark is still more applicable to Iron, Lead, Zinc, and Tin, which are all less or more doubt fully native, and even when found only in fragments interesting to the mineral collector. With regard to native iron, it occurs in two states-1st, meteoric iron, which has fallen from the heavens in stones and masses sometimes of considerable size, and contains nickel along with cobalt and traces of other metals; and 2d, telluric iron, which occurs in minute grains and scales in other mineral veins, and contains carbon, or occasionally some other metal, but not nickel. It is sometimes very difficult, however, to assign an origin to certain masses of iron-as those, for example, discovered by Nordenskiöld in 1870 at Ovifak in Greenland. There, fifteen huge masses of native iron (one of them calculated at eighteen tons) were found within an area of 150 square feet, and apparently associated with a basaltic rock, which also contained many fragments of metallic iron. We say apparently associated, for these detached blocks were partially incrusted with basalt, and the whole evidently owed a common origin. Nordenskiöld and Wohler would assign to these masses an extra-terrestrial origin; while Daubrée and Berthelot are inclined to regard them as products of fusion and eruption from below-the enveloping basalt sometimes containing as much. as twenty per cent of iron oxide. The following are the results of Daubrée's examination :- Iron, metallic, Iron, combined with oxygen, sulphur, and phosphorus, Carbon, free, Nickel, Cobalt, Oxygen, Arsenic, sulphur, phosphorus, silica, copper, water, &c., 0.91 12. 10 8.61 100.00 On the whole, the native metals, with the exception of gold, platinum, silver, and mercury, are of no great commercial importance; and it is almost exclusively from the ores that we derive by ingenious and often difficult processes our main metallic supplies. II. THE METALLIC ORES. As already stated, the great majority of the metals occur in nature, not as free and simple elements, but in combination with other substances, forming what are termed ores. These ores have all, more or less, a stony aspect; but in general their higher specific gravities, their more varied colours, and their metallic lustres, in the fresh fracture, serve generally to distinguish them from ordinary stones. Almost all of them occur in veins traversing the older rock-formations-the clay-band and blackband ironstones, and the copper-slates of the stratified systems being the chief exceptions. They present numerous varieties, and are often very complex in composition-their reduction to the metallic state requiring, in some instances, great chemical skill and expensive manipulation. Mineralogically, they are classed and treated as oxides, sulphides, carbonates, silicates, &c.; and in many respects this arrangement, which has already been given in Chapter II., has much to recommend it. Occasionally they are arranged, according to their metallic bases, as ores of iron, ores of copper, and ores of lead; and these metals, again, treated according to their physical properties of weight, hardness, brittleness, ductility, malleability, and capability of being welded. In metallurgy, this plan has many advantages, as bringing each metal, with its several ores, distinctly and directly under the eye of the inquirer. Industrially, it matters little what plan of arrangement is followed, so long as the geological sources and nature of the ores are described, the peculiarities of the metals explained, and their uses in the arts and manufactures briefly indicated. Adopting this view, we shall take the metals in alphabetical order, as sufficient for economic purposes, and as affording, perhaps, the readiest means of reference. It is true that some of them are unknown in the arts; but even these, in the rapid progress of industry, may yet be utilised, and acquire a commercial value. And economically speaking, there are few substances on which more labour and capital are expended than on the ores and metals-in the mining, the transport, and the reduction of the former, and in the working, fashioning, and myriad applications of the latter. Metallurgy in all its branches is a gigantic art, whether as regards the science and ingenuity displayed, the amount of labour and capital employed, or the value and importance of the substances produced. And gigantic as it seems, it is yearly on the increase, not merely in the amounts produced, but in the adoption of more skilful methods, by which production is cheapened and improved, and substances formerly thrown to the waste-heap utilised and invested with commercial importance. Aluminium. Aluminium, though never found in a free or native state, is extensively diffused in nature in the different compounds of T |