is ground and amalgamated in pans, of which there are numerous forms. The charge for a pan is 800 to 1,500 lbs.; the very large pans, treating tailings which have been already ground fine, can take 3,000 to 4,500 lbs. To maintain a proper temperature, steam is introduced into the pulp or into a steam chamber under the bottom, and a wooden cover is usually kept on the pan. The pulp is generally ground for one or two hours; then the quicksilver is sprinkled in (usually 60 to 70 lbs. to a charge of 1,200 or 1,500 lbs.), and, the mullers being raised to avoid too much grinding, which would "flour" the mercury, stirring is continued for two or three hours longer, after which the pulp is diluted and drawn off into a settler. The modification of the Washoe process invented by Mr. Henry Janin, consisting in the use of large quantities of copper vitriol (blue stone) and salt, has proved very successful in the reduction of refractory ores not otherwise amalgamable. The quicksilver, charged with amalgam, is washed, skimmed, and strained through a canvas bag, which retains the amal gam. This is then distilled in cast-iron retorts, the mercury being collected under water, while the "retort bullion" remains behind. About one sixth of the charge retorted, or 200 lbs. of bullion from 1,200 lbs. of amalgam, is usually obtained from the retort, to be broken up, melted, and cast into ingots; it loses 2 to 3 per cent. in melting. The ingots are assayed, and their fineness in thousandths of gold and silver is stamped upon them. The coin value of the Comstock bullion is $1 75 to $2, one third of which is due to the gold it contains. The pulp escaping from the apparatus in which the amalgam is collected is called "tailings." The tailings are often concentrated upon blankets or otherwise, or are simply allowed to settle in reservoirs, for reworking. The "slimes" or "slums" comprise that part of the ore which is crushed under the stamps to an impalpably fine condition, and escapes in the battery water without ever getting into the pans. Since many silver ores yield much fine powder in crushing, the slimes are often far richer than the tailings, the value of the latter being largely in the particles of quicksilver and amalgam which they contain. The chemistry of the Washoe process is summed up by Mr. Arnold Hague as follows: that the ore submitted to it consists chiefly of native gold, native silver, and argentiferous sulphurets, associated with varying proportions of blende and galena; that the action of sodium chloride and copper sulphate in the pan produces copper chloride, while the presence of metallic iron causes the formation of copper dichloride; that both the chlorides of copper assist in the reduction of the ore by chloridizing the sulphurets of silver and decomposing the sulphurets of lead and zine; that sulphate of copper enhances the amalgamating energy of mercury, by causing the formation of a small quantity of copper amalgam, and also tends to expel the lead; but "raw that the quantities of chemical agents usually added in the Washoe process are too small to be effective, and that the principal agents in the reduction are in general mercury and the iron of the pan, aided by heat and friction. The essential condition in the amalgamation is the keeping of the mercury bright and pure, that it may come into direct contact with the iron and sulphide of silver. The consumption of mercury in the Washoe process may be considered chiefly a mechanical loss, and only to a limited extent a chemical one. The pan amalgamation of slimes and refractory ores, with the addition of large proportions of copper sulphate and salt, involves a greater loss of mercury.-Refractory ores, not suitable for amalgamation by the Washoe or the patio process, are treated in many localities by the Freiberg process, consisting in the chlorination of the ore by roasting with salt, and its subsequent amalgamation. At Freiberg in Saxony, where this method originated, it has been abandoned, the ores formerly amalgamated being now treated by smelting. But in districts where fuel is scarce and labor dear, and lead ores for smelting are not at hand (which is the case in many parts of Nevada, for instance), the Freiberg system is still successfully employed, though greatly modified as to apparatus. The ore is crushed in stamp mills, without water, and the fine powder is further dried, usually by spreading on the top of the arch or the dust chambers of the roasting furnace. Either in the battery, during crushing, or on the drying or the charging floor, 6 to 7 per cent. (for rich ores, up to 20 per cent.) of salt is mixed with the ore. mixture is then roasted, to chloridize the silver; this was done abroad in reverberatory furnaces, which have been used in Colorado and Nevada also, but are now generally replaced in the west by Stetefeldt's showering furnace or Brückner's cylinder. From the roasting furnace the ore is conveyed to the pans, where it undergoes an amalgamation similar to that of the simple Washoe process, except that less grinding is necessary. The Freiberg amalgamation was performed in revolving wooden barrels, which are still employed at some places in the United States. Each apparatus has its partisans. A peculiar method of amalgamation pursued in Chili avoids the chloridizing roasting, substituting a humid chlorination by means of copper dichloride (Kröncke's process). It is highly praised, but not yet widely employed. The use for this purpose of copper chloride, which is of earlier origin, involves a loss of quicksilver as calomel.-The processes of humid extraction of silver are of two classes. Either the silver is converted into a soluble compound and separated by leaching and precipitation, or the baser metallic constituents of the ore are rendered soluble and removed by leaching, leaving an auriferous and argentiferous residuum for further treatment. The methods of the first class convert the silver The COUNTRIES. into chloride or sulphate, the former by a mation of metallic silver, instead of the desired chloridizing, the latter by an oxidizing roast- sulphate. Hence the application of this proing. The chloridizing roasting is essentially cess is limited. Its best field is the treatment that of the Freiberg amalgamation process, of the copper mattes of Mansfeld, containing and is effected by mixing salt with the charge. 70 to 72 per cent. of copper, and 0.33 per cent. The silver chloride is extracted from the mass of silver. The so-called acid extraction is prinby lixiviation with hot brine (old Augustin cipally used upon cupriferous furnace proprocess), cold brine (Hungarian improvement), ducts, which contain too much lead, antimony, sodium hyposulphite (Patera process), or cal- arsenic, &c., to permit treatment by the Aucium hyposulphite (Kiss process in Hungary gustin or the Ziervogel method. In this proand Russia, Hofmann in Mexico). The latter cess, the base metals are dissolved out by extracts also gold chloride if it is present, treatment with sulphuric or muriatic acid, and which brine will not do, unless it has been, as the residuum, containing gold and silver, is Patera recommends, impregnated with free further reduced by smelting, or in rare inchlorine gas. Experiments conducted at Wy- stances by humid methods. For full discusandotte, Mich., by Messrs. Courtis and Hahn, sions of all the foregoing processes, see Percy's indicate the availability of other chlorides than "Metallurgy," and Bruno Kerl's Metallhüttencommon salt (particularly calcium chloride, or kunde. The details of American practice, and a solution obtained by treating common lime- critical comparisons of different American and stone with muriatic acid) as a solvent for the foreign methods, are given in the reports of R. silver chloride. The novel and important re- W. Raymond, United States commissioner of sults of these investigations are given in the mining statistics, and in the "Transactions of "Transactions of the American Institute of the American Institute of Mining Engineers." Mining Engineers." From its hyposulphite-The principal uses of silver have been menor chloride solution the silver is precipitated tioned already in this article; see also COINS, with metallic. copper, as cement silver, which GALVANISM (section on electrotyping), MINT, is washed, pressed, melted, and cast into bars. and PLATED WARE. The real value of silver Ziervogel's method of extracting silver by as compared to gold has varied in different roasting the sulphuretted ore to produce sil- ages from one eighth to less than one sixver sulphate, leaching this with hot acidula- teenth; but the mint rates have often been ted water, and precipitating with copper, is arbitrarily established by government for the the simplest and cheapest of all; but it re- profit of the treasury, in spite of the market quires very skilful and delicate roasting, and price of the metals. At present it is lower ores comparatively free from lead, antimony, than at any previous period. The average arsenic, and zinc. The three latter tend to ratio of value of silver to gold in the London cause volatilization of silver; the sulphide of market for the year ending Dec. 31, 1874, was antimony and lead cause a sintering of the 1 to 16-27. The following table shows the esroasting charge; copper dioxide, or too high a timated product of silver at various temperature in the furnace, leads to the for- in the present century: periods Total Approximate value in U. S. coin 2,337,800 £6,515,925 2,827,425 £8,788,416 $47,443,200 4,017,000 $58,820,000 $36,250,000 $31,537,000 $43,853,000 $42,536,000 $47,443,800 $62,303,000 $58,820,000 by Maria Theresa) is traversed by a group of The following estimate of the world's product | celebrated school of mines, founded in 1760 of silver in 1873 is based upon returns for Germany, Austria, France, Great Britain, Spain, and the United States, and for other countries upon the most recent available accounts: Great Britain and colonies, $1,000,000; Sweden and Norway, $250,000; Russia, $500,000; Austro-Hungarian monarchy, $1,600,000; German empire, $3,000,000; France, $2,000,000; Spain, $2,000,000; Italy (Sardinia), $500,000; Mexico, $20,000,000; Central and South America, $8,000,000; Canada, $900,000; United States, $36,500,000; total, $76,250,000. According to Humboldt and Danson, the value of silver produced in Mexico and Peru from 1492 to 1803 was $4,152,650,000. The production in Europe during the same period was about $200,000,000. For the period from 1804 to 1848 Danson gives $1,244,380,794 as the production of Mexico and South America, that of Europe and Asiatic Russia for the same period having been about $325,000,000. For the period from 1848 to 1868, Prof. W. P. Blake, in his "Report on the Production of the Precious Metals," gives the following estimate of the silver product: United States, $73,000,000; Mexico, $380,000,000; South America, $200,000,000; Australia, $20,000; Europe and Asiatic Russia, $160,380,000; total, $813,400,000. From 1868 to 1875 the product of silver may be approximately estimated at $163,000,000 for the United States, $140,000,000 for Mexico, $56,000,000 for South America, and $63,000,000 for the rest of the world. (None of these estimates include the produce of Japan, China, and central Asia, of which nothing is known.) We have then, as the grand total of the silver product from the discovery of America to the present time, $7,150,000,000.-Mines. The silver produced in Great Britain is extracted from an argentiferous lead, to the amount of 550,000 to 700,000 oz. annually (in 1872, 628,000 oz.). The celebrated Kongsberg mines in Norway, discovered in 1623, have been worked almost continually since. The ore occurs in parallel belts of rock, intercalated in gneiss and crystalline schists, and impregnated with sulphides of iron, copper, zinc, and sometimes lead, cobalt, and silver. Fissure veins traverse these belts occasionally, and are argentiferous at the intersection only. Beautiful specimens of native silver occur. The total product of the Kongsberg mines from 1624 to 1864 was 1,817,510 lbs. troy of silver, of which 1,332,485 lbs. was produced before 1805 and 463,498 lbs. after 1815, the intervening period being one of discouragement. The yield for the 30 years preceding 1865 averaged $350,000 annually. The silver mines of Sweden are at present insignificant, and the total product in 1871 was officially reported at but 975 kilos. The silver mines of the Austro-Hungarian monarchy are principally comprised in Hungary, Transylvania, and Bohemia. The A considerable portion of this increase is due Schemnitz district in Hungary (the seat of a to the importation of rich silver ores from paid dividends. The Himmelfahrt, which is now the leading mine, in 1873 yielded 11,912 metric tons of silver, copper, and lead ores, valued at about $430,000. In 1874 it produced about 7,100 tons of dressed ores, sold to the furnaces for about $328,000. The total yield of this mine to the end of 1874 had been 527,103 kilos of silver (worth about $23,000,000), besides lead, copper, zinc, sulphur, arsenic, and nickel. The chief other productive mines near Freiberg, with the value of their total product (including lead, &c.), as paid by the smelting works, for 1873, are as follows: Himmelsfürst, $202,500; Vereinigt Feld, $114,750; Churprinz, $74,000; Alte Hoffnung, $61,000; Gesegnete Bergmannshoffnung, $60,750; Alte Hoffnung Gottes, $52,750; Junge hohe Birke, $45,450; and Beschert Glück, $34,600. The principal silver mines of Prussia are in the Hartz, formerly belonging to Hanover. The product of Prussian smelting works in 1872 was 162,553 lbs. of silver, worth about $3,600,000; in 1873, 231,920 lbs., worth about $5,000,000. The total product of silver from the smelting works of all Germany was as follows in the years named: 1850 1870 YEARS. Centner. 101,448 124.103 185,847 Value in round numbers. $2,234,000 4,162,000 metal from its ores. At the time of the visit of Humboldt operations were carried on in from 4,000 to 5,000 localities, which might all be included in about 3,000 distinct mines. These were scattered along the range of the Cordilleras in eight groups, the principal of which, known as the central group, contained the famous mining districts of Guanajuato, Catorce, Zacatecas, and Sombrerete, and furnished more than half of all the silver produced in Mexico. The mines of Guanajuato, opened in 1558, are all upon the greât vein, known as the veta madre, in the range of por North and South America for metallurgical treatment, and another portion to the improved processes of extraction. The product from German ores is probably not more than $3,000,000. France is not a silver-ore producing country; but the separation of silver from argentiferous lead ores is carried on to a considerable extent. In 1865 it produced 31,997 kilos of silver, worth $1,414,000; in 1869 (the year before the war), 46,299 kilos, worth $2,020,000. No Spanish silver mines were specially important after the middle ages down to 1825, except those of Guadalcanal and Cazalla, N. E. of Seville, which were profit-phyritic hills the summits of which are from ably worked by the government in the 16th century, producing altogether 400,223 marks of silver; afterward they passed into private hands, and in the beginning of the 17th century are said to have produced 170 marks daily. They were finally abandoned, and allowed to fill with water. In 1825 mining was revived in Spain; in 1839 the famous silver mines of the Sierra Almagrera (N. and S. veins in slate, carrying argentiferous galena, with some silver chloride), in the province of Almeria, were discovered, and in 1843 those of Hiendelaencina (narrow E. and W. veins of silver sulphide and chloride, without lead), in the province of Guadalajara. The Herminia mine, in the Sierra Almagrera, in 1874 produced 18,940 quintals of ore, containing 342,325 lbs. of lead and 41,670 Spanish oz. (3,205 lbs. troy) of silver. The product of the mine in the early part of 1875 was at the rate of about 10,000 lbs. troy per annum. value of the work lead is about 20 oz. troy per ton avoirdupois. The product of the mines of Hiendelaencina from January, 1847, to July, 1866, was 7,578,536 oz. troy. They have declined in yield since 1858. By the application of the Pattinson process to the argentiferous galenas of the numerous lead mines of Spain, the production of silver has been increased. The export of lead in 1874 was 86,802,271 kilos, valued at 47,034,022 pesetas. This indicates a value of about $1,700,000 for the silver in the lead. The product of Russia in 1871, from 21 mines of argentiferous galena, was 1,740 tons of lead and 29,000 lbs. of silver. -The conquest of Mexico by Cortes in 1519-'21 was soon followed by the development of the wonderfully rich silver mines of that country. The metal was known to the ancient Aztecs, and was worked by them into numerous ornamental and useful articles; but among the treasures of Montezuma the quantity of silver was small compared with that of gold, and gave little promise of the unbounded resources of the argentiferous mines of his territories. During the 16th century these were opened and extensively worked by the Spaniards in Guanajuato, Zacatecas, and other neighboring districts; and in the 17th and 18th centuries their production was greatly increased by reason of the greater abundance of quicksilver and its more general employment in separating the The average 9,000 to 9,500 ft. above the sea, but only about The Mexico and South America, are now reported to be flooded in their depths. In the Cerro de Fernando at Hualgayoc, near Micuipamba, rich ores were discovered in 1771, and now, it is said, about 1,400 pits are opened in the hill. Other mining districts in Peru are Gualanca in the province of Huamalies, Pasco, Lucanas, and Huantajaya. Cerro de Pasco has been especially famous for its large production. A town is built upon the site of the mines, and the openings to many of them are through the houses of the miners. The production of Peru until within a few years was very small, probably not more than $2,500,000 annually, and it is a very difficult field for mining. Roads, mules, labor, and fuel are all wanting. The ores (except the pacos or ferruginous earths of Cerro de Pasco), being complex sulphurets, are exceedingly refractory. In the absence of better fuel, llama dung is employed for roasting at several establishments. But the country is full of undeveloped veins, and coal has been discovered in abundance, while railroads are rapidly extending into the interior. In Bolivia, besides the mines of Potosí, are those of Portugalete in the province of Chichas, celebrated for the richness of their ores, which produce six to eight times as much silver to the ton as those of Potosí. Other mines are worked in the same district. The mines of Lipes have been very productive, and those also of La Plata, Porco, Carangas, and Oruro. The earlier silver mines worked in Chili were in the province of Santiago and in the mineral district of Arqueros, about 17 leagues from Coquimbo. The production was not large, and almost ceased upon the opening of the rich mines near Copiapó in the province of Atacama. Within a circuit of 25 leagues from this city there are 19 silver-mining districts, of which those of Chañarcillo and Tres Puntas are the most important. The metal is found in a variety of combinations, as a sulphuret, chloride, chlorobromide, and iodide; it is also associated with arsenic, antimony, and mercury, and is sometimes abundant in a native state. The mines are in a country difficult of access, quite unproductive even in the timber and fuel required for mining, almost entirely destitute of water, and cold and dreary. A new and rich district has been developed at Caracoles, where the ores, like most of those of Co greatest proportion of silver in every mining | 000,000. The mines, like so many others in district of Mexico is obtained from the sulphuret of silver, an ore of gray color disseminated through the quartz matrix in minute particles, and more or less combined with other metals. The other varieties of argentiferous ores are numerous, but comparatively small in quantity; they are the chloride of silver, ruby silver, native silver, argentiferous pyrites, and argentiferous galena. The comparative quantities of these at the different mines are very variable. Until the present century the ores were extracted altogether by the rude methods of the native Indians. They brought them upon their backs up the long flights of thousands of roughly formed steps, in loads of 240 to 380 lbs. each, while exposed all the time to the great heat of the mine. In 1821 the Mexican government offered facilities for foreigners to become interested with the natives in the mines. English mining companies were formed, and operations were undertaken with powerful machinery; but the adventures were almost universally unsuccessful, the nature of the country being extremely unfavorable for the introduction of heavy machines, as well as for keeping them in operation and repair. From the opening of the Mexican mines in the 16th century their production of silver has exceeded that of all other countries. A great stimulus was given to it by the amalgamating process devised by Medina at that early period in Mexico, and it soon attained an annual rate of from $2,000,000 to $3,000,000. This continued to increase till in the 18th century it rose to $23,000,000, which was about the production for the first ten years of the present century. After 1850 it increased, till for some years it exceeded the yield of all past periods. The total product, from the first working of the mines by the Spaniards to their expulsion by the Mexicans in 1821, was $2,368,952,000. A very promising field for silver mining is found in the state of Sinaloa and along the western slope of the Sierra Madre of Durango and Chihuahua. The port of Mazatlan is the base of supplies. Sinaloa is well wooded and watered; the ores are largely true silver ores, which can be treated by the Freiberg or the modified Washoe process. Some of the mines in the interior are exporting rich silver ores to Europe; others are reported to be earning good profits with stamp mills. Central America has no silver mines that are worked to much ex-piapó, are chlorides, and easy to reduce.tent; but rich ores are known to exist in Honduras, Nicaragua, and Costa Rica.—The famous mines of Potosí in Peru (now in Bolivia) were discovered in 1545 by an Indian hunter, Diego Hualca, who, according to Acosta, accidentally exposed native lumps of the precious metal in the roots of a bush which he pulled from the ground. For 20 years succeeding 1557 the annual production of the mines of this region was about $2,200,000, and the total product up to the present time is rated at over $1,300, Silver mining in the western United States, apart from the early operations of the Spaniards in New Mexico and perhaps Arizona, dates from the discovery in 1859, on the E. flank of the Sierra Nevada, in the present state of Nevada, of the now famous Comstock lode. (See NEVADA.) No equally important argentiferous deposit has since been discovered; and, in view of the most recent exposures of vast bodies of ore at great depth on the Comstock, it may be doubted whether its |