Silver ores are found chiefly in veins which traverse the primary and the older of the secondary stratified rocks, but especially the former ; and also the unstratified rocks, such as granite and porphyry, which are associated with the above. In some of the mines in Peru, and in those of Kongsberg in Norway and Freiburg in Saxony, silver has been dis covered in masses weighing from 100 to 800 lbs. In the mines of Europe the veins are numerous and slender. In some of the mines in the Harz Mountains and in the Hungarian mines the veins occur in a small number of spots, and are of considerable dimensions. In three of the richest districts of Mexico there is only one principal vein, which is worked in different places. One of these veins, in the district of Guanaxuato, is from 130 to 148 feet wide, and it has been traced and worked to an extent of nearly eight miles.
In Mexico there were 500 mining establish ments, called Reales, at the time of Hum boldt's visit, and from 3000 to 4000 veins or masses were worked. The average richness of all the ores in Mexico is from 3 to 4 ounces per quintal of 102 lbs. In one of the Mexican mines a working of one hundred feet in length yielded in six months 432,274 lbs. troy of silver, equal in value to about 1,000,0001. In Chili some of the mines yield only 8 ounces in 5000 lbs. of ore ; but in the rich mine of Copiapo, discovered in 1832, the ore frequently contains 60 or 70 per cent. of silver. The average produce of the mines of Saxony is from 3 to 4 ounces in the quintal. The lead mines of Craven in Yorkshire con tained 230 ounces per ton ; and those of Cardiganshire, worked in the reign of Charles I., yielded 80 ounces. The average propor tion of the lead mines of the north of Eng• land is 12 ounces per ton, Even when the proportion of silver is so low as 8 ounces, or one grain per 8 lb., it has been found profit able to separate it. The produce of the Mexican mines averaged annually 4,800,0001. from 1793 to 1803, of which nineteen twentieths were silver. In the first ten years of the present century the average annual value was about 5,000,0001., the quantity of pure silver annually produced in that time being 1,410,650 troy lbs. The mines of Potosi in Peru are the most famous in South Ame rica. [PoTon.] The produce of the Chilian mines in 1832 was about 1,000,000 ounces. At the commencement of the present century Humboldt estimated the annual produce of the silver-mines of Chili, Peru, Buenos Ayres, and New Grenada, at nearly 700,000 lbs. troy, valued at 2,074,4761. sterling. The proportion of silver to gold produced from all the American mines was, early in the present century, as 62 to 1 ; and from the mines of countries as 52 to 1.
The most productive mines in Europe are those in Saxony, Austria, Hungary, Norway, Russia and Spain; but nearly all of these are less productive than they have been in former ages. The quantity found in Great Britain is
extremely small. Silver has ceased to be abundant in Asia, except perhaps in China. In Africa none is met with.
The silver mines of Copiapo are those which are now attracting the most attention. In 1824 they produced only 310 lbs. of silver ; about 1830 the yearly produce was 3000 lbs.; after the discovery of new veins in 1832 the production rose to 16,000 lbs.; and during the last eight years the following results have been exhibited:— 1813 39,599 lbs.
1814 61,497 „ 1845 76,723 „ 1846 80,397 „ 1847 102,052 ,.
1848 130,552 „ 1849 171,119 „ 1850 (about) 200,000 „ The proportional value of gold to silver was 12 and 10 to 1 from the Anglo-Saxon times to the discovery of America ; it is at present 14.28 to 1. In ancient Greece the proportion varied from 15 and 10 to 1, and in Rome from 12 and 7 to 1. Herodotus estimates it at 13 to 1. Since the discovery of America the proportion throughout the world has been between 17 and 14 to 1. The English silver coinage from 1600 to 1800 amounted to about 26,000,0001. ; from 1800 to 1840 about 11,000,0001.
There are nine mints in Mexico, at which the coinage was as follows in the years named.
Dollars.
1842 984,427 196,885 1843 620,532 124,106 1844 726,762 145,352 1845 783,910 156,782 1846 915,752 183,150 When silver is issued for coin, it is always alloyed with copper : the maximum of hard ness is produced by one-fifth of copper. One lb. of standard silver of the English coinage contains 11 oz. 2 dwts. of silver and 18 dwts. alloy, or 925 parts of pure silver in 1000 parts of standard silver. For purposes con nected with the manufacture of various articles of use and ornament, the alloy is greater. At Birmingham rolled sheets are made which do not contain more than 3 or 4 dwts. of silver to each lb. of the inferior metal.
Mr. Jacob estimates the annual consump tion of silver in the United Kingdom at 3,282,046 oz., valued at 820,5111. He distri• butes it as follows : That paying duty 1,375,316 oz.
That used in watch-cases 506,730 That used in plating 900,000 That for other minor purposes 500,000 3,282,046 The value of the stock of silver in the hands of the manufacturers and dealers is estimated by the same authority at 3,280,0001. The value of ornaments and utensils of the precious metals in Europe and America, if brought to the crucible, Mr. Jacob values at 400,000,0001., one fourth more than the value of the coined metals ; but Mr. BT`Culloch thinks these estimates too high ; and as they were made before the recent discovery of gold at California, some of them are likely to be modified by the abundance of gold.