2 78 THE POPULAR SCIENCE MONTHLY 



of Australia and California, who were gathering their golden harvest 

 with its aid, and in the two succeeding decades the silver miner also 

 impressed it extensively into his service. But as the various great 

 precious-metal mining districts of the world became connected with 

 fuel and labor centers by rail, the smelting industry arose and gradu- 

 ally supplanted most of the amalgamation process in which quick- 

 silver was the prime factor, and so the demand for it slowly declined. 

 The largest recorded yield occurred in the year 1877, when the output 

 amounted to 5,308 tons. In 1906 the world's jDroduction was only 

 3,964 tons. For many years now the silver miner has given up its 

 use almost altogether, but the Alaskan placer miner must still have it, 

 and there is yet a considerable consumption in those gold districts of 

 Africa and Australia, where smelters do not exist, and even in our own 

 west, at isolated or very low grade mines. At present the principal 

 demand is for the manufacture of mirrors, and certain scientific in- 

 struments like thermometers and barometers. There is good reason 

 to believe that there yet remains, undiscovered, in Asia, Africa and 

 South America, one or more great gold placer regions. When these 

 come to light the market for mercury will revive, and remain active 

 until the new fields are exhausted. There is no lack of its ores in 

 the crust of the earth. The metal has been produced in Spain for at 

 least three millenniums; the California deposits are far from being 

 exhausted, though they have been worked more energetically in the 

 last fifty or sixty years than the Spanish deposits since their dis- 

 covery, and the great mines of Huancavelica in Peru have hardly 

 been touched. So when the demand again arises, mother earth is 

 prepared to meet the drafts of her children, as usual. 



Nickel 



Fifty years ago this metal was practically unknown, except to the 

 scientist. Its successful production as an article of commerce began 

 in the United States about 1863, when it was detected in some copper 

 ore coming from the Lancaster Gap Mine in Pennsylvania. For the 

 next ten years, practically the entire world's output came from this 

 mine. At its best, however, the yield never exceeded 100 tons per 

 year, the metal commanding a price of $2.50 to $3 per pound, which 

 of course severely restricted its use. In 1867 one of its ores was 

 found in comparative abundance in the island of New Caledonia, a 

 French possession, lying to the northeast of Australia, and commercial 

 production from there began about 1874. In 1880 the metal was 

 discovered in copper ores coming from Sudbury district, Canada, on 

 the north shore of Lake Huron, and by 1886, a production began 

 which has since steadily increased until at the present time two thirds 

 of the annual world's crop of the metal comes from the later locality. 



