640 POPULAR SCIENCE MONTHLY. 



A similar deposit of silver was found in New Mexico about twenty 

 years ago and was christened the " Silver Lake " Mine. This was 

 worked profitably until the great fall in price of silver made the 

 operation a losing one. The " blanket " still contains millions of 

 ounces of silver, and it is probable that cheaper methods of recovering 

 the metal from the ore will be devised whenever the price of silver 

 shall have fallen low enough to enable it to take its place among the 

 so-called " economic " metals, having far wider application in the arts 

 than have the precious metals. At present silver holds an unfor- 

 tunate place " betwixt and between " the precious and the economic 

 metals. 



Twenty years ago aluminum was more valuable than silver is to- 

 day, and its production was correspondingly limited. Last year the 

 price was reduced to a point which so widely extended its use that 

 the production increased from 1,900 pounds in 1888 to more than 

 5,000,000 in 1898. 



Although the gold deposit in the Camp Floyd district in Utah al- 

 ready alluded to may actually contain several billions of dollars' worth 

 of gold, it will cost some billions of dollars' worth of labor and capital 

 to recover the precious metal and will consume much time in the 

 process; so that there is little reason to fear that gold will become so 

 plentiful on account of this discovery that it will cease to be regarded 

 as a precious metal. About forty years ago the assayers of the United 

 States Mint announced that the clay underlying the city of Phila- 

 delphia contained more gold than had been brought from California 

 and Australia, and this remarkable statement has never been disproved 

 or even questioned. The gold, however, still remains locked fast in 

 the clay, and the value of the precious metal has not yet fallen in con- 

 sequence of the announcement of this old discovery. At that time the 

 idea of profitably recovering gold from low-grade ores had not been 

 born, and it is an interesting fact to note that in California gold is now 

 being obtained from clay (by hydraulic washing methods) in which 

 there is but little more than the average proportion of gold to the ton 

 that the assayers found in the clay under the streets of Philadelphia. 

 This does not prove, however, that it will now pay to excavate un- 

 der the streets of the Quaker City, and undermine the buildings in 

 order to wash out this gold, and until Philadelphia shall be provided 

 with a far more copious water supply the most sanguine or suave pro- 

 moter of great undertakings would find it impossible to obtain sub- 

 scriptions to any scheme to recover this fugitive gold, or even, perhaps, 

 difficult to give away shares of stock to influential individuals either 

 in or out of councils. 



An impression has prevailed that the production of gold in South 

 Africa attained its maximum point in 1897, and that thenceforth the 



