METALS AND THEIR ORES. 47 



Ophir of Solomon's time. The Russian mines, that is, 

 those of the Urals and Siberia, were, till of late, the lar- 

 gest sources of gold, but the mines of California and Aus- 

 tralia far surpass them ; and it is stated by Professor 

 Dana that " the whole product of Europe, Asia, Africa, 

 and South America is far less at the present time than 

 is derived from Australia or the United States." 



92. Modes of Obtaining Gold. If the gold be in rock, 

 this is pounded up and sifted, and the sand thus obtained 

 washed in a pan. The gold being seven times heavier 

 than the same bulk of sand or gravel, those portions of 

 the sand which have gold attached to them subside to 

 the bottom of the pan, while the other portions, being 

 lighter, run off with the water. The portions which 

 subside are subjected to the amalgamation process, in 

 which mercury unites with the gold, forming an amal- 

 gam, and thus separates the metal from the sand. The 

 gold is then obtained from the amalgam by means which 

 are detailed in 213, Part II., where the whole process 

 is fully described. This sorting of gold by washing is 

 carried on extensively in nature in the alluvial washings, 

 as they are called. The grains and scales found in the 

 gravel and sand in the beds of streams and on their bor- 

 ders were once in rocks, which were worn away by 

 means that will be made clear to you in another part of 

 this book. The gold, on account of its weight, is always 

 lagging behind the materials that accompany it at the 

 start ; and the larger are the pieces of the metal, the less 

 distance are they carried, for small pieces have a larger 

 surface in proportion to their weight for the water to 

 act upon ( 193, Parti.). For the same reason, a round 

 piece is not carried as far as a scale. When there is a 

 rock in the path of a stream, the pieces of gold collect 

 there, the lighter gravel and sand being carried along 

 by the water. The formation of this "pocket" of gold 

 is very much like the gathering of the golden grains in 

 the bottom of the pan in artificial washing. Sometimes, 



