PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 479 



her boundaries are no important deposits of coal or iron. Hap- 

 pil}^ for us, within our own country we have all the various eco- 

 nomic minerals that are to be found upon the face of the wide 

 globe. I believe that there is no one which may not be found in 

 sufficient quantities to pay the expenses of mining. 



I will now point out the localities of the various mineral form- 

 ations of the United States, beginning with the later discoveries 

 upon the California coast and traveling eastward. 



First comes the gold formation of the Pacific. 



The deposits of auriferous sands, clays and gravels are distri- 

 buted from the liead of the Gulf of California, in a strip of country 

 varying from fifteen to seventy-five miles in width, across Cali- 

 fornia, Oregon, Washington, into the British possessions, and 

 probably as far north as the Sierra Nevada or Cr.scade mountains 

 extend. Upon the Sierra Nevada mountains the placer earth is 

 found at various altitudes. How came the gold in this placer 

 earth ? The theory is that at one time the whole of the Ameri- 

 can Continent, west of the Rocky mountains, was depressed four 

 or five thousand feet below the level of the sea. These plateaus 

 must have been formed while the continent was being elevated, 

 the water for a long time standing at a certain height. The 

 debris from the mountains would be washed down the slopes of 

 the valleys into these plateaus, in quantities proportioned to the 

 periods of time during which the earth was coming up from the 

 depth of the sea. Underneath the placer earth there is another 

 source of gold, for it is found in the rocks, the granite, the slate, 

 the serpentine and other rocks. The gold in these r;)cks is usu- 

 ally dist'ributed through three different systems of veins, varying 

 from a few inches to several feet in thickness. The gold is not 

 always uniformly diffused through the entire vein, but there is a 

 certain association of minerals that is never wanting. Almost 

 all minerals are related to each other in a certain way, certain 

 minerals being generally found together. The original form of 

 gold is sulphide of gold, and associated with it we always find 

 more or less sulphide of iron. All metals are universally distri- 

 buted, but in certain places they are gathered together in richer 

 profusion, and it is to these that I refer. Iron, lead, silver, 

 molybdenum, tellurium, osmium, manganese and copper are usu- 

 ally found associated. 



Coming down to the Santa Clara mountains, we find the richest 

 mines of quicksilver on the globe. In that neighborhood tin is 



