462 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



period, the first part of the mammalian era, carnivorous animals 

 seem to have been introduced, such as the panther, leopard, lion, 

 wolf, and dog. It would seem as if this was done as a necessary 

 part of the great idea of animal creation, to prevent the too 

 great increase of animal existence. 



It is a remarkable geological fact that during the whole of 

 this period, there is no proof that a single new mineral, or new 

 form of ore, of any particular value to the American people, 

 was deposited in the formations. California, Oregon, and the 

 whole country north and west of the Sierra Nevada, with the 

 gold and silver they abound in, were brought up after the rocks 

 of this period were formed. There seem to have been three 

 great successive stages in this process of placer-forming eleva- 

 tion. The first is now high up on the mountains; the last, from 

 which the gold has been washed into the auriferous sands, on the 

 level of the great plains. The gold is found only in the placer 

 earth, and where it has been washed out of the placer earth* 

 In no single instance has the placer earth failed to pay the men 

 who will work steadily at it through the week. This placer 

 earth extends from the southern part of California northwards, 

 to the extreme limit of the Russian possessions. From the best 

 information I can obtain, there is gold enough west of the Rocky 

 mountains to employ as many miners as wish to go there for 

 thousands of years. They must dig over the one hundred and 

 fiftieth part of the entire surface, west of the Rocky mountains, 

 to exhaust it. 



There is a system of gold veins running due north and south, 

 which is as old as the primitive era, and which always yields the 

 purest gold. The next system is of the age of the Rocky mountains 

 and lies in the same direction with the mountains. The gold is a 

 little softer, and begins to be contaminated with iron, lead, silver, 

 osmium, and iridium. The third system, lying east and west, is of 

 the tertiary age, and is always contaminated with other metals. 

 It is from these veins that the gold was washed out by the action 

 of the sea waves and carried into tlie placers, and thence into 

 the valleys of the Sacramento and other rivers. 



EXPLOSIVE PROJECTILES. 



Mr, Stetson, — I will divide this subject into three questions : 

 first, the proper form for explosive projectiles ; secondly, their 

 contents, and thirdly, the means for timing their explosion. The 



