GEOLOGY. 341 



In the Dead Blue River most of the gravel, about 100 feet 

 above the bed-rock, is in pieces as large as a goose egg, 

 whereas in the Dead Brandy River, as I call it, running through 

 Laporte, Brandy City, Camptonville, and North San Juan, the 

 gravel is generally the size of a pigeon's egg. 



267. Fineness of Gold. Gold is found in many parts of 

 the State, but the principal mines are on the western slope of 

 the Sierra Nevada. Miners look for it wherever they find 

 granite, slate, and quartz together. It is mixed mechanically, 

 not chemically, with the rock and base metals that accompany 

 it ; but is not pure, for it is alloyed naturally with silver, and 

 sometimes with small proportions of copper, lead, and iron. 

 Usually about 12 per cent, of the weight of gold dust as sold 

 by the miners is silver, base metal, or adherent dirt ; leaving 

 88 per cent, as the pure gold. The variations are great, how- 

 ever, and persons who buy gold dust as a business, study the 

 ratio of impurity in the metal produced by the different mines. 

 This ratio is expressed in thousandths. Thus, we say that 

 perfectly fine gold is 1,000 fine ; American coin of standard 

 fineness is 900 fine, containing in 1,000 parts 100 of copper 

 to harden it ; the gold of Downieville ranges from 895 to 925 ; 

 that of North San Juan from 960 to 965 ; that of Grass 

 Valley from 800 to 840 ; that of Volcano, 870 ; Murphy's, 

 885 ; Mariposa, 700 to 820 ; and Kern River, 630. There are 

 often great variations in value between the gold found in two 

 claims separated by a distance of not more than half a mile. 



Placer gold is classified according to the size and form of 

 the placer in which it is found. Some pieces are small, oth- 

 ers large, smooth, or rough, in flat scales, round lumps, and 

 shaped like wires, cucumber seed, beans, pumpkin seeds, or 

 moccasins. I have washed out gold, nearly every piece of 

 which bore a remarkable resemblance to cucumber seed in form 

 and size. These peculiarities, however, are much less important 

 now than they were formerly, when the placer mines were in 

 the bloom of their production. Large nuggets of gold are 



