GEOLOGY. 51 



is the Kern River district, including White River between 

 35° and 36° on the western slope of the Sierra Nevada. There 

 are gold diggings on the San Gabriel and Santa Anita Rivers, 

 and in the San Francisquito caiion in Los Angeles county. In 

 the Colorado valley, fifty miles above Fort Yuma, gold has 

 been found. IsTearly every one of the coast counties has more 

 or less gold : it has been found in the valleys of Russian River, 

 Putah Creek, Sequel Creek, Coyote Creek, the Salinas River, 

 and in the earth in wdiich the city of San Francisco is built. 



§ 37. Auriferous Lodes. — Gold is found fastened in stony 

 veins, and loose in earthy matter : the latter called placer dig- 

 gings, the former auriferous quartz lodes. 



It is the accepted theory among geologists that all gold was 

 once enclosed in quartz lodes, and that the gold in the placers 

 Avas obtained from the disintegration or breaking up of the 

 lodes. The surface of the earth w^as once all rock* the earthy 

 matter was formed by the action of air and w^ater on this 

 rock. The earthy matter was then deposited in diluvium, 

 among which was the gold that had existed in the rock pre- 

 vious to its disintegration. 



Gold is sometimes found in granite, syenite, limestone, slate, 

 and other rocks ; but the auriferous lodes, regularly worked, 

 are all of quartz. Most of the quartz veins run parallel with 

 the main divide of the Sierra — that is, north-northwest and 

 south-southeast — are from a line to thirty feet thick, and are 

 nearly perpendicular, dipping to the eastw^ard. They are be- 

 tween two thousand and six thousand feet above the sea. The 

 general color of the rock is white, occasionally bluish, fre- 

 quently reddish-brown, the color of iron-rust, derived from the 

 decomposition of iron pyrites. In some veins the rock is com- 

 pact, and then it is usually very white ; in others it is full of 

 cracks and crevices, and ready to break into small pieces with 

 a little pounding. Most of the veins have gold in them; only 

 a few have enough to pay for w^orking. The gold is in par- 

 ticles of irregular shape, but with some regularity of size, scat- 

 tered through tlie rock. The particles are seldom larger than 



