MINING. 301 



tain, it was necessary for them to cut tunnels through a rim of 

 rock ; but now that many of the tunnels have drained away all 

 the water, they are started up on the hill-side above the rock, and 

 cut in sloping downward, so that the hard bed-rock is avoided, 

 and in many places the tunnels made on this plan may run all 

 the way through soft dirt. It is established beyond all reason- 

 able doubt, that the auriferous deposit under the basalt was 

 once the bed of an ancient river. Every mark indicates it. 

 The wide water-worn bed, the bends, the bars, the deposits of 

 gravel in eddies, the collection of coarse gold in the centre, 

 the position of the large flat stones, all pointing down stream, 

 the remains of fresh-water mollusks, and the beds of little 

 tributary streams — all these are conclusive proof that a large 

 river once ran where this mountain now stands. The pay-dirt 

 is a tough clay filled with large stones, and is from a foot to 

 six feet deep. In one placpe a claim one hundred superficial 

 feet square yielded seventy-five thousand dollars. The dis- 

 tance from the outside of the mountain to the pay-dirt, varies 

 from six to twelve hundred feet. About ten miles east of 

 Sonora is the Soulsby quartz lead, one of the richest in the 

 state. 



§ 225. Mono and Mariposa. — Eastward of Tuolumne, east 

 of the summit of the Sierra Nevada, and within the limits of 

 the Great Basin, lies the county of Mono, which contains the 

 gold placers of Mono Lake and Walker Rivei', and the silver 

 lodes of Esmeralda. The placers of Walker and Mono are 

 neither extensive nor rich ; water is scarce ; and the winters 

 are so cold that mining is necessarily interrupted. The Walker 

 diggings are seventy-five miles southward from Carson City, 

 and the Mono placers are twenty-five miles further in the same 

 direction. The Esmeralda mines are in a nest of mountains of 

 the same name, most of the ridges of which run north and 

 south, and are composed of eruptive rocks, such as trap and 

 basalt, with occasional greenstone and porphyry. The argen- 

 tiferous region lies in a rugged part of the mountains, about 

 five thousand feet above the level of the sea. The ore is all a 



