NOTES ON THE GREAT MOTHER LODE OP CALIFORNIA. 

 By J. H. COLLINS, F.6.S. 



A recent visit to the Pacific Coast on mining business, 

 afforded me the long wished for opportunity of visiting some of 

 the gold and silver regions of California and Nevada. The time at 

 my disposal was short, but I managed to see the lode, and being 

 already somewhat familiar with the gold districts of California 

 from a study of Prof. Whitney's work on the Auriferous Gravels, 

 I was enabled to profit by the short time at my disposal more 

 than would otherwise have been possible. I was particularly 

 interested in the gold belt, and its accompanying " Mother Lode," 

 from which these world-famous auriferous gravels have been 

 derived. The following is an outline of the characteristics of 

 this gold belt, which is closely subordinated to the Sierra Nevada, 

 and which perhaps owes its existence to the elevation of that 

 great chain. 



The great mountain range known as the Sierra Nevada of 

 California, is bounded on its eastern flank by an elevated plateau 

 of Jurassic rocks rich in silver, and on the western by less 

 elevated subordinate ranges of mica-slate, of highly altered 

 volcanic rocks, steeply inclined, and much metamorphosed 

 Triassic and Jurassic rocks, with few fossils, but rich in gold, and 

 by foot hills of nearly horizontal stratified tertiary sandstones. 



The main axis of the Sierra is granitic, rising in many 

 places to heights of 14,000 feet; and the period of its elevation 

 is clearly indicated by the particulars given above, as in the late 

 secondary or early tertiary times. 



The metamorphosed Jurassic rocks referred to, consist 

 largely, although not exclusively, of slates and shales. In many 

 places the strata stand about vertical, still more often they dip 

 steeply toward the central axis. Frequently they are but little 

 covered with detritus, and the peculiar weathered outcrops of the 

 slaty rocks, turned up on edge and projecting a few feet above 



