178 



University of California Publications. 



[Geology 



STATEMENT OF THE PROBLEM. 



In these days of rapid advance in our knowledge of the genesis 

 of ore bodies, it becomes necessary constantly to test old ideas by 

 new conceptions. Particularly does this apply to our recent ideas 

 on secondary enrichments of ore deposits. The mining world is 

 awaiting eagerly more exact knowledge on the part of geologists, 

 that the cost of locating valuable ore bodies and developing them 

 properly may be reduced. The structure of the Comstock lode, 

 and the genesis of its ores, have been treated by several investiga- 

 tors, but even yet, many of the vital questions connected therewith 

 are unsettled. The somewhat overdone tendency to make every 

 ore deposit correspond to a "type," and to regard much, if not 

 all, as already "having happened," has been productive of con- 

 siderable error. Fortunately, with our ever widening view, these 

 marks of immature science are disappearing. The Comstock is 

 yet largely an unsolved problem, withal we know much about it, 

 and the following notes contributed to its solution are the result 

 of numerous short trips to the lode while the writer was engaged 

 in other work.* The peculiar bonanzas of Virginia City have 

 never been satisfactorily accounted for, nor the form of the lode 

 as a whole. This paper is offered as a slight contribution to the 

 study of ore deposits, and on account of the immediate bearing of 

 its contents upon practical mining matters, it is issued at this 

 time. 



EAST-WEST FAULTS. 



There is a much greater development of east-west faulting 

 than has been noted by previous observers. These faults are of 

 the utmost importance, both in the structure of the lode and in 



* The author 's acknowledgments are due to Mr. James McKinty and 

 Mr. Thomas McCormiek, superintendent and foreman, respectively, of the 

 C. & C. mine, for their aid in obtaining deep mine waters; Mr. B. E. Everett 

 for aid in obtaining mine waters and rock specimens; Mr. M. W. Fox, and 

 Mr. Frank Higginson, general manager and superintendent, respectively, of 

 the Hale and Noreross; and particularly to Mr. G. McM. Boss, whose great 

 interest in these matters lies at the bottom of this short paper. Mr. Eoss 

 was until recently superintendent of the Ophir and Mexican mines. The 

 author wishes also to state his indebtedness to former publications upon the 

 Comstock, particularly Becker's Monograph and King's Survey of the 

 Fortieth Parallel. These works have been freely consulted on points not 

 now to be determined in the mines. 



Becker's Atlas should be consulted for maps, etc. 



