PREFACE, 



The field work upon which the following report is based was begun in 

 July, 1881, and concluded late in 1882, the assays and many of the chem- 

 ical examinations being made during the progress of the field work, as occa- 

 sion required, in a temporary laboratory arranged for the purpose. 



In 1879 Mr. George F. Becker made a preliminary examination of the 

 more important mines. My report was prepared under his supervision, and 

 I am indebted to him for much valuable advice and assistance. In 1 880 

 Mr. Arnold Hague made a detailed survey of the general geology of the 

 district, an abstract of the results of which appeared in the Third Annual 

 Report of the Director. Upon this abstract I have relied for the determi- 

 nation of the stratigraphy and the relations of the district at large to the 

 ore-bearing formations. I also had the advantage of spending some days 

 in observations on the surface geology with Mr. Hague in 1881. The sur- 

 face geological map published with this report is taken from Mr. Hague's 

 atlas, which will be published with his memoir. 



Mr. C. R. Brown was my assistant during a great portion of the time 

 occupied by the field work and rendered important services in collecting 

 specimens and in the laboratory. Mr. N. Wescoatt, formerly surveyor for the 

 Richmond company, gave me much information in regard to the workings 

 of the Richmond mine, furnishing maps upon which the drawings of that 

 mine are based, as well as drawing Plate III. To Mr. E. Probert, manager, 

 and Mr. R. Eickard. superintendent, of this company, I am also indebted for 

 manv facilities, as well as to Messrs. Bryan, Longley, Morrison, and Davis, 

 employes Mr. T. J. Read, superintendent of the Eureka Consolidated, not 

 onlv furnished me important maps and information, but gave me every 



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