CHAPTER II. 



PREVIOUS INVESTIGATIONS OF THE COMSTOCK LODE. 



V. Richthofens report. — 111 1 865, Baroii Ferdinand von Richthofen made an 

 examination of the Comstock for the Suiro Tunnel Company, a report of 

 which was issued by that corporation, but never pubhshed in the proper sense 

 of the word.^ It met the ordinary fate of mine reports, and is now scarcely 

 obtainable. It was, however, a very important contribution to American 

 geology, and no one who has studied the Lode has failed to acknowledge his 

 indebtedness to it. The mines are now about six times as deep as at the 

 date of von Richthofen's examination, but his opinions and predictions have 

 for the most part been verified in a very remarkable manner; and had his 

 lithological determinations been as accurate as his insight into structure was 

 keen, I should have had little to do beyond confirming and amplifying upon 

 his views, in spite of immensely increased facilities for observation. In litho- 

 logy, as is well known, there has been almost a revolution since von Richt- 

 hofen wrote, and nothing is less strange than that some of his determina- 

 tions should fail to stand microscopic tests. On account of the rarity of 

 Baron von Richthofen's report, I take the liberty of reproducing almost 

 entire and verbatim its geological portions. In these days of diffuse writing 

 its conciseness must be regarded as one of its imjwrtant merits. 



Rocks of the district. — Tlie moi'C important rocks of the Washoe district are 

 as follows : 



Syenite, containing both orthoclase and oligoclase,- mica and epidote, 



' The Comstock Lode : its character and probable mode of continuauce iu depth. By Ferdinand 

 Barou RichtbofeD, Dr. Phil. (Nov. 22d, 18G5), San Francisco: published by the Sutro Tunnel Company. 

 Towne & Bacon, ])rinters, 1866. 83 pp. 8vo. 



-Professor Zirkel showed ten years later, by the help of the microscope, that this rock contains 

 exclusively plagioclase, and is therefore a diorite. 

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