BULLETIN. 



]Nlo. G. 



(California Academy of Sciences. 



THE WASHOE ROCKS. 



BY GEO. F. BECKER. 

 INTRODUCTORY. 



It is well known to all who are interested in lithological 

 geology that Messrs. Hague and Iddings^ have denied the 

 validity of many of the results wdiich I reached concerning 

 the rocks of the Washoe district." These geologists frankly 

 confess that they commenced the study of the Washoe rocks 

 with a preconceived theory which the\' desired to prove, 

 and that they found my collections convenient for this pur- 

 pose.^ To prove their hypothesis, however, it was essential 

 to ignore or disprove a large part of m^^ conclusions as to 

 the structure of the district; for though my results were not 

 inconsistent with their main thesis, the region could not be 



Note i.— Bull. U. S. Geol. Survey. No. 17. 



Note '^. — Monograph III, U. S. Geol. Survey. 



Note ^ — They say, page 10: "In studying the collections of lavas from the 

 Pacific Coast volcanoes we were forcibly impressed with the insensible gra- 

 dations in the micro-structure in the groundmass of rocks of the same min- 

 eral composition from a purely glassy form to one wholly crystalline, and cor- 

 responding exactly in structure to a fine-grained granite-porphyry. * * - 

 In seeking a locality in the Great Basin which could afford the necessary 

 conditions for carrying out such an investigation as we desired to make, 

 showing the actual transition from the glassy to the granitic structure, it 

 was readily seen that the Washoe district was the only place offering suffi- 

 cient material for the work." 

 8— Bull. Gal. Acad. Sci. II. 6 Issued November 6, 1886 



