VI PREFACE. 



The claim iua|) was prepared by Messrs. Hoft'niann & Craven, sur- 

 veyors, on contract, and the mine maps were obtained through the same 

 firm from official sources. Some additions have been made to the claim 

 uiap by Mr. L. F. J. Wrinkle 



All the mine officers were most courteous and oflFered every facility for 

 the examination, often at great inconvenience to themselves. Mr. I. E. 

 James, superintendent of the Sierra Nevada, had prepared a considerable 

 number of slides, which, as well as his microscope, he placed at my disposal. 

 Mr. Forman, superintendent of the Forman Shaft; Captain Tayloi-, super- 

 intendent of the Yellow Jacket; and Mr. I. Requa, superintendent of the 

 Chollar, gave access to their collections, and to their temperature observa- 

 tions, as did also Mr. C. C. Thomas, superintendent of the Sutro Tunnel. 

 Mr. George J. Specht, surveyor, compiled the temperature observations of 

 the Tunnel and many other data, most of which will appear in another 

 volume. Mr. Forman also presented the Surve}' with a duplicate collection 

 of the rocks encountered in sinking his shaft, a specimen having been taken 

 ever)' five feet. Mr. W. H. Patton gave me extraordinary facilities in the 

 series of mines (from the Union to the Consolidated Virginia) under his super- 

 intendence; and Mr. Hugh Lamb, foreman of the Consolidated Virginia and 

 the California, spent much time in exploring with the party, and communi- 

 cated many acute and valuable observations gathered in his long experience 

 on the Lode. In short, from mine owners to coumion miners, an intelli- 

 gent interest in the objects of the Survey and a willingness to forward them 

 were manifested by all concerned. It is believed that the facts made out 

 with reference to the occurrence of ore will prove of sufficient practical 

 advantage to justify this interest. 



The lithological illustrations were all drawn and colored under mv con- 

 stant supervision. The endeavor was to reproduce the objects with absolute 

 fidelity, avoiding even the temptation to emphasize characteristic outlines or 

 tints, and the figures were not considered complete so long as an addition 

 or a change could be suggested. The work was put on the stones, of which 

 no fewer than eighteen w^ere requisite, by the same draughtsman who made 

 the drawings, ^Ir. G. K. Gardner, an<l the originals have thus not suffered 

 in liTliographic reproduction. It is safe to say that no lithographic illu.s- 



