284 GEOLOGY OP THE COMSTOCK LODE. 



250U-foot level for a considerable distance, and a horizontal section of 

 these workings is presented. It shows, in connection with the parallel 

 section 600 feet above, the growing tendency of the diabase contact to dip 

 towards the southeast and the great increase of crushed rock with increasing 

 depth. All preparations had been made to lay down the geology of the 

 Gold Hill mines at the corresponding level, when a flood rendered the 

 workings inaccessible. The map, however, at least indicates the continuity 

 of the vein in depth and parallelism of structure between this and the Sutro 

 Tunnel levels. 



Vertical projection of bonanzas. — The longitudinal Vertical projcctioH needs no 

 explanation, supplementing in an evident manner the other Atlas-sheets. 

 The disposition of the various bonanzas which it shows has been mentioned 

 in connection with the cross-sections of the Lode.^ 



Mine maps. — The cutire official mine maps are also presented, and will 

 enable those specially interested in the Lode to follow out many detiails of 

 structure. The notes on these maps as to walls, clay seams, etc., represent 

 the deliberate judgment of the surveyors and superintendents, and I have 

 found them, where accessible, for the most part, correct. They are left as 

 they stood on the originals, because the greater number of the localities 

 where they occur are inaccessible, and as a record of opinion of those 

 technically engaged in mining they have a distinct value, which would be 

 lost if partially replaced by my own determinations. Not all the galleries 

 appear on the maps, for, though the main workings have been carefully 

 plotted from the earliest times, unimportant drifts are often run without the 

 cooperation of the surveyor, and these sometimes escape record. The sur- 

 veyed galleries, shafts, and winzes aggregate about 155 miles, and the un- 

 recorded ones probably 30 miles additional.^ 



Claim-map. — The claim-map of the Washoe District forms a proper com- 

 plement to the mine maps. It shows the claims up to 1881 and distinguishes 



'In preparing all of the geological sections of the Lode, I was assisted by Mr. E. H. Stretch, 

 who is responsible only for the mapping, the geological determinations being my own. My determina- 

 tions, however, were greatly facilitated by Mr. Stretch'.s familiarity with the old workings, now for Ihj 

 most part inaccessible, and by his zealons .assistance in gathering data as to structure and lithology. 

 The longitudinal vertical projection of the Lode is entirely Mr. Stretch's work. 



'The official surveyors of the Comstock have been Messrs. I. E. James, R. H. Stretch, Marletto 

 & Hunt, T. D. Parkinson, Browne, Holi'mann & Craven, and L. F. J. Wrinkle. The contract for the 

 luaps was made with Messrs. Hoft'mann & Craven. 



