CHAPTER II. 



THE OOMSTOOK LODE. 



Section I. — Geology op the washoe mining district — Virginia range — 

 General geology — Granite and beetajviorphics — Syenite — Propylite — 

 Andesite — Trachyte — Basalt. 



Section II. — Structure of the comstock lode in detail — Gold hill group — 

 Virginia group — Ophir group. 



Section III. — General structure and mode op occurrence of the comstock 

 LODE — Fissures — Horses — Clays — Quartz — Minerals — Bonanzas — Tem- 

 peratures — CHEIVnSTRY — PARAGENESIS — CONTINUANCE IN DEPTH — ^EilSUME. 



SECTION I. 



GEOLOGY OF THE WASHOE MINING DISTEICT. 



Virginia Range. — Among the most continuous and well defined of 

 those chains which diverge from the northwest trend of the Sierra Nevada to 

 a nearly meridional course is the Virginia Range. 



Leaving the Sierra where its eastern slope descends boldly to the plains 

 of the Great Basin, in latitude 38° 8', it stretches due north for a hundred 

 and fifty miles, terminating in terraced hills which sink under the quarternary 

 desert-beds of Mud Lake Valley. Its average breadth is about eighteen miles, 

 though no accurate mean width can be arrived at because of very unusual 

 variety of form. Three considerable rivers, from the snow drainage of the 

 Sierra, cut transversely through it, making canon passes which sink three or 

 four thousand feet below the general summit line. These are the Walker, 

 Carson and Truckee. Groups of comparatively low hills spread out from 

 either flank, those on the west not unfrequently connecting with the Sierra. 



The drainage which flows down its west side is gathered in a series of 

 ponds and small streams, finding its way at last into one of the three rivers, 

 and finally flowing through their canons to the sinking lakes on the east side. 



