THE COMSTOOK LODE. 13 



of modern eruptive rocks, belonging to the volcanic family, and ranging in 

 date, probably, from as early as the late Miocene up to the Glacial period. Folds 

 of more or less complexity, twisted and warped by longitudinal forces, often 

 compressed into a series of zigzags, sometimes masked by outbursts of granite, 

 syenitic granite or syenite, and, lastly, built upon by or frequently buried be- 

 neath immense accumulations of volcanic material : these are the characteristic 

 features of mountain chains. They are usually meridional and parallel, and 

 separated by valleys which are filled to a general level by Quarternary detritus, 

 the result of erosion from the early Cretaceous period down to the present time. 

 The east slope of the Sierras, directly facing the Washoe region, is, in brief, a 

 relic of metamorphic schists and slates, skirting the foot-hills and resting at 

 high east and west angles against the great granite body which, for many miles 

 to the southward, forms not only the summit but the main mass of the range. 

 Rising through the granite, and forming an eastern summit, is a lofty mass of 

 sanidin-trachyte, of a dull chocolate color, and only remarkable for the beau- 

 tifully regular prisms of black mica which intersect it. The ridge known 

 as the Washoe Mountains is of this trachyte; its culminating height, Washoe 

 Peak, lies directly west and across the valley from Mount Davidson, the center 

 and summit of the Virginia mining region. 



Little can be learned of the ancient structure of the Virginia Range, for 

 eight-tenths of its mass are made up of volcanic rocks. Only at rare intervals, 

 where deep erosion lays bare the original range, or where its hard summits 

 have been lifted above the volcanic flows, is there any clue to the materials or 

 position of the ancient chain. Mount Davidson is one of these relics, being 

 composed of syenite. Inclined against the base of this mass, and in the bot- 

 toms of ravines, eroded in the volcanic material, occur considerable hills ot 

 metamorphic rocks, schists, limestones, graphitic shales, and slates. South- 

 ward, in the canon of the Carson, and in the ravines of the Pine Nut hills, are 

 uplifted slates and carbonaceous shales associated mth irregular limestone beds, 

 the whole surrounded and limited by volcanic (andesitic) rocks. Still further 

 southward, the crest ridge of the Pine Nut region, which is a continuation of 

 the Virginia Range, is syenitic granite, forming high rugged crags, of an 

 extremely picturesque aspect. Every analogy would point to the belief that 

 these relics of aqueous rocks, and the granitic masses accompanying them, are 



