CHAPTER XI. 



DESCRIPTIVE GEOLOGY OF THE STEAMBOAT SPRINGS 



DISTRICT. 



[Atlas Slieet XIV.] 



Character of the district. — SteaiTiboat Spriiigs lic.s Ijetweeu the Sierra Nevada 

 and tlie Virginia Range, at the western edge of the Great Basin. The 

 forests and snows of the great Sierra are in sight a few miles away, but in 

 the neighborhood of the springs only sage brush grows without irrigation. 

 The soil in the lowlands, however, is fertile, and sufficient w^ater is avail- 

 able to bring a considerable surface under cultivation. The hills are for 

 the most part bare rock, as geologists love to see them. Many of the 

 exposures are whitened or reddened by solfataric action, and on cool days 

 tall columns of steam rise from the numerous hot springs, giving the local- 

 ity a weird appearance. Steamboat Springs is only six miles from the 

 Comstock lode and lies at the northwest base of Mt. Davidson, on the 

 eastern flank of which is the great .silver vein. The intervening space is for 

 the most part covered with lavas, one of the sheets of which seems to be 

 continuous for the entire distance. All the rocks which occur at Steam- 

 boat are also found in the immediate neighborhood of the Comstock, and 

 the fissures of the two localities are approximately parallel cracks, with 

 many points of resemblance. Steamboat affords fine opportunities for the 

 investigation of massive rocks, and the occurrences here serve to throw 

 much additional light on the rocks of the Washoe district, described by me 

 in Vol. Ill of this series. The proximity of the areas permitted me to 

 make direct comparisons during the present investigation. The spring 



