DISTRIBUTION OF THE PALEOZOIC. 205 



if not far beyond. Throughout this entire distance, wherever they have 

 been studied, these limestones maintain a great thickness of strata. At the 

 southern end of this belt near Quartz Peak, the Silurian and Devonian 

 limestones are estimated at G,40() feet, and at Ravens Nest, just south of 

 the Humboldt River, the estimate gives 5,500 feet, while at Eureka they 

 present even a greater thickness. 



As yet we know but little about the occurrences and distribution of the 

 Diamond Peak quartzite. According to the section at Quartz Peak it is 

 wholly wanting. In the Diamond Range at Eureka, it attains a thickness 

 of 3,000 feet ; on the opposite side of the valley in the Pinon Range it can 

 not measure less, and at Ravens Nest it attains a development of 7,000 

 feet. In the northern part of Nevada we see an enormous development of 

 arenaceous beds separating a Devonian from a Carboniferous fayua. This 

 material thins out to the south, and in place of it we find a continuous 

 limestone body extending all the way from the Eureka quartzite well 

 up into the Carboniferous, without any well defined intervening sili- 

 ceous horizon. Too few observations have "been made to determine 

 the geological history or geographical distribution of the Upper 

 Silurian and Devonian rocks. As to the character of their sedi- 

 mentation eastward, the thickening or thinning out of strata, or their 

 lithological transitions, we know but little. It is a most significant fact, 

 and one by no means easy to explain, that the entire series of beds included 

 within the second period in which the Paleozoic rocks of Eureka have been 

 classed, based upon their physical history, should apparently be wanting 

 over such large areas in Utah and eastern Nevada. In other localities, while 

 they may not be wholly wanting, the}' appear to be represented by thin 

 beds of Lone Mountain strata, identified by a stray Halysites, and the Devo- 

 nian by an occasional Atri/pa. 



Another interesting fact as regards the position of these rocks is this : 

 Notwithstanding the enormous thickness of the Upper Silurian and Devo- 

 nian beds at Eureka, the same relative position which has been observed in 

 so maiiv plac.es elsewhere, with the Coal-measures resting upon the under- 

 lying Pogonip, may be seen here, the Upper Silurian and Devonian being 

 absent. The occurrence of the two limestone bodies lying in juxtaposition 

 may be seen all along the east base of Prospect Ridge, where the Iloosac 



