CHAPTER Xn. 



DESCRIPTIVE GEOLOGY OF THE OATHILL, GREAT 

 WESTERN, AND GREAT EASTERN DISTRICTS. 



Ill addition to the five districts described in the previous cliapters, 

 small areas surrounding the Napa Consolidated, Great Western, and Great 

 Eastern mines were mapped. The topography of these maps was executed 

 rapidly and without any effort to attain the degree of accuracy demanded 

 in the larger maps. It is nevertheless ver>- fairly done, and, excepting in 

 some minute details, the localities are excellently represented. I intrusted 

 the study of the geology of these districts to Mr. Turner. On going over 

 the surface area and the mines with him, at the completion of his examina- 

 tions, I could not see that anything liad been omitted or misrepresented. 

 This chapter is mainly prepared from his reports. 



The neighborhood of oathiii, — The rcgion iucludlng Oathill, the ^tna mines, 

 and the hot springs of Lidell, an area of, say, four miles by three, is one of 

 the most interesting in the entire quicksilver belt, and, had its character 

 been sufficiently undei'stood at an earlier period, an atlas sheet would have 

 been devoted to it. The deposits are numerous and differ very greatly 

 from one another in external form and in the character of the inclosing 

 rocks; some of them are also manifestly connected in the closest manner 

 with volcanic phenomena. These circumstances lend the deposits special 

 significance. The ^litna mines will be described in the next chapter, where 

 also a sketch map showing the relative positions of the deposits will be 

 found; but a few notes on these occurrences are needful to a proper appre- 



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