CHAPTER XVI. 



ADAMS HILX. 



Topography and formations.— The summit of Adams Hill is situated about 3,400 

 feet nearly due north from the top of Ruby Hill. The hill is a gentle ele- 

 vation which rises to a height of 6,940 feet above sea-level and slopes with 

 a gradual descent toward the valleys on the west and north. It is divided 

 from Ruby Hill by a moderately deep ravine which enters Spring Valley. 

 The principal part of the hill is composed of Hamburg limestone, the 

 Secret Canon shale forming a band running east and west along its south- 

 ern flank, and the Hamburg shale making its appearance in a like manner 

 on the northern slope. To the north of the Hamburg shale and to the east 

 of the Hamburg limestone the Pogonip limestone is exposed. The non- 

 appearance of the Hamburg shale between the Hamburg and Pogonip 

 limestones at the latter place is due to the continuation of the Jackson fault 

 described by Mr. Hague. North of the Hamburg shale, in the Pogonip 

 limestone, there is a large outcrop of quartz-porphyry, and still further on 

 in the same rock a smaller overflow which is visible underground in the 

 workings of the Bullwhacker mine. The dip of all the formations of 

 Adams Hill, including the Secret Canon shale, is apparently to the north. 



structure.— Although the mining explorations which have been made on 

 Adams Hill are not sufficient to give a complete idea of its internal struc- 

 ture, they are, nevertheless, extensive enough to show that it is composed 

 of a bed of limestone underlain and overlain by distinct beds of shale, all 

 of which have a variable dip to the north. There is much less evidence of 

 faulting and crushing in Adams Hill than there is in either Ruby Hill or 

 Prospect Mountain. The rock does not seem to have been subjected to the 

 enormous pressure that has caused the grinding up of the limestone in 



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