GEOLOGY OF ADAMS HILL. 117 



made out except on the slopes of Ruby Hill, where the beds are distinctly 

 seen to pass beneath the limestone which caps the hill. Owing to this 

 abrupt curve, and the consequent breaking up of the strata, erosion has 

 cut a deep ravine in the quai-tzite. It is this ravine which separates Ruby 

 Hill from the main ridge. Overlying the quaitzite comes the Prospect Moun- 

 tain limestone forming the summit, the isolation of the hill being made com- 

 plete by the erosion of a broad, shallow ravine in the Secret Canyon shale 

 on the north side. 



Adams Hill, a flat topped mass of Hambm-g limestone, lies between 

 two nearly parallel ravines, one of which is eroded in the Secret Canyon or 

 underlying shale, and the other in the overlying Hamburg shale. On the 

 south side the Secret Canyon shale passes beneath the limestone, the Hue 

 of contact being well determined at the base of the hill, the dij) and strike 

 of the beds agreeing closely with those found on Ruby Hill. On the north 

 side of Adams Hill the Hamburg shales appear and are sharply defined by 

 the Umits of the Wide West ra\-iue. Beyond this latter ra\-iue the Pogonip 

 limestone comes in, gradually falling away beneath the deposits of Diamond 

 Valley. On PI. ii. Sec. 3, will be found a geological section drawn across 

 the strata from the Prospect Mountain quartzite on the soutli slope of Ruby 

 Hill to the Silurian limestone, the two Cambrian limestones forming the 

 summits of the two hills, the underlying one capping Ruby Hill and the 

 overlying one forming the mass of Adams Hill. The section is drawn 

 across a body of quailz-poi-php-y which breaks through the Pogonip lime- 

 stone. It is quite unlike any other crystalline body known in the district, 

 but it is of no special value as it has exerted little influence upon the 

 limestone, the latter being very little distui'bed and showing but few signs 

 of alteration. The age of the quartz-porphyry is unknown, as it ])enetrates 

 Silurian rocks only, but it is probably older than the rhyolites, which it in 

 no way resembles except in mineral composition. 



A comparison of the section refeiTcd to with the one across Prospect 

 Ridge (atlas sheet xiii) brings out the complete coiTelation between the two 

 series of beds, and the great similarity in the configuration of the two areas, 

 Ruby Hill and Adams Ilill to the north con-esponding with Prospect Ridge 

 and Hamburg- Ridjje of the east and west section of the main mountain. 



