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EUBY GEO UP. 489 



Eange. Its analysis was made by Prof. Thomas M. Drown, with the fol- 

 lowing result: 



Silica 70.46 



Alumina 15.36 



Ferrous oxide 2.93 



Manganous oxide 0.1 3 



Lime 2.79 



Magnesia 0.46 



Soda 3.89 



Potassa ■ 3.98 



Ignition 0.45 



100.45 

 The quartzite body doubtless represents a development of the Cam- 

 brian formation at this place. The direct contact of the overlying lime- 

 stones with these quartzites was not observed, but the general structure of 

 the intermediate portion of the range between this point and Egan Caiion 

 shows a series of limestones dipping to the west, having a strike somewhat 

 to the east and north, which would give room for the entire series of Silurian 

 and Devonian limestones between this point and Gosi-Ute Cailon. 



Ruby Geoup. — The broad low ridges constituting the Ruby Group, 

 to the west of the Egan Range, are made up of beds of light-gray and drab 

 limestones, whose structure is that of a broad synclinal, the angle of dip of 

 the beds being rarely more than 10°. On the low ridge which forms the 

 southern extension of Hamilton Butte, where crossed by the Overland Stage 

 Road, the limestones are mostly concealed beneath surface accumulations 

 and flows of basalt, which occupy the higher portions of the range, and 

 once probably extended across the valley to the west to the foot-hills of the 

 Ruby Group. Near the summit of the pass is a curious group of bare 

 knolls formed of rhyolitic tufa, whose soft, gray, porous mass has been worn 

 into cm-ious shapes. Their surface is covered by little indentations or cavi- 

 ties, left by the fragments of included lava which have fallen out, giving 

 them the appearance of a gigantic thimble or old-fashioned bee-hive ; hence 

 their name, "Tlie Beehives ". The mass of this tufa is of a light-gray color, 



