INDEX. 



Page. 

 Acid rocks. (See Rhyolite.) 



Ages of eruptions 39,50,59,01 



Alluvial cones 39,214,249,277 



Alluvial conglomerates, general discussion of 214 



Alumina in volcanic rocks 89,117,123 



Andesite, augitic: 



Classification of 101,103,109 



Occurring in the — 



Aquarius Plateau 293,295 



Awapa Plateau 275 



Fish Lake Plateau. 261.200 



Mount Hilgard 272 



Markagunt Plateau , 190,204 



Monroe Amphitheater 229,239 



Sevier Plateau 229,232,235,242 



Tushar 177,181 



Order of sequence 63,65,67,131-137 



Andesite, hornblendic: 



Classification of 110 



Occurrences 230,237,242,200 



Order of sequence 67,131-137 



Andesite, quartz. (See Dacite.) 



Aquarius Plateau, general discussion of (Chap. XII) 284 



Relations to District of the High Plateaus 5 



Argilloid trachyte. (See Trachyte. ) 



Archaean rocks . 143 



Awapa Plateau, general discussion of 272 



Relations to District of the High Plateaus. . 4 



Baldy, Mount 172 



Basalt: 



Chemical constitution of 123 



Classification of 101, 110 



Leucite Ill 



Liquidity of 135 



Nephelin Ill 



Order of sequence 67, 131-137 



Superfusion of 135 



Synthetic character of 122 



299 



