ILLUSTRATIONS. 
Page' 
Plate  I.  Geologic  map  of  Tonopah  mining  district,  Nevada 92 
Fig.    1.  Sketch  map  of  the  Fairbanks  district,  Alaska 65 
2.  Horizontal  plan  of  portion  of  Mizpah  vein,  Tonopah,  Nev 100 
3.  Map  showing  outcropping  veins  at  Tonopah,  Nev 101 
4.  Detailed  vertical  section  of  one  of  the  minor  Valley  View  veins  at 
surface,  Tonopah,  Nev 104 
5.  Ideal  cross  section  of  Tonopah  rocks 108 
6.  Map  of  the  York  tin  region,  Alaska „ 155 
7.  Sketch  map  of  the  Deer  Creek  coal  field,  Arizona 241 
8.  Map  of  the  Elders  Ridge  coal  field,  Pennsylvania 313 
9.  Map  of  the  Meadow  Branch  coal  field,  West  Virginia 331 
10.  Sketch  map  of  the  Boulder  oil  field,  Colorado 384 
11.  Sketch  map  of  eastern  half  of  Greene  County,  Pa 397 
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