﻿322 
  

  

  PBOCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  [Apr. 
  13, 
  

  

  unconformable 
  to 
  them. 
  Mount 
  Davidson 
  and 
  a 
  part 
  of 
  the 
  second 
  

   range 
  or 
  summit 
  of 
  the 
  Sierra 
  are 
  sketched 
  in 
  the 
  background, 
  so 
  

   as 
  to 
  show 
  as 
  nearly 
  as 
  possible 
  their 
  position 
  relatively 
  to 
  the 
  

   section 
  on 
  the 
  plain. 
  The 
  porphyritic 
  conglomerate 
  probably 
  ex- 
  

   tends 
  through 
  the 
  Mount 
  Davidson 
  and 
  Washoe 
  Ranges, 
  but 
  it 
  was 
  

   not 
  seen 
  there. 
  The 
  second 
  outcrop 
  to 
  the 
  right 
  of 
  Carson 
  River 
  

   would 
  seem, 
  from 
  the 
  section, 
  to 
  sustain 
  the 
  relation 
  of 
  a 
  dyke 
  to 
  

   the 
  tilted 
  beds 
  containing 
  the 
  brown 
  coal, 
  but 
  it 
  is 
  merely 
  intended 
  

   to 
  indicate 
  their 
  nonconformity. 
  In 
  describing 
  the 
  granite 
  of 
  the 
  

   western 
  slope 
  of 
  the 
  Sierra 
  Nevada, 
  near 
  the 
  plains 
  of 
  the 
  Great 
  

   Basin, 
  it 
  should 
  have 
  been 
  observed, 
  in 
  addition 
  to 
  the 
  description 
  

   of 
  the 
  outcrops 
  of 
  metamorphic 
  rocks 
  near 
  Genoa, 
  that 
  in 
  the 
  pass 
  

   to 
  Lake 
  Bigler, 
  a 
  few 
  miles 
  south 
  of 
  Carson, 
  the 
  lower 
  exposures 
  

   and 
  ridges 
  of 
  the 
  granite 
  present 
  some 
  remarkable 
  evidences 
  of 
  

   former 
  stratification, 
  as 
  seen 
  in 
  the 
  accompanying 
  outline-sketch 
  

   (fig. 
  2). 
  These 
  vertical 
  masses 
  of 
  rock 
  rise 
  from 
  50 
  to 
  150 
  feet 
  

   above 
  the 
  crests 
  of 
  the 
  ridges. 
  This 
  structure 
  is 
  brought 
  out 
  more 
  

   clearly 
  by 
  weathering. 
  

  

  III. 
  Hot 
  Springs. 
  — 
  Thermal 
  springs 
  of 
  considerable 
  volume 
  are 
  

   numerous 
  in 
  various 
  parts 
  of 
  the 
  Territory 
  ; 
  but 
  the 
  most 
  extensive 
  

   and 
  interesting 
  are, 
  probably, 
  those 
  known 
  as 
  the 
  Steamboat 
  Springs, 
  

   about 
  ten 
  miles 
  north-west 
  of 
  Virginia 
  City, 
  and 
  bordering 
  on 
  

   "Washoe 
  Creek. 
  

  

  The 
  position 
  of 
  these 
  springs 
  is 
  marked 
  by 
  columns 
  of 
  steam 
  

   rising 
  in 
  a 
  line 
  above 
  a 
  white 
  mound, 
  about 
  a 
  quarter 
  of 
  a 
  mile 
  

   long 
  and 
  forty 
  or 
  fifty 
  feet 
  higher 
  than 
  the 
  bed 
  of 
  the 
  creek. 
  Two 
  

   or 
  three 
  fissures 
  extend 
  through 
  the 
  centre 
  of 
  the 
  whole 
  length 
  of 
  

   the 
  mound, 
  and 
  it 
  is 
  from 
  these, 
  at 
  different 
  points, 
  that 
  jets 
  of 
  

   steam 
  ascend. 
  The 
  section 
  (fig. 
  3) 
  will 
  show 
  the 
  form 
  of 
  the 
  mound 
  

   and 
  the 
  relation 
  of 
  the 
  springs 
  to 
  the 
  adjoining 
  rocks. 
  

  

  Fig. 
  3. 
  — 
  Section 
  across 
  the 
  Steamboat 
  Springs. 
  

  

  Washoe 
  Creek. 
  

  

  

  C. 
  Granite, 
  G. 
  Gravel. 
  L. 
  Limestone. 
  P. 
  Porphyry. 
  

   S. 
  Deposit 
  from 
  the 
  springs. 
  

  

  The 
  direction 
  of 
  the 
  fissures 
  is 
  15° 
  to 
  20° 
  N. 
  of 
  W., 
  apparently 
  

   following 
  the 
  line 
  of 
  division 
  between 
  compact 
  grey 
  granite, 
  like 
  

   that 
  of 
  the 
  Sierra 
  Nevada, 
  and 
  a 
  bed 
  of 
  porphyry 
  ; 
  though 
  this 
  could 
  

   not 
  be 
  ascertained 
  with 
  any 
  certainty, 
  owing 
  to 
  the 
  thick 
  deposit 
  

   produced 
  by 
  the 
  springs 
  and 
  the 
  alluvium 
  beyond. 
  They 
  vary 
  from 
  

   three 
  to 
  twelve 
  inches 
  in 
  width, 
  and 
  are 
  vertical 
  : 
  but 
  they 
  are 
  so 
  

   irregular 
  and 
  rugged 
  at 
  the 
  sides 
  that 
  they 
  cannot 
  be 
  probed 
  or 
  

  

  