﻿ENDLicii.] 
  SAWATCH 
  RANGE- 
  — 
  PRESUME. 
  173 
  

  

  ore, 
  which 
  can 
  be 
  very 
  well 
  accomplished 
  with 
  ore 
  of 
  that 
  nature, 
  and 
  

   subsequently 
  smelting, 
  will 
  come 
  into 
  requisition. 
  

  

  EesumS 
  of 
  Chapter 
  III. 
  — 
  ^Viewing 
  the 
  portion 
  of 
  the 
  Sawatch 
  Range 
  

   treated 
  of 
  in 
  the 
  above 
  chapter 
  as 
  a 
  whole, 
  we 
  find 
  an 
  exceedingly 
  sim- 
  

   ple 
  chain 
  of 
  mountains 
  before 
  us 
  ; 
  simple, 
  both 
  as 
  regards 
  its 
  oro- 
  

   graphic 
  features 
  and 
  the 
  formations 
  composing 
  it. 
  Comparing 
  the 
  

   volcanic 
  strata 
  of 
  this 
  range 
  with 
  those 
  in 
  the 
  district 
  of 
  1874, 
  we 
  find 
  

   that 
  they 
  correspond 
  very 
  well. 
  No. 
  1 
  is 
  not 
  developed 
  at 
  any 
  locality 
  

   here. 
  No. 
  2 
  occurs 
  along 
  the 
  eastern 
  base 
  of 
  the 
  mountains, 
  and, 
  extend- 
  

   ing 
  from 
  there 
  westward, 
  underlies 
  the 
  higher 
  numbers. 
  No. 
  3 
  is 
  by 
  far 
  

   the 
  most 
  prominently 
  developed, 
  attaining 
  in 
  the 
  range 
  a 
  greater 
  thick- 
  

   ness 
  than 
  anywhere 
  west 
  of 
  it. 
  In 
  its 
  detail 
  features, 
  it 
  compares 
  very 
  

   well 
  with 
  the 
  i)arallel 
  number 
  of 
  the 
  Uncompahgre 
  group, 
  so 
  far 
  as 
  

   weathering 
  and 
  mineralogical 
  constitution 
  is 
  concerned. 
  Above 
  it, 
  we 
  

   find 
  the 
  often-mentioned 
  conglomerate. 
  This 
  occurs, 
  too, 
  in 
  the 
  western 
  

   regions, 
  more 
  particularly 
  in 
  Dr. 
  Peale's 
  district, 
  at 
  the 
  base 
  of 
  the 
  bluffs 
  

   leading 
  from 
  the 
  high 
  Uncompahgre 
  group 
  toward 
  the 
  Gunnison 
  River. 
  

   Its 
  first 
  considerable 
  development 
  in 
  our 
  district 
  is 
  found 
  south 
  of 
  the 
  

   Alamosa, 
  and 
  from 
  there 
  continues 
  on 
  to 
  the 
  Conejos. 
  At 
  the 
  southern 
  

   end 
  of 
  the 
  range 
  (*. 
  e., 
  so 
  far 
  as 
  contained 
  in 
  this 
  district), 
  where 
  the 
  

   metamorphic 
  rocks 
  make 
  their 
  appearance, 
  it 
  occurs 
  mainly 
  in 
  the 
  

   caiions, 
  not 
  reaching 
  up 
  higher 
  into 
  the 
  mountains. 
  On 
  the 
  entire 
  

   western 
  slope 
  of 
  the 
  range 
  the 
  conglomerate 
  is 
  well 
  represented, 
  varying 
  

   in 
  thickness, 
  however, 
  from 
  600 
  to 
  1,300 
  feet. 
  Its 
  geognostic 
  position 
  

   is 
  constant, 
  overlying 
  the 
  lower 
  beds 
  of 
  No. 
  3, 
  underlying 
  its 
  highest 
  

   ones 
  and 
  the 
  " 
  nondescrix)t 
  " 
  strata 
  described 
  from 
  station 
  21 
  of 
  1874. 
  

   No. 
  4 
  is 
  but 
  rarely 
  found, 
  only 
  on 
  some 
  of 
  the 
  highest 
  peaks 
  of 
  the 
  range. 
  

   Basalt 
  is 
  met 
  with 
  in 
  large 
  masses, 
  of 
  uniform 
  character. 
  The 
  great 
  

   flow 
  that 
  covers 
  the 
  western 
  edge 
  of 
  San 
  Luis 
  Valley, 
  and 
  the 
  adjoining 
  

   bluiJs 
  and 
  plateaus, 
  like 
  a 
  huge 
  black 
  sheet, 
  is 
  one 
  of 
  great 
  interest, 
  

   both 
  as 
  regards 
  its 
  origin 
  and 
  the 
  causes 
  for 
  its 
  singularly 
  equal 
  dis- 
  

   tribution. 
  

  

  Touching 
  the 
  origin 
  of 
  the 
  entire 
  volcanic 
  mass 
  composing 
  the 
  Sa- 
  

   watch 
  Range,! 
  have 
  come 
  to 
  the 
  conclusion 
  that 
  it 
  is 
  but 
  the 
  continuation 
  

   of 
  the 
  group 
  to 
  the 
  northwest. 
  At 
  no 
  point 
  throughout 
  the 
  range 
  was 
  

   any 
  evidence 
  collected 
  that 
  might 
  lead 
  to 
  an 
  inference 
  regarding 
  any 
  

   particular 
  region 
  within 
  its 
  limits 
  as 
  one 
  of 
  trachytic 
  eruption. 
  The 
  

   highest 
  mountains, 
  as 
  well 
  as 
  the 
  plateaus 
  and 
  bluffs, 
  show 
  so 
  decided 
  

   a 
  stratification 
  that 
  they 
  cannot 
  be 
  regarded 
  otherwise 
  than 
  as 
  having 
  

   been 
  formed 
  by 
  a 
  series 
  of 
  flows. 
  After 
  the 
  first 
  flows 
  had 
  subsided, 
  a 
  

   large 
  quantity 
  of 
  water 
  must 
  have 
  invaded 
  the 
  region, 
  an 
  evidence 
  of 
  

   which 
  is 
  to-day 
  furnished 
  by 
  the 
  existence 
  and 
  distribution 
  of 
  the 
  con- 
  

   glomerate. 
  At 
  numerous 
  localities 
  it 
  shows 
  proof 
  of 
  having 
  been 
  depos- 
  

   ited 
  by 
  water, 
  not 
  only 
  by 
  the 
  marks 
  of 
  stratification, 
  but 
  also 
  by 
  the 
  

   arrangement 
  of 
  the 
  large 
  and 
  small 
  bowlders. 
  Frequently 
  a 
  thin 
  

   stratum 
  can 
  be 
  found, 
  composed 
  almost 
  entirely 
  of' 
  sand, 
  while 
  at 
  other 
  

   places 
  nearly 
  all 
  the 
  bowlders 
  are 
  large, 
  with 
  the 
  interstices 
  filled 
  in 
  

   with 
  gravel 
  and 
  sand. 
  It 
  is 
  clear 
  that 
  a 
  large 
  amount 
  of 
  erosion 
  from 
  

   trachytic 
  beds 
  must 
  have 
  taken 
  place 
  to 
  produce 
  this 
  extensive 
  deposit. 
  

   So 
  far 
  as 
  my 
  observations 
  go, 
  nothing 
  but 
  trachyte 
  and 
  trachytic 
  sand 
  

   make 
  up 
  the 
  conglomerate 
  ; 
  therefore, 
  if 
  these 
  observations 
  are 
  sufficiently 
  

   complete, 
  the 
  material 
  for 
  its 
  formation 
  must 
  have 
  been 
  furnished 
  entirely 
  

   by 
  older 
  volcanic 
  beds. 
  Although 
  it 
  would 
  be 
  a 
  futile 
  attempt 
  to 
  make 
  any 
  

   suggestions 
  as 
  to 
  the 
  courses 
  taken 
  by 
  the 
  drainage 
  of 
  that 
  country 
  afterr 
  

   the 
  eruptions 
  of 
  the 
  oldest 
  volcanic 
  strata, 
  a 
  few 
  hints 
  are 
  furnished 
  by 
  

   the 
  outcropping 
  of 
  the 
  older 
  metamorphic 
  rocks. 
  From 
  their 
  present 
  

  

  