﻿356 
  REPORT 
  UNITED 
  STATES 
  GEOLOGICAL 
  SURVEY. 
  

  

  II 
  

  

  Aside 
  from 
  the 
  temperature 
  there 
  is 
  of 
  course 
  great 
  difference 
  in 
  the 
  

   climates 
  of 
  those 
  western 
  cities 
  as 
  compared 
  with 
  the 
  east. 
  The 
  rain- 
  

   fall 
  is 
  not 
  more 
  than 
  one-third 
  that 
  of 
  the 
  Atlantic 
  coast, 
  cities 
  and 
  the 
  

   general 
  dryness 
  of 
  the 
  atmosphere 
  in 
  a 
  like 
  proportion. 
  

  

  The 
  general 
  rule 
  of 
  decrease 
  of 
  three 
  degrees 
  of 
  temperature 
  per 
  1,000 
  

   feet 
  of 
  altitude, 
  though 
  far 
  from 
  an 
  unvarying 
  law, 
  may 
  give 
  an 
  approxi- 
  

   mation 
  to 
  the 
  general 
  temperature 
  of 
  the 
  divide, 
  and 
  give 
  an 
  annual 
  

   roean 
  of 
  some 
  43°, 
  something 
  less 
  than 
  that 
  of 
  Buffalo, 
  K 
  Y., 
  and 
  nearly 
  

   equal 
  to 
  that 
  of 
  Milwaukee, 
  Wis. 
  

  

  By 
  an 
  examination 
  of 
  the 
  table 
  it 
  will 
  be 
  seen 
  that 
  Canon 
  City 
  at 
  

   about 
  the 
  same 
  latitude 
  as 
  Washington, 
  but 
  with 
  altitude 
  of 
  5,300 
  feet 
  

   above 
  it, 
  has 
  practically 
  the 
  same 
  temperature. 
  Eelative 
  humidities 
  

   would 
  show 
  an 
  immensely 
  greater 
  evaporation 
  at 
  the 
  former 
  place. 
  

   CaSon, 
  though 
  less 
  than 
  a 
  degree 
  of 
  latitude 
  south 
  of 
  Denver 
  and 
  at 
  

   nearly 
  the 
  same 
  altitude, 
  has 
  a 
  much 
  warmer 
  climate, 
  averaging 
  some 
  

   ten 
  degrees. 
  This 
  is 
  owing 
  greatly 
  to 
  the 
  peculiarly 
  protected 
  position 
  

   of 
  the 
  city. 
  It 
  lies 
  in 
  a 
  deep 
  bay 
  in 
  the 
  mountain 
  base, 
  aad 
  is 
  thor- 
  

   oughly 
  surrounded 
  on 
  three 
  sides 
  by 
  mountains 
  ; 
  its 
  only 
  exposure 
  being 
  

   toward 
  the 
  southeast. 
  Denver 
  temperatures 
  very 
  nearly 
  approximate 
  \ 
  

   those 
  of 
  Chicago, 
  and 
  slightly 
  lower 
  than 
  New 
  York, 
  and 
  slightly 
  higher 
  

   than 
  Colorado 
  Springs. 
  Colorado 
  Springs, 
  though 
  lying 
  a 
  degree 
  south 
  

   of 
  Denver, 
  is 
  nearly 
  1,000 
  feet 
  above 
  it 
  in 
  altitude, 
  readily 
  accounting 
  for 
  \ 
  

   the 
  increased 
  cold. 
  Other 
  years' 
  observations, 
  published 
  by 
  the 
  Signal 
  

   Office, 
  retain 
  nearly 
  the 
  same 
  relations 
  between 
  the 
  temperatures 
  of 
  

   these 
  cities, 
  making 
  this 
  table 
  a 
  fair 
  criterion 
  of 
  what 
  more 
  extended 
  J 
  

   observations 
  would 
  tend 
  to 
  show. 
  

  

  With 
  this 
  slight 
  discussion 
  of 
  the 
  climate 
  of 
  the 
  district 
  I 
  will 
  close 
  

   the 
  consideration 
  of 
  this 
  portion 
  of 
  the 
  work, 
  leaving 
  to 
  a 
  study 
  of 
  the 
  

   maps 
  of 
  the 
  survey 
  the 
  more 
  careful 
  understanding 
  of 
  its 
  whole 
  topo- 
  

   graphical 
  features. 
  

  

  Dr. 
  Hayden, 
  Dr. 
  Peale, 
  and 
  Mr. 
  Holmes 
  have 
  all 
  written 
  of 
  it 
  in 
  their 
  

   geographical 
  reports, 
  while 
  a 
  great 
  amount 
  of 
  Colorado 
  letter- 
  writing 
  

   has 
  been 
  devoted 
  to 
  this 
  belt 
  of 
  country 
  which 
  forms 
  the 
  line 
  of 
  junc- 
  

   tion 
  of 
  the 
  mountains 
  and 
  the 
  plains. 
  

  

  The 
  second 
  and 
  main 
  portion 
  of 
  our 
  district, 
  lying 
  west 
  of 
  the 
  one 
  

   hundred 
  and 
  eighth 
  meridian, 
  with 
  boundaries 
  as 
  given 
  in 
  the 
  first 
  part 
  

   of 
  this 
  paper, 
  was 
  entered 
  on 
  the 
  29th 
  of 
  June, 
  the 
  first 
  topographical 
  

   station 
  being 
  made 
  on 
  the 
  east 
  side 
  of 
  the 
  La 
  Plata 
  Eiver, 
  and 
  looking 
  

   down 
  and 
  across 
  it 
  to 
  the 
  south 
  and 
  west. 
  

  

  This 
  southwestern 
  district 
  is 
  divided 
  naturally 
  into 
  two 
  portions 
  by 
  

   its 
  two 
  distinct 
  drainage 
  systems 
  ; 
  the 
  first, 
  that 
  of 
  the 
  San 
  Juan, 
  and 
  

   second 
  of 
  the 
  Dolores. 
  The 
  San 
  Juan 
  drains 
  the 
  whole 
  southern 
  and 
  

   western 
  portions 
  and 
  empties 
  its 
  waters 
  into 
  the 
  Colorado 
  Eiver, 
  some- 
  

   thing 
  more 
  than 
  a 
  hundred 
  miles 
  below 
  the 
  junction 
  of 
  the 
  Green 
  and 
  

   Grand. 
  The 
  Dolores 
  drains 
  only 
  the 
  northeastern 
  portion 
  of 
  the 
  

   district. 
  It 
  rises 
  in 
  the 
  southern 
  face 
  of 
  the 
  San 
  Miguel 
  Mountains, 
  

   flows 
  first 
  to 
  the 
  south 
  and 
  southwest 
  for 
  about 
  34 
  miles, 
  and 
  then 
  turn- 
  

   ing 
  sharply 
  back 
  flows 
  in 
  a 
  northwesterly 
  direction 
  till 
  it 
  joins 
  the 
  

   Grand, 
  50 
  miles 
  above 
  its 
  junction 
  with 
  the 
  Green. 
  At 
  the 
  bend 
  the 
  

   Dolores 
  would 
  require 
  a 
  cut 
  of 
  less 
  than 
  200 
  feet 
  in 
  depth 
  to 
  turn 
  its 
  

   waters 
  into 
  the 
  San 
  Juan, 
  in 
  what, 
  from 
  the 
  configuration 
  of 
  the 
  country, 
  

   would 
  seem 
  decidedly 
  to 
  be 
  the 
  natural 
  course 
  of 
  the 
  drainage. 
  But 
  

   the 
  river, 
  planned 
  in 
  other 
  times, 
  comes 
  from 
  a 
  deep 
  canon 
  out 
  to 
  find 
  

   this 
  low 
  divide, 
  and 
  then, 
  disregarding 
  the 
  tempting 
  offer, 
  plunges 
  again 
  

   into 
  a 
  narrow 
  gorge 
  and 
  finally 
  loses 
  it 
  in 
  the 
  Green 
  150 
  miles 
  from 
  

   where 
  the 
  San 
  Juan 
  finds 
  its 
  mouth. 
  

  

  