﻿HOLMES.] 
  DRAINAGE 
  OF 
  THE 
  GREAT 
  SAGE-PLAIN. 
  265 
  

  

  river 
  its 
  present 
  course 
  in 
  the 
  simplest 
  manner, 
  and 
  then 
  make 
  out, 
  if 
  

   possible, 
  the 
  subsequent 
  changes 
  that 
  would 
  be 
  necessary 
  to 
  produce 
  

   the 
  present 
  extraor-diuary 
  condition. 
  Having 
  the 
  river 
  once 
  laid 
  down 
  

   in 
  its 
  jjresent 
  course, 
  we 
  have 
  but 
  to 
  suppose 
  a 
  gradual 
  elevation 
  to 
  the 
  

   north 
  and 
  northwest 
  — 
  an 
  elevation 
  not 
  so 
  rapid 
  as 
  to 
  turn 
  the 
  river 
  back 
  

   upon 
  itself 
  and 
  cause 
  it 
  to 
  seek 
  an 
  outlet 
  in 
  another 
  direction, 
  but 
  nearly 
  

   so 
  — 
  and 
  we 
  overcome 
  the 
  greatest 
  difficulty. 
  The 
  problems 
  of 
  the 
  slop- 
  

   ing 
  plain 
  and 
  the 
  unequally 
  apportioned 
  drainage 
  are 
  easily 
  solved. 
  

  

  While 
  this 
  gradual 
  change 
  of 
  level 
  was 
  taking 
  place, 
  and 
  the 
  river, 
  

   with 
  strong 
  voluQie 
  of 
  water, 
  was 
  succeeding 
  in 
  cutting 
  its 
  bed 
  down 
  as 
  

   fast 
  as 
  the 
  iold 
  rose, 
  the 
  tributaries, 
  with 
  very 
  weak 
  erosive 
  powers, 
  

   were 
  undergoing 
  a 
  gradual 
  but 
  important 
  change. 
  The 
  southward- 
  

   flowing 
  streams 
  would 
  constantly 
  be 
  increasing 
  in 
  length 
  and 
  impor- 
  

   tance, 
  owing 
  to 
  the 
  assistance 
  given 
  to 
  the 
  degrading 
  influences 
  by 
  

   increased 
  slope, 
  while 
  the 
  northward-flowing 
  ones, 
  which 
  were 
  doubtless 
  

   originally 
  equal 
  to 
  the 
  southward, 
  would 
  be 
  constantly 
  losing 
  ground 
  

   on 
  account 
  of 
  decreased 
  slope. 
  Thus 
  on 
  the 
  divide 
  between 
  the 
  l)olores 
  

   and 
  San 
  Juan, 
  which 
  was 
  doubtless 
  originally 
  midway 
  between 
  the 
  two 
  

   streams, 
  an 
  unequal 
  war 
  would 
  be 
  waged. 
  As 
  the 
  slope 
  increased 
  the 
  

   southern 
  streams 
  grew 
  stronger 
  and 
  the 
  northern 
  weaker, 
  so 
  that 
  the 
  

   divide 
  would 
  be 
  driven 
  to 
  the 
  north 
  with 
  constantly 
  accelerated 
  

   rapidity. 
  But 
  it 
  is 
  evident 
  that 
  a 
  more 
  marked 
  inequality 
  would 
  take 
  

   place 
  when 
  the 
  first 
  hard 
  stratum 
  of 
  the 
  Dakota 
  sandstones 
  was 
  reached. 
  

   The 
  southern 
  tributaries 
  of 
  the 
  Dolores, 
  as 
  will 
  be 
  easily 
  seen 
  by 
  the 
  

   sections 
  in 
  Plate 
  XLIII, 
  would 
  first 
  encounter 
  these 
  compact 
  beds 
  on 
  the 
  

   very 
  brink 
  of 
  the 
  river, 
  and 
  thus 
  the 
  already 
  weak 
  eroding 
  forces 
  would 
  

   almost 
  cease 
  to 
  act, 
  for 
  however 
  much 
  of 
  the 
  friable 
  shales 
  might 
  be 
  

   disintegrated 
  and 
  sink 
  into 
  the 
  stream-courses, 
  the 
  constantly-rising 
  

   edge 
  of 
  sandstone 
  along 
  the 
  river-bank 
  would 
  act 
  as 
  a 
  dam 
  to 
  prevent 
  

   its 
  being 
  carried 
  into 
  the 
  river. 
  Meantime 
  the 
  tributaries 
  of 
  the 
  San 
  

   Ju&n, 
  still 
  flowing 
  in 
  the 
  shales, 
  would 
  keep 
  on 
  deepening 
  and 
  increasing 
  

   in 
  slope; 
  would 
  keep 
  on 
  driving 
  the 
  divide 
  to 
  the 
  north 
  until 
  they 
  had 
  

   swept 
  the 
  great 
  sloping 
  plain 
  clear 
  of 
  softer 
  deposits, 
  left 
  it 
  a 
  smooth 
  

   surface 
  of 
  solid 
  rock, 
  and 
  wrested 
  it 
  entirely 
  from 
  the 
  tributaries 
  of 
  the 
  

   Dolores 
  up 
  to 
  the 
  very 
  brink 
  of 
  that 
  river. 
  

  

  From 
  the 
  summit 
  of 
  Ute 
  Peak 
  a 
  very 
  complete 
  view 
  of 
  this 
  region 
  

   is 
  obtained. 
  In 
  the 
  foreground, 
  at 
  the 
  very 
  base 
  of- 
  the 
  mountain, 
  is 
  

   the 
  caiion 
  of 
  the 
  McElmo. 
  Opening 
  into 
  it 
  from 
  the 
  north 
  are 
  a 
  great 
  

   number 
  of 
  deep, 
  precipitous 
  side 
  canons, 
  which 
  reach 
  back 
  8 
  or 
  10 
  

   miles 
  into 
  the 
  sage-plain. 
  At 
  this 
  distance 
  they 
  become 
  shallow, 
  and 
  

   finally 
  fade 
  out; 
  so 
  that 
  next 
  to 
  the 
  Dolores 
  there 
  is 
  a 
  long, 
  smooth 
  

   slope. 
  Beyond 
  the 
  Dolojes 
  this 
  slope 
  continues, 
  as 
  previously 
  described. 
  

   Along 
  this 
  slope 
  the 
  canon 
  of 
  the 
  Dolores 
  can 
  be 
  distinctly 
  traced, 
  ap- 
  

   parently 
  first 
  descending 
  from 
  the 
  northeast 
  to 
  the 
  great 
  bend 
  at 
  the 
  

   south, 
  and 
  then 
  ascending 
  again 
  to 
  the 
  northwest. 
  

  

  The 
  various 
  branches 
  can 
  be 
  traced 
  back 
  to 
  the 
  north 
  and 
  east 
  (see 
  

   Plates 
  XXXVI 
  and 
  XLII). 
  The 
  northern 
  branch 
  drains 
  the 
  southern 
  

   faces 
  of 
  the 
  San 
  Miguel 
  Mouutains. 
  The 
  south 
  fork, 
  or 
  Bear 
  Eiver, 
  

   drains 
  the 
  high 
  divide 
  region 
  between 
  the 
  San 
  Miguel 
  and 
  La 
  Plata 
  

   Mountains, 
  including 
  the 
  Bear 
  Eiver 
  Mountains, 
  and 
  the 
  Lost 
  Cailou 
  

   comes 
  down 
  from 
  the 
  western 
  slope 
  of 
  the 
  La 
  Plata 
  Mountains. 
  These 
  

   are 
  the 
  only 
  tributaries 
  of 
  the 
  Dolores 
  in 
  this 
  region. 
  It 
  has 
  no 
  other 
  

   tributary 
  between 
  the 
  Lost 
  Caiion 
  and 
  the 
  San 
  Miguel, 
  a 
  distance 
  of 
  75 
  

   mdes. 
  Far 
  to 
  the 
  northwest 
  a 
  great 
  notch 
  can 
  be 
  seen 
  in 
  the 
  sky-line 
  

   where 
  the 
  Dolores, 
  in 
  its 
  northern 
  course, 
  cuts 
  through 
  the 
  northern 
  

   edge 
  of 
  the 
  plateau. 
  Beyond 
  this 
  notch 
  the 
  river 
  flows 
  for 
  a 
  long 
  dis- 
  

  

  