﻿EXDUcii] 
  APPENDIX 
  ANCIENT 
  GLACIERS. 
  217 
  

  

  the 
  efi'ect 
  there 
  observed. 
  On 
  the 
  other 
  hand, 
  the 
  evenness 
  of 
  the 
  val- 
  

   ley, 
  the 
  presence 
  of 
  shallow 
  lakes, 
  and 
  the 
  long-continued 
  appearance 
  

   of 
  this 
  granite, 
  in 
  the 
  same 
  manner., 
  strongly 
  argue 
  for 
  the 
  acceptance 
  

   of 
  glacial 
  action 
  in 
  having 
  thus 
  shaped 
  its 
  surface. 
  Granite 
  decom- 
  

   posing 
  as 
  readily 
  as 
  the 
  one 
  in 
  question 
  does 
  would 
  not 
  retain 
  striation 
  

   for 
  the 
  same 
  length 
  of 
  time 
  as 
  either 
  the 
  hard 
  quartzite 
  or 
  the 
  schists 
  

   would, 
  and 
  it 
  is 
  quite 
  possible, 
  therefore, 
  that 
  the 
  more 
  positive 
  evi- 
  

   dences 
  of 
  moving 
  ice 
  may 
  have 
  been 
  obliterated 
  by 
  the 
  never-ceasing 
  

   activity 
  of 
  atmospheric 
  influences. 
  Traveling 
  farther 
  toward 
  the 
  south, 
  

   the 
  exposed 
  granite 
  increases 
  in 
  quantity 
  until 
  we 
  reach 
  Animas 
  City, 
  

   Erom 
  there 
  downward 
  heavy 
  drift 
  occurs, 
  marking 
  probably 
  the 
  end 
  of 
  

   the 
  ancient 
  glacier, 
  if 
  such 
  it 
  was, 
  as 
  a 
  terminal 
  moraine. 
  This 
  drift 
  is 
  

   composed 
  of 
  the 
  rocks 
  through 
  which 
  a 
  glacier 
  coming 
  from 
  the 
  north 
  

   would 
  have 
  passed. 
  Quartzites, 
  hornblende, 
  and 
  mica-schists, 
  gneiss, 
  

   and 
  granite, 
  each 
  of 
  many 
  varieties, 
  are 
  represented 
  there. 
  Striation 
  

   could 
  not 
  be 
  noticed 
  on 
  any 
  of 
  the 
  specimens 
  examined, 
  but 
  their 
  shape 
  

   was 
  more 
  uniform 
  than 
  i)robably 
  it 
  would 
  have 
  been 
  did 
  they 
  owe 
  their 
  

   transportation 
  for 
  so 
  many 
  miles 
  from 
  the 
  place 
  of 
  their 
  original 
  occur- 
  

   rence 
  to 
  water 
  solely. 
  Taking 
  into 
  consideration 
  all 
  these 
  facts, 
  it 
  seems 
  

   to 
  me 
  that 
  the 
  most 
  rational 
  conclusion 
  to 
  arrive 
  at 
  is, 
  that 
  the 
  glacier 
  

   descending 
  into 
  and 
  partly 
  down 
  the 
  Animas 
  Valley 
  is 
  of 
  older 
  date 
  

   than 
  those 
  observed 
  higher 
  up 
  in 
  the 
  mountains, 
  and 
  those 
  more 
  shel- 
  

   tered 
  from 
  evaporation 
  in 
  the 
  deep 
  cailons 
  of 
  the 
  Quartzite 
  Mountains. 
  

   It 
  does 
  not 
  seem 
  that 
  ice 
  had 
  at 
  these 
  points 
  a 
  very 
  great 
  influence 
  

   upon 
  the 
  configuration 
  of 
  the 
  country. 
  Certain 
  it 
  is, 
  that 
  manj^ 
  of 
  the 
  

   minor 
  details 
  now 
  to 
  be 
  observed 
  owe 
  their 
  existence 
  to 
  it, 
  but 
  the 
  

   main 
  features 
  of 
  the 
  region 
  had 
  been 
  formed 
  before 
  glaciers. 
  

  

  Near 
  the 
  headwaters 
  of 
  Eio 
  Piedra, 
  south 
  of 
  Weeminuche 
  Pass, 
  

   evidences 
  of 
  glacial 
  action 
  can 
  again 
  be 
  observed. 
  Crossing 
  the 
  pass, 
  

   we 
  find 
  trachyte, 
  which 
  soon, 
  however, 
  disappears, 
  permitting 
  the 
  un- 
  

   derlying 
  metamorphic 
  granite 
  to 
  appear. 
  Here 
  rounded 
  bowlders, 
  hav- 
  

   ing 
  been 
  carried 
  from 
  their 
  place 
  of 
  occurrence 
  for 
  several 
  miles, 
  and 
  

   polished 
  metamori)hic 
  rocks 
  along 
  the 
  hill-sides 
  speak 
  for 
  the 
  existence 
  

   of 
  glaciers. 
  Although 
  the 
  proof 
  of 
  their 
  existence 
  is 
  good 
  at 
  the 
  points 
  

   where 
  it 
  was 
  observed, 
  it 
  soon 
  becomes 
  obliterated 
  farther 
  down 
  stream. 
  

   It 
  is 
  i)robable, 
  therefore, 
  that 
  the 
  ice-fields 
  here 
  were 
  of 
  but 
  small 
  ex- 
  

   tent. 
  They 
  evidently 
  carried 
  bowlders 
  of 
  large 
  size 
  with 
  them 
  and 
  

   deposited 
  them 
  all 
  along 
  their 
  route. 
  This 
  leads 
  me 
  to 
  conclude 
  that 
  

   the 
  size 
  of 
  the 
  glaciers 
  was 
  a 
  variable 
  one, 
  changing, 
  perhaps, 
  with 
  the 
  

   mean 
  temperature 
  of 
  the 
  cold 
  seasons. 
  

  

  Near 
  stations 
  36 
  and 
  37 
  the 
  remains 
  of 
  old 
  glaciers 
  are 
  very 
  easily 
  

   recognized, 
  as 
  also 
  the 
  influence 
  that 
  was 
  brought 
  to 
  bear 
  on 
  the 
  shap- 
  

   ing 
  of 
  the 
  water-courses. 
  A 
  map 
  showing 
  the 
  relative 
  conditions 
  of 
  

   the 
  region 
  is 
  annexed. 
  One 
  of 
  the 
  main 
  branches 
  of 
  the 
  Piedra 
  

   (\Yeeminuche 
  Creek) 
  flows 
  a 
  little 
  east 
  of 
  south, 
  about 
  two 
  miles 
  west 
  

   of 
  station 
  36. 
  It 
  runs 
  first 
  through 
  an 
  area 
  of 
  metamorphic 
  granite, 
  

   then 
  through 
  a 
  naj?row 
  strip 
  of 
  Lower 
  Cretaceous, 
  resting 
  upon 
  the 
  for- 
  

   mer, 
  and 
  finally 
  enters 
  a 
  valley 
  about 
  five 
  miles 
  long 
  and 
  a 
  mile 
  wide. 
  

   While 
  evidence 
  of 
  the 
  passage 
  of 
  glaciers 
  was 
  found 
  above 
  the 
  valley, 
  

   this 
  latter 
  it 
  covered 
  entirely 
  by 
  glacial 
  drift. 
  The 
  glacier 
  moved 
  down 
  

   along 
  the 
  course 
  of 
  the 
  stream, 
  depositing 
  on 
  either 
  side 
  lateral 
  mo- 
  

   raines 
  of 
  small 
  extent, 
  while 
  the 
  central 
  portion 
  remained 
  filled 
  with 
  the 
  

   ice. 
  After 
  moving 
  on 
  for 
  about 
  four 
  miles, 
  the 
  glacier 
  made 
  a 
  curve 
  

   to 
  the 
  eastward, 
  but 
  soon 
  changed 
  again 
  to 
  its 
  old 
  course. 
  In 
  the 
  lower 
  

   part 
  of 
  the 
  valley 
  — 
  Cretaceous 
  — 
  we 
  now 
  find 
  deposited 
  the 
  metamorphic 
  

  

  