﻿ENDLicH.-j 
  SA 
  WATCH 
  RANGE 
  BASAJLT. 
  163 
  

  

  e. 
  Where 
  the 
  compression 
  goes 
  so 
  far 
  as 
  to 
  produce 
  a 
  decided 
  lamin- 
  

   ation. 
  On 
  the 
  suriace 
  of 
  fracture, 
  which 
  latter 
  occurs 
  only 
  in 
  the 
  direc- 
  

   tion 
  of 
  the 
  longitudinal 
  axes 
  of 
  the 
  vesicles, 
  it 
  has 
  an 
  appearance 
  similar 
  

   to 
  that 
  of 
  the 
  surface 
  of 
  a 
  palm-leaf. 
  The 
  vesicles 
  no 
  longer 
  remain 
  as 
  

   such, 
  and 
  are 
  only 
  indicated 
  by 
  the 
  quasi 
  cleavage-planes 
  of 
  the 
  rock. 
  

  

  /. 
  Shows 
  no 
  segregated 
  minerals 
  whatever, 
  and 
  is 
  as 
  porous 
  as 
  a 
  

   sponge. 
  The 
  vesicles 
  are 
  small, 
  averaging 
  I'"™ 
  in 
  diameter. 
  

  

  g. 
  Paste 
  microcrystalllne, 
  its 
  structure 
  much 
  obscured 
  by 
  decomposi- 
  

   tion. 
  Compact, 
  no 
  vesicles. 
  Color, 
  mottled 
  red-brown 
  and 
  black. 
  

   Small 
  particles 
  of 
  olivine 
  are 
  distinguishable, 
  although 
  decomposed. 
  

   This 
  is 
  essentially 
  the 
  variety 
  c, 
  without 
  vesicles 
  and 
  a 
  changed 
  color, 
  

   the 
  result 
  of 
  higher 
  oxidation 
  of 
  the 
  magnetite. 
  

  

  h. 
  Same 
  as 
  g 
  in 
  paste. 
  Color, 
  reddish 
  drab. 
  Minute, 
  irregular 
  cavi- 
  

   ties, 
  produced 
  by 
  decomposition 
  of 
  certain 
  mineral 
  constituents. 
  Oliv- 
  

   ine 
  Inclosures 
  reaching 
  a 
  diameter 
  of 
  2™™. 
  This 
  is 
  a 
  still 
  further 
  pro- 
  

   gressed 
  product 
  of 
  decomposition. 
  

  

  i. 
  Very 
  much 
  like 
  /. 
  Color, 
  greyish 
  brown, 
  thoroughly 
  vesicular. 
  

   IS'ot 
  only 
  are 
  the 
  small 
  vesicles 
  found 
  as 
  in/, 
  but 
  large 
  ones 
  occur, 
  show- 
  

   ing 
  a 
  glazed 
  surface. 
  All 
  of 
  them 
  have 
  been 
  more 
  or 
  less 
  drawn 
  out. 
  

   In 
  its 
  texture 
  it 
  closely 
  resembles 
  jjumice. 
  

  

  Station 
  104. 
  Basalt. 
  

  

  a. 
  Paste, 
  microcrystalllne; 
  color, 
  black. 
  Minute 
  crystals 
  of 
  feldspar 
  

   and 
  finely 
  distributed 
  olivine 
  give 
  the 
  rock 
  a 
  glassy 
  luster. 
  Innumer- 
  

   able 
  small 
  vesicles. 
  Some 
  larger 
  ones 
  are 
  scattered 
  throughout. 
  The 
  

   latter 
  are 
  filled 
  with 
  either 
  crystalline, 
  crystallized, 
  or 
  amorphous 
  carbon- 
  

   ate 
  of 
  lime. 
  I 
  do 
  not 
  regard 
  these 
  amygdules 
  as 
  accidental 
  inclosures,* 
  

   but 
  consider 
  their 
  formation 
  to 
  be 
  a 
  secondary 
  one. 
  Probably 
  it 
  is 
  the 
  

   result 
  of 
  the 
  decomposition 
  of 
  minerals 
  containing 
  lime, 
  which 
  latter 
  was 
  

   held 
  in 
  solution 
  by 
  water 
  containing 
  carbonic-acid 
  gas, 
  and 
  deposited 
  

   by 
  it 
  in 
  the 
  vesicles 
  upon 
  the 
  loss 
  of 
  this 
  gas. 
  Were 
  the 
  amygdules 
  

   accidental 
  inclosures 
  of 
  limestone, 
  their 
  form 
  would 
  not 
  be 
  regular 
  

   (spheroid) 
  nor 
  would 
  they 
  consist 
  of 
  calcite, 
  but 
  of 
  marble. 
  Experi- 
  

   ments 
  have 
  shown 
  that 
  pure 
  limestone 
  changes 
  into 
  marble, 
  not 
  crystal- 
  

   lized 
  calcite, 
  upon 
  being 
  subjected 
  to 
  heat 
  with 
  exclusion 
  of 
  air. 
  

  

  Station 
  99. 
  Basalt. 
  

  

  a. 
  Paste, 
  greyish 
  black 
  when 
  fresh, 
  reddish 
  brown 
  when 
  decomposed 
  ; 
  

   crystalline. 
  Crystals 
  of 
  black 
  biotite 
  in 
  minute 
  crystals. 
  Olivine 
  brown. 
  

   Minute 
  vesicles 
  and 
  scattering 
  larger 
  ones, 
  both 
  irregular. 
  

  

  Eecurring 
  again 
  to 
  the 
  headwaters 
  of 
  Eio 
  Conejos, 
  we 
  find 
  that 
  

   this 
  stream 
  rises 
  entirely 
  in 
  a 
  trachytic 
  area. 
  Stations 
  84 
  and 
  87 
  are 
  

   located 
  at 
  the 
  heads 
  of 
  Conejos 
  waters, 
  on 
  the 
  continental 
  divide; 
  

   the 
  latter 
  at 
  an 
  elevation 
  of 
  12,261 
  feet. 
  Here 
  we 
  find 
  evidence 
  of 
  a 
  

   very 
  extensive 
  glacier, 
  which 
  at 
  one 
  time 
  covered 
  the 
  entire 
  plateau 
  

   there, 
  and 
  branching 
  off 
  from 
  the 
  high 
  summit 
  spread 
  itself 
  in 
  several 
  

   courses 
  both 
  toward 
  the 
  east 
  and 
  south. 
  Deep 
  caSons 
  have 
  been 
  cut 
  

   into 
  the 
  volcanic 
  material, 
  some 
  of 
  which 
  are 
  almost 
  inaccessible. 
  A 
  

   hard 
  bed 
  of 
  trachyte 
  forms 
  the 
  highest 
  portions 
  of 
  the 
  plateau 
  trending 
  

   north 
  to 
  south, 
  and 
  overlies 
  the 
  readily-eroded 
  trachytic 
  conglomerates. 
  

   Striation 
  and 
  polishing 
  of 
  the 
  former 
  furnishes 
  indisputable 
  proof 
  of 
  

   the 
  action 
  of 
  moving 
  ice, 
  while 
  the 
  caiions 
  cut 
  into 
  the 
  conglomerate, 
  

   narrow 
  and 
  deep, 
  denote 
  the 
  courses 
  taken 
  by 
  the 
  ice 
  and 
  water 
  after 
  

  

  "Comp. 
  O. 
  Loew. 
  Exijlcratiou 
  aud 
  Survey 
  West 
  of 
  One 
  Hundredth 
  Meridian, 
  1875, 
  

   vol 
  iii, 
  p. 
  642. 
  

  

  