﻿ENDLicH.] 
  SANGEE 
  DE 
  CEISTO 
  CARBONIFEROUS. 
  121 
  

  

  fragments 
  of 
  argillite 
  and 
  micaceous 
  schists, 
  will 
  be 
  noticed. 
  ISTot 
  until 
  

   after 
  leaving 
  timber-line, 
  however, 
  can 
  the 
  fall 
  extent 
  of 
  the 
  metamor- 
  

   phosis 
  be 
  appreciated, 
  Numerous 
  dikes 
  of 
  a 
  rhj'olitic 
  trachyte 
  traverse 
  

   the 
  sandstone 
  strata, 
  and 
  on 
  either 
  side 
  of 
  them 
  the 
  changes 
  produced 
  

   by 
  heat 
  under 
  pressure 
  are 
  evident. 
  Eed 
  shales 
  are 
  changed 
  into 
  ma- 
  

   roon-colored, 
  hard 
  argillites, 
  uncomfortable 
  to 
  walk 
  on. 
  The 
  quartzitic 
  

   sandstones 
  have 
  turned 
  into 
  red 
  granular 
  quartzites, 
  while 
  the 
  argilhice- 
  

   ous 
  ones 
  are 
  now 
  a 
  typical 
  granite. 
  Schists 
  are 
  rare, 
  but 
  still 
  occur, 
  proba- 
  

   bly 
  being 
  the 
  result 
  of 
  highly 
  argillaceous 
  sandstones. 
  Following 
  along 
  

   the 
  strata, 
  beyond 
  the 
  influence 
  of 
  the 
  volcanic 
  heat, 
  these 
  same 
  rocks 
  

   return 
  by 
  gradation 
  to 
  their 
  original 
  character. 
  At 
  times 
  very 
  narrow 
  

   dikes 
  only, 
  or 
  ramifications 
  of 
  larger 
  ones, 
  can 
  be 
  found, 
  and 
  the 
  ex- 
  

   tent 
  of 
  the 
  material 
  changed 
  by 
  them 
  will 
  be 
  in 
  proportion 
  to 
  their 
  size, 
  

   Nearing 
  the 
  summit, 
  which 
  is 
  entirely 
  volcanic-, 
  the 
  metamorphosing 
  

   influences 
  are 
  found 
  to 
  have 
  had 
  full 
  sway. 
  Hard 
  fragments 
  of 
  the 
  

   changed 
  rocks 
  have 
  a 
  ring 
  almost 
  like 
  that 
  of 
  phonolite, 
  weather 
  in 
  

   slabs, 
  and 
  show 
  indications 
  of 
  columnar 
  structure. 
  On 
  the 
  ridge 
  and 
  

   on 
  the 
  sides 
  of 
  the 
  mountain 
  they 
  stand 
  out 
  prominently, 
  resisting 
  more 
  

   successfully 
  than 
  their 
  unchanged 
  surroundings 
  the 
  destroying 
  notion 
  

   of 
  atmospheric 
  agents. 
  There 
  are 
  few 
  localities, 
  ])robably, 
  to 
  be 
  found, 
  

   where 
  this 
  important 
  branch 
  of 
  chemical 
  geology 
  is 
  so 
  thoroughly 
  illus- 
  

   trated, 
  and 
  at 
  the 
  same 
  time 
  so 
  accessible. 
  It 
  is 
  to 
  be 
  regretted 
  that 
  

   during 
  the 
  time 
  of 
  our 
  ascent 
  snow 
  covered 
  a 
  large 
  portion 
  of 
  the 
  

   mountain, 
  and 
  examinations 
  could 
  be 
  made 
  only 
  with 
  diiiiculty. 
  

  

  From 
  the 
  Spanish 
  Peaks 
  the 
  red 
  sandstone 
  continues 
  along 
  the 
  east- 
  

   ern 
  side 
  of 
  the 
  Sangre 
  de 
  Cristo 
  Eange, 
  reaching 
  just 
  to 
  the 
  base 
  of 
  the 
  

   mountains 
  where 
  the 
  Cretaceous 
  beds 
  begin. 
  In 
  nothing 
  does 
  it 
  vary 
  

   from 
  the 
  occurrences 
  farther 
  north. 
  Its 
  thickness 
  remains 
  constant, 
  

   about 
  2,000 
  feet, 
  and 
  its 
  dip 
  is 
  to 
  the 
  eastward, 
  perfectly 
  regular. 
  Sta- 
  

   tion 
  124 
  is 
  located 
  on 
  it 
  near 
  the 
  middle 
  fork 
  of 
  the 
  Purgatory, 
  at 
  an 
  ele- 
  

   vation 
  of 
  9,824 
  feet. 
  North 
  of 
  station 
  111 
  (Costilla 
  Peak) 
  it 
  is 
  covered 
  

   in 
  part 
  by 
  trachyte, 
  but 
  only 
  for 
  a 
  short 
  distance. 
  At 
  this 
  point 
  a 
  j)rob- 
  

   lem 
  presents 
  itself, 
  similar 
  to 
  that 
  near 
  station 
  121. 
  I 
  have 
  alluded 
  to 
  

   the 
  long 
  outcrop 
  of 
  the 
  white 
  sandstone, 
  following 
  a 
  line 
  about 
  north 
  to 
  

   south, 
  which 
  is 
  broken 
  at 
  times, 
  for 
  which, 
  however, 
  the 
  connection 
  can 
  

   always 
  readily 
  be 
  established. 
  Tbis 
  sandstone 
  continues 
  south 
  as 
  far 
  

   as 
  the 
  northern 
  base 
  of 
  Costilla 
  Peak, 
  About 
  ten 
  miles 
  north 
  of 
  the 
  

   peak 
  it 
  stands 
  perfectly 
  vertical, 
  and 
  going 
  farther 
  south 
  gradually 
  

   turns 
  to 
  a 
  western 
  dip, 
  while 
  the 
  tendency 
  of 
  its 
  dip 
  up 
  to 
  that 
  j^ointhas 
  

   been 
  an 
  easterly 
  one. 
  At 
  the 
  same 
  time 
  the 
  strata 
  of 
  red 
  sandstone, 
  

   having 
  a 
  total 
  thickness 
  of 
  about 
  1,800 
  to 
  2,000 
  feet 
  there, 
  follow 
  the 
  

   same 
  course 
  and 
  dip 
  to 
  the 
  westward, 
  until 
  near 
  Costilla 
  Peak 
  they 
  

   dip 
  but 
  about 
  35° 
  from 
  the 
  horizontal. 
  Near 
  this 
  peak 
  the 
  Carbonifer- 
  

   ous 
  strata 
  end 
  abruptly 
  against 
  the 
  granite, 
  but 
  the 
  end 
  of 
  the 
  white 
  

   sandstone 
  cannot 
  be 
  seen. 
  

  

  A 
  sketch 
  made 
  from 
  station 
  111, 
  looking 
  northward 
  toward 
  the 
  Span- 
  

   ish 
  Peaks, 
  may 
  give 
  an 
  idea 
  of 
  the 
  general 
  configuration 
  of 
  the 
  country. 
  

   On 
  the 
  west 
  side 
  a 
  continuous 
  ridge 
  (a), 
  composed 
  of 
  red 
  sandstone, 
  runs 
  

   nearly 
  north 
  to 
  south. 
  The 
  dip 
  of 
  this 
  sandstone 
  is 
  to 
  the 
  westward. 
  

   It 
  slopes 
  down, 
  at 
  first 
  rather 
  steeply, 
  then 
  more 
  gently, 
  until 
  the 
  sec- 
  

   ond 
  ridge 
  (b) 
  is 
  formed 
  by 
  the 
  white 
  sandstone 
  in 
  question, 
  Near 
  the 
  

   station 
  this 
  also 
  has 
  a 
  westerly 
  dip, 
  but 
  some 
  distance 
  off 
  assumes 
  the 
  

   vertical 
  and 
  then 
  steeply 
  dips 
  to 
  the 
  east, 
  A 
  narrow, 
  long 
  ^^lley 
  sepa- 
  

   rates 
  this 
  ridge 
  from 
  the 
  third 
  one 
  (c), 
  which, 
  however, 
  is 
  formed 
  by 
  

   sandstones 
  by 
  far 
  younger 
  thau 
  any 
  of 
  the 
  preceding, 
  A 
  short 
  distance 
  

   from 
  Costilla 
  Peak 
  there 
  rises 
  in 
  the 
  middle 
  of 
  this 
  valley 
  acomxjaratively 
  

  

  