﻿ENDLicH.] 
  SPANISH 
  PEAKS. 
  129 
  

  

  the 
  same 
  walls 
  tbat 
  caused 
  their 
  present 
  existeuce, 
  lead 
  up 
  to 
  the 
  sharp 
  

   SLiiiimit 
  of 
  the 
  higher 
  peak. 
  " 
  Sentiuels" 
  of 
  volcanic 
  rock 
  are 
  stationed 
  

   outside, 
  rising 
  in 
  their 
  isolated 
  glory, 
  as 
  if 
  to 
  guard 
  the 
  access 
  to 
  the 
  

   center 
  whence 
  they 
  had 
  their 
  origin. 
  An 
  excavation 
  resembling 
  half 
  

   a 
  crater 
  on 
  the 
  southwest 
  slope 
  of 
  the 
  mountain 
  completes 
  the 
  decep- 
  

   tion 
  already 
  conveyed, 
  that 
  we 
  here 
  have 
  a 
  volcanic 
  eruption 
  that 
  

   has 
  left 
  its 
  evidence 
  in 
  the 
  most 
  approved 
  form. 
  East 
  Spanish 
  Peak, 
  

   lower 
  than 
  the 
  other, 
  presents'steeper 
  outlines, 
  more 
  sharply 
  cut 
  slopes 
  

   and 
  ridges, 
  and 
  less 
  of 
  the 
  characteristic 
  dike-walls 
  than 
  its 
  neighbor. 
  

   Both 
  are 
  beautiful 
  peaks, 
  in 
  form 
  as 
  well 
  as 
  in 
  their 
  geological 
  features. 
  

  

  In 
  speaking 
  of 
  the 
  Carboniferous, 
  it 
  has 
  been 
  stated 
  that 
  the 
  main 
  

   body 
  of 
  the 
  mountain 
  is 
  composed 
  of 
  red 
  sandstone, 
  that 
  has 
  been 
  altered 
  

   by 
  heat, 
  so 
  as 
  to 
  produce 
  a 
  number 
  of 
  species 
  of 
  metamorphic 
  rocks. 
  

   Ascending 
  the 
  western 
  peak 
  from 
  the 
  south, 
  we 
  pass 
  first 
  over 
  the 
  red 
  

   sandstones, 
  until, 
  near 
  timber-line, 
  we 
  find 
  the 
  first 
  evidence 
  of 
  larger 
  

   masses 
  of 
  volcanic 
  rock. 
  Fragments 
  of 
  numerous 
  varieties 
  of 
  trachyte 
  

   and 
  rhyolitic 
  trachyte 
  lay 
  scattered 
  around 
  in 
  great 
  profusion. 
  Vertical 
  

   places 
  are 
  seen 
  along 
  the 
  ridge 
  we 
  propose 
  to 
  climb, 
  and 
  we 
  find 
  upon 
  

   reaching 
  them 
  that 
  they 
  are 
  caused 
  by 
  the 
  intersecting 
  dikes. 
  These 
  

   are 
  from 
  2 
  to 
  GO 
  feet 
  in 
  thickness, 
  and 
  not 
  unfrequently 
  extend 
  from 
  

   near 
  the 
  summit 
  down 
  into 
  the 
  valley 
  for 
  several 
  miles. 
  All 
  the 
  strata 
  

   in 
  their 
  immediate 
  neighborhood 
  have 
  been 
  baked, 
  iritted, 
  and 
  com- 
  

   i:)letely 
  changed. 
  Near 
  the 
  top 
  of 
  the 
  mountain 
  the 
  sedimentary 
  beds 
  

   have 
  totally 
  disappeared, 
  and 
  nothing 
  remains 
  but 
  the 
  trachyte, 
  with 
  

   its 
  splendent 
  brown 
  mica, 
  white 
  oligoclase, 
  and 
  long 
  needles 
  of 
  black 
  

   hornb.ende. 
  More 
  than 
  four 
  feet 
  ot 
  snow 
  covered 
  the 
  summit 
  at 
  the 
  

   time 
  of 
  our 
  ascent 
  (September 
  20, 
  1875) 
  and 
  it 
  was 
  more 
  difficult 
  than 
  

   it 
  otherwise 
  would 
  have 
  been 
  to 
  trace 
  the 
  exact 
  limits 
  of 
  the 
  capping 
  

   volcanic 
  rock. 
  Enough 
  was 
  seen, 
  however, 
  to 
  show 
  that 
  this 
  capping 
  

   rests 
  upon 
  one 
  of 
  the 
  changed 
  sandstone 
  strata, 
  which 
  at 
  that 
  elevation 
  

   has 
  a 
  slight 
  westerly 
  dip. 
  (Compare 
  section 
  iV.) 
  Diff'eiing 
  from 
  sta- 
  

   tion 
  121, 
  which 
  is 
  13,623 
  feet 
  above 
  sea-level, 
  is 
  the 
  lower 
  East 
  Spanish 
  

   Peak. 
  This 
  is 
  composed 
  entirely 
  of 
  trachytic 
  rock, 
  sending 
  out 
  also 
  

   a 
  number 
  of 
  radiating 
  dikes, 
  neither 
  so 
  many 
  nor 
  so 
  long, 
  however, 
  as 
  

   those 
  of 
  the 
  western 
  peak. 
  With 
  the 
  exphiuation 
  given 
  in 
  the 
  dis- 
  

   cussion 
  of 
  the 
  Carboniferous, 
  relative 
  to 
  the 
  upheaval 
  of 
  both 
  these 
  

   mountains 
  and 
  the 
  formation 
  of 
  a 
  fault, 
  this, 
  is 
  in 
  accordance. 
  It 
  is 
  evi- 
  

   dent 
  that 
  at 
  the 
  point 
  of 
  least 
  r:sistauce, 
  i. 
  e., 
  where 
  the 
  Carboniferous 
  

   strata 
  were 
  thinning 
  out, 
  the 
  quantity 
  of 
  volcanic 
  material 
  ejected 
  should 
  

   be 
  larger, 
  and 
  at 
  the 
  same 
  time 
  the 
  resisting 
  medium, 
  the 
  sandstones, 
  

   would 
  furnish 
  by 
  far 
  more 
  cracks 
  and 
  fissures 
  that 
  could 
  be 
  filled 
  by 
  the 
  

   injected 
  lavn. 
  Dr. 
  Hayden* 
  regards 
  these 
  peaks 
  as 
  a 
  " 
  gigantic 
  dike, 
  

   with 
  the 
  strike 
  about 
  northeast 
  and 
  southwest." 
  With 
  this 
  view 
  I 
  fully 
  

   agree, 
  adding 
  that 
  this 
  main 
  dike 
  has 
  clustered 
  around 
  it 
  a 
  veiy 
  large 
  

   number 
  of 
  accessories, 
  emanating 
  from 
  the 
  same 
  source 
  and 
  formed 
  syn- 
  

   chronously 
  with 
  the 
  elevation 
  of 
  the 
  peaks. 
  We 
  did 
  not 
  visit 
  the 
  base 
  

   of 
  East 
  Spanish, 
  but 
  I 
  have 
  no 
  doubt 
  that 
  metamorphosis 
  of 
  the 
  under- 
  

   lymg 
  strata 
  could 
  be 
  observed 
  here 
  similar 
  to 
  that 
  which 
  has 
  taken 
  place 
  

   on 
  aiid 
  near 
  station 
  121. 
  

  

  Near 
  the 
  edge 
  of 
  the 
  San 
  Luis 
  Valley, 
  south 
  of 
  station 
  115, 
  a 
  belt 
  of 
  

   trachyte 
  sets 
  in, 
  the 
  continuation 
  of 
  the 
  heavy 
  outflow 
  to 
  the 
  south. 
  

   Station 
  114 
  is 
  located 
  on 
  it 
  at 
  an 
  elevation 
  9,807 
  feet. 
  Low 
  rounded 
  

   hills 
  covered 
  with 
  piuon 
  and 
  juuii)er, 
  or 
  presenting 
  gentle 
  grassy 
  

   slopes, 
  characterize 
  the 
  region. 
  Deep 
  gullies 
  are 
  worn 
  into 
  the 
  vulcanic 
  

  

  * 
  Report 
  United 
  States 
  Geological 
  Survey 
  18(57 
  to 
  1669, 
  p. 
  153. 
  

   9 
  G 
  s 
  

  

  