﻿EXDLICH.] 
  

  

  SPANISH 
  PEAKS-^DIKES. 
  133 
  

  

  point. 
  No 
  disturbance 
  could 
  be 
  observed 
  in 
  the 
  strata 
  that 
  were 
  

   traversed 
  by 
  the 
  volcanic 
  material, 
  a 
  feet 
  which 
  has 
  been 
  noticed 
  in 
  al- 
  

   most 
  every 
  instance, 
  and 
  shall 
  be 
  discussed 
  more 
  at 
  length 
  below, 
  wheu 
  

   speaking- 
  of 
  the 
  dikes 
  near 
  the 
  Spanish 
  Peaks. 
  Northeast 
  of 
  station 
  5 
  

   is 
  the 
  dome-shaped 
  mountain 
  that 
  has 
  been 
  alluded 
  to 
  above, 
  Muralla 
  

   Peak. 
  A 
  number 
  of 
  creeks 
  head 
  there, 
  belonging 
  to 
  the 
  Huerfano 
  

   drainage, 
  and 
  are 
  separated 
  from 
  each 
  other 
  by 
  narrow 
  ridges, 
  nearly 
  

   all 
  of 
  which 
  are 
  surmounted 
  by 
  one 
  of 
  the 
  wall-shaped 
  dikes. 
  The 
  latter 
  

   extend 
  into 
  the 
  valley, 
  at 
  the 
  base 
  of 
  the 
  mountain, 
  and 
  some 
  of 
  them 
  

   run 
  along 
  for 
  several 
  miles. 
  They 
  show 
  the 
  same 
  physical 
  characteris- 
  

   tics 
  as 
  nearly 
  all 
  the 
  others, 
  and 
  are 
  composed 
  of 
  porphyritic 
  trachyte. 
  

   More 
  than 
  ten 
  were 
  located, 
  issuing 
  radially 
  from 
  near 
  the 
  center 
  of 
  

   the 
  mountain. 
  Regarding 
  the 
  three 
  trachytic 
  outcrops, 
  upon 
  two 
  of 
  

   which 
  stations 
  4 
  and 
  5 
  (Veta 
  Peak) 
  are 
  located 
  as 
  one 
  huge 
  dike 
  in 
  

   connection, 
  probably, 
  so 
  far 
  as 
  regards 
  formation, 
  with 
  the 
  occurrence 
  

   of 
  the 
  fault 
  west 
  of 
  Spanish 
  Peaks, 
  we 
  find 
  it 
  to 
  be 
  14 
  miles 
  in 
  length, 
  

   striking 
  a 
  little 
  west 
  of 
  north. 
  Along 
  dike, 
  very 
  prominent 
  in 
  its 
  form 
  

   and 
  course, 
  occurs 
  between 
  the 
  Santa 
  Clara 
  and 
  Spanish 
  Creek, 
  north 
  

   of 
  station 
  lu9. 
  Its 
  course 
  is 
  about 
  northwest, 
  and 
  the 
  rock 
  composing 
  

   it 
  is 
  basalt. 
  Numerous 
  small 
  dikes 
  are 
  to 
  be 
  found 
  in 
  the 
  region 
  from 
  

   which 
  these 
  longer 
  ones 
  have 
  been 
  quoted, 
  but 
  they 
  are 
  obscured 
  partly 
  

   by 
  the 
  timber 
  ; 
  partly 
  they 
  have 
  crumbled 
  down 
  so 
  as 
  to 
  be 
  visible 
  no 
  

   longer 
  unless 
  upon 
  special 
  examination. 
  They 
  are 
  of 
  no 
  importance, 
  

   however, 
  in 
  considering 
  the 
  question 
  both 
  as 
  to 
  origin 
  and 
  cause 
  of 
  the 
  

   dikes. 
  

  

  Emaoatiag 
  from 
  and 
  in 
  the 
  vicinity 
  of 
  the 
  Spanish 
  Peaks 
  we 
  find 
  the 
  

   greatest 
  Duuiber 
  of 
  dikes 
  in 
  the 
  district. 
  More 
  may 
  be 
  observed 
  at 
  

   station 
  121 
  than 
  at 
  the 
  East 
  Spanish. 
  Radiating 
  in 
  every 
  direction 
  

   from 
  the 
  mono 
  tain, 
  with 
  its 
  summit 
  as 
  a 
  center, 
  these 
  dikes 
  stretch 
  for 
  

   several 
  miles 
  into 
  the 
  valley 
  of 
  the 
  Arapahoe. 
  It 
  is 
  they 
  that 
  have 
  

   caused 
  the 
  preservation 
  of 
  sedimentary 
  strata 
  in 
  the 
  shape 
  of 
  a 
  mount- 
  

   ain. 
  Some 
  of 
  them 
  show 
  a 
  remarkably 
  straight 
  course, 
  others 
  more 
  

   wavering 
  lines. 
  A 
  small 
  map 
  has 
  been 
  prepared 
  showing 
  their 
  dis- 
  

   tribution, 
  and 
  to 
  this 
  I 
  would 
  refer. 
  In 
  consequence 
  of 
  the 
  radiation, 
  

   no 
  prevciiling 
  direction 
  can 
  be 
  assigned 
  to 
  the 
  courses 
  of 
  the 
  dikes 
  ; 
  but 
  

   it 
  may 
  be 
  observed 
  that 
  the 
  longest 
  ones 
  are 
  at 
  right 
  angles 
  to 
  the 
  

   strike 
  of 
  the 
  two 
  mountains 
  themselves, 
  while 
  the 
  others, 
  though 
  of 
  

   consideriib^e 
  length, 
  do 
  not 
  show 
  that 
  regularity 
  either 
  in 
  course 
  or 
  

   form. 
  This 
  agrees 
  with 
  the 
  theory 
  explaining 
  the 
  position 
  of 
  the 
  sand- 
  

   stones 
  in 
  the 
  mountain.' 
  In 
  case 
  of 
  any 
  disturbance, 
  such 
  as 
  has 
  been 
  

   assumed, 
  the 
  greatest 
  strain 
  would 
  fall 
  in 
  such 
  a 
  way 
  as 
  to 
  i)roduce 
  a 
  

   breaking 
  of 
  the 
  strata 
  at 
  right 
  angles 
  to 
  their 
  dip, 
  and 
  it 
  is 
  at 
  right 
  

   angles 
  to 
  this 
  dip 
  that 
  we 
  find 
  the 
  longest 
  and 
  most 
  regular 
  dikes. 
  

   Some 
  of 
  them 
  present 
  an 
  appearance 
  that 
  cannot 
  but 
  be 
  compared 
  to 
  a 
  

   wall, 
  particularly 
  so 
  Huerfano 
  dike, 
  which 
  is 
  about 
  8 
  miles 
  in 
  length. 
  

   Spanish 
  dike 
  is 
  the 
  longest 
  one, 
  measuring 
  nearly 
  10 
  miles. 
  Both 
  are 
  

   several 
  hundred 
  feet 
  high 
  and 
  stand 
  perfectly 
  vertical. 
  Transverse 
  

   dikes 
  also 
  exist, 
  crossing 
  the 
  others 
  at 
  acute 
  angles. 
  Ramifications 
  take 
  

   ])lace 
  in 
  several 
  instances, 
  the 
  branches 
  retaining 
  the 
  same 
  size, 
  how- 
  

   ever, 
  that 
  is 
  shown 
  by 
  the 
  one 
  from 
  which 
  they 
  started. 
  Wherever 
  

   creeks 
  were 
  to 
  be 
  crossed 
  by 
  them, 
  they 
  are 
  broken 
  through, 
  and 
  in 
  no 
  

   instance 
  have 
  they 
  caused 
  any 
  serious 
  deflection 
  of 
  the 
  water-courses. 
  

   SM)all, 
  local 
  bends, 
  of 
  course, 
  have 
  been 
  produced, 
  but 
  no 
  entire^ 
  

   alteration 
  of 
  the 
  general 
  direction. 
  Altogether 
  more 
  than 
  fifty 
  of 
  

   these 
  dikes 
  have 
  been 
  located 
  near 
  Spanish 
  Peaks, 
  but 
  there 
  are 
  

   manv 
  more 
  that 
  were 
  either 
  hidden 
  or 
  too 
  small 
  to 
  be 
  noticed. 
  Imme- 
  

  

  