﻿EN-DLicH.] 
  SPANISH 
  PEAKS 
  DIKES. 
  135 
  

  

  their 
  walls 
  a 
  cast 
  of 
  the 
  strata, 
  opposite 
  which 
  each 
  particular 
  portion 
  

   of 
  the 
  dikes 
  became 
  rigid, 
  is 
  proof 
  of 
  the 
  fact 
  that 
  the 
  fissures 
  were 
  filled 
  

   by 
  either 
  liquid 
  or 
  plastic 
  material, 
  as 
  no 
  other 
  explanation 
  than 
  that 
  

   of 
  heat 
  can 
  be 
  accepted 
  for 
  the 
  formation 
  of 
  the 
  rocks 
  composing 
  the 
  

   dikes. 
  Either 
  the 
  fissures 
  were 
  filled 
  to 
  the 
  top, 
  i. 
  e. 
  to 
  surface 
  of 
  the 
  

   ground 
  or 
  stratum, 
  or 
  the 
  volcanic 
  material 
  passed 
  beyond 
  the 
  top 
  and 
  

   spread 
  itself 
  in 
  the 
  direction 
  that 
  afforded 
  the 
  most 
  ready 
  access, 
  of 
  

   which 
  latter 
  case 
  several 
  instances 
  have 
  been 
  mentioned 
  above. 
  

   Less 
  frequent 
  is 
  the 
  case 
  where 
  the 
  volcanic 
  material 
  did 
  not 
  reach 
  to 
  the 
  

   surface, 
  but 
  is 
  nowexposed 
  in 
  consequence 
  of 
  gradual 
  denudation 
  of 
  the 
  

   sedimentary 
  beds. 
  Gradual 
  erosion 
  and 
  decomposition, 
  though 
  at 
  the 
  

   same 
  time 
  attacking 
  the 
  dike-rock, 
  succeeded 
  in 
  wearing 
  away 
  more 
  

   rapidly 
  the 
  strata 
  adjoining 
  the 
  harder 
  and 
  more 
  resisting 
  trachyte 
  or 
  

   basalt. 
  Thus, 
  in 
  the 
  course 
  of 
  time, 
  the 
  strata 
  were 
  worn 
  away 
  for 
  the 
  

   vertical 
  distance 
  of 
  several 
  hundred 
  feet 
  sometimes, 
  while 
  the 
  rock, 
  

   formerly 
  inclosed 
  and 
  hidden, 
  gradually 
  rose 
  to 
  view. 
  Even 
  today 
  the 
  

   transportation 
  of 
  the 
  soil 
  is 
  going 
  on 
  at 
  a 
  more 
  rapid 
  ratio 
  than 
  the 
  

   crumbling 
  and 
  wearing 
  away 
  of 
  the 
  high 
  walls 
  that 
  have, 
  as 
  it 
  were, 
  

   grown 
  out 
  of 
  the 
  earth. 
  In 
  many 
  instances 
  the 
  erosion 
  of 
  surrounding 
  

   strata 
  was 
  so 
  complete 
  as 
  to 
  leave 
  thetrachytic 
  walls 
  standing 
  perfectly 
  

   free, 
  without 
  any 
  foreign 
  matter 
  whatever. 
  In 
  others, 
  however, 
  as 
  is 
  

   the 
  case 
  in 
  Stonewall 
  Valley, 
  the 
  baking 
  of 
  the 
  shale 
  strata 
  has 
  ren- 
  

   dered 
  them 
  sufficiently 
  hard 
  to 
  withstand 
  the 
  influence 
  of 
  atmospheric 
  

   and 
  other 
  agents 
  more 
  successfully, 
  and 
  we 
  have, 
  instead 
  of 
  a 
  well- 
  

   defined 
  wall, 
  one 
  flanked 
  on 
  either 
  side 
  by 
  a 
  sloping 
  mass 
  of 
  sediment- 
  

   ary 
  beds. 
  From 
  the 
  observations 
  made 
  it 
  can 
  only 
  seem 
  astonishing, 
  

   when 
  the 
  very 
  large 
  quantities 
  of 
  material 
  that 
  were 
  transported 
  from 
  

   their 
  place 
  of 
  deposition 
  is 
  considered. 
  It 
  is 
  true 
  that 
  many 
  rocks 
  will 
  

   be 
  rendered 
  by 
  far 
  more 
  liable 
  to 
  decomposition 
  and 
  disintegration 
  by 
  

   the 
  process 
  of 
  baking 
  or 
  ■ 
  metamorphosis, 
  but 
  either 
  very 
  powerful 
  

   agents 
  must 
  have 
  been 
  employed, 
  or 
  very 
  long 
  periods 
  of 
  time 
  required 
  

   to 
  remove, 
  gradatim, 
  300 
  to 
  400 
  feet 
  of 
  earth 
  or 
  rocks 
  from 
  so 
  considera- 
  

   ble 
  an 
  area. 
  

  

  In 
  looking 
  over 
  the 
  general 
  strike 
  of 
  the 
  dikes 
  in 
  this 
  district, 
  we 
  will 
  

   observe 
  that 
  there 
  is 
  not 
  sufficient 
  reason 
  for 
  assuming 
  a 
  preference 
  for 
  

   any 
  one 
  direction. 
  Had 
  the 
  forces 
  producing 
  the 
  disturbance 
  near 
  the 
  

   Spanish 
  Peaks 
  acted 
  uniformly 
  along 
  the 
  entire 
  eastern 
  border 
  of 
  the 
  

   Sangre 
  de 
  Cristo 
  Kange, 
  we 
  should 
  probably 
  have 
  occasion 
  to 
  observe 
  

   very 
  regular 
  and 
  similar 
  effects 
  throughout 
  the 
  region. 
  As 
  it 
  is, 
  how- 
  

   ever, 
  the 
  causes 
  for 
  the 
  formation 
  of 
  fissures 
  to 
  be 
  filled 
  are 
  localized, 
  

   and 
  the 
  effect 
  will 
  only 
  extend 
  itself 
  to 
  local 
  occurrences. 
  No 
  general- 
  

   izations, 
  therefore, 
  can 
  be 
  based 
  upon 
  the 
  existence 
  of 
  these 
  dikes, 
  save 
  

   the 
  one 
  that 
  they 
  were 
  formed 
  in 
  consequence 
  of 
  volcanic 
  seismic 
  ac- 
  

   tion. 
  In 
  the 
  landscape 
  they 
  have 
  a 
  decidedly 
  picturesque 
  effect, 
  produc- 
  

   ing 
  not 
  only 
  the 
  very 
  sharp 
  ridges 
  on 
  the 
  mountains 
  from 
  which 
  they 
  

   start, 
  and 
  the 
  hogbacks 
  when 
  not 
  entirely 
  denuded, 
  but 
  the 
  characteristic 
  

   walls 
  that 
  stretch 
  for 
  miles 
  across 
  a 
  sometimes 
  perfectly 
  level 
  country. 
  

   The 
  numerous 
  little 
  buttes, 
  remnants 
  or 
  portions 
  of 
  such 
  dikes, 
  afford 
  

   good 
  landmarks 
  in 
  the 
  lower 
  country, 
  and 
  are 
  welcome 
  as 
  stations 
  to 
  

   the 
  topograi'her 
  or 
  geologist. 
  Though 
  of 
  inconsiderable 
  elevation, 
  they 
  

   command 
  a 
  sufficiently 
  extensive 
  view 
  for 
  such 
  purposes. 
  A 
  number 
  of 
  

   them 
  occur 
  in 
  the 
  plains 
  east 
  of 
  the 
  Huerfano 
  region, 
  recognizable 
  from 
  

   a 
  distance 
  merely 
  as 
  small, 
  black, 
  stationary 
  objects. 
  

  

  Kegarding 
  the 
  age 
  of 
  the 
  Spanish 
  Peak 
  outflows 
  and 
  the 
  dike-system, 
  

   sufiBcieut 
  data 
  were 
  obtained 
  to 
  throw 
  light 
  upon 
  the 
  question. 
  As 
  

   mentioned 
  above, 
  most 
  of 
  the 
  dikes 
  traverse 
  Carboniferous 
  strata 
  on 
  the 
  

  

  