﻿ENDLicH.] 
  SAN 
  JUAN 
  REGION 
  — 
  PAGOSA 
  SPRINGS. 
  185 
  

  

  egress 
  of 
  water 
  from 
  the 
  basin 
  and 
  to 
  the 
  fact 
  that 
  the 
  thermal 
  agents 
  

   upon 
  which 
  the 
  high 
  temperature 
  of 
  the 
  water 
  .depends 
  are 
  very 
  con- 
  

   stant 
  in 
  their 
  action. 
  

  

  An 
  analysis 
  of 
  the 
  main 
  spring 
  given 
  by 
  Dr. 
  Loew* 
  furnishes 
  the 
  fol- 
  

   lowing 
  result: 
  

  

  In 
  one 
  hundred 
  thousand 
  parts 
  of 
  water 
  are 
  contained 
  — 
  

  

  Socliutn 
  carbonate 
  , 
  4.70 
  

  

  Lithium 
  carbonate 
  - 
  0.71 
  

  

  Calcium 
  carbonate 
  59. 
  00 
  

  

  Magnesium 
  carbonate 
  4. 
  85 
  

  

  Potassium 
  sulphate 
  7. 
  13 
  

  

  Sodium 
  sulphate 
  - 
  221.66 
  

  

  Sodium 
  chloride 
  • 
  29.25 
  

  

  Silicic 
  acid 
  5.70 
  

  

  Organic 
  matter 
  Trace. 
  

  

  Total 
  solid 
  constituents 
  333.00 
  

  

  Analyses 
  of 
  three 
  of 
  the 
  smaller 
  springs 
  give 
  results 
  closely 
  agreeing 
  

   with 
  those 
  obtained 
  from 
  the 
  main 
  spring, 
  indicating 
  their 
  common 
  ori- 
  

   gin. 
  Professor 
  Stevenson 
  t 
  gives 
  an 
  elaborate 
  description 
  of 
  the 
  tu- 
  

   faceous 
  deposit, 
  and 
  the 
  minor 
  details 
  of 
  the 
  various 
  openings 
  and 
  

   "blow 
  holes" 
  that 
  are 
  scattered 
  throughout 
  the 
  former. 
  To 
  his 
  report 
  

   I 
  would 
  therefore 
  refer 
  for 
  information 
  regarding 
  such 
  features. 
  

  

  Pagosa 
  Springs 
  have 
  their 
  origin, 
  probably, 
  and 
  appear 
  at 
  the 
  surface 
  

   in 
  shales 
  of 
  the 
  Colorado 
  group. 
  In 
  the 
  same 
  shales, 
  about 
  a 
  mile 
  be- 
  

   low 
  Pagosa, 
  there 
  is 
  another 
  mineral 
  spring, 
  of 
  small 
  dimensions, 
  how- 
  

   ever. 
  It 
  is 
  located 
  at 
  the 
  base 
  of 
  a 
  bluff 
  and 
  sends 
  Its 
  water 
  directly 
  

   into 
  the 
  San 
  Juan. 
  It 
  is 
  a 
  fact 
  well 
  known 
  to 
  geologists 
  that 
  the 
  shales 
  

   of 
  the 
  Colorado 
  group 
  are 
  productive 
  of 
  many 
  mineral 
  springs, 
  but 
  it 
  is 
  

   exceedingly 
  difficult, 
  if 
  not 
  altogether 
  impossible, 
  to 
  explain 
  satisfacto- 
  

   rily 
  the 
  reason 
  why 
  the 
  water 
  should 
  have 
  so 
  high 
  a 
  temperature. 
  The 
  

   ancient 
  theory 
  of 
  reservoirs 
  extending 
  down 
  to 
  the 
  regions 
  of 
  perpetual 
  

   heat, 
  and 
  sending 
  their 
  waters 
  upward 
  for 
  miles 
  through 
  narrow 
  tubes 
  

   or 
  fissures, 
  has 
  long 
  since 
  failed 
  to 
  explain 
  the 
  origin 
  of 
  hot 
  springs. 
  It 
  

   seems 
  to 
  me 
  that 
  in 
  this 
  particular 
  instance 
  we 
  have 
  some 
  process 
  of 
  

   chemical 
  alteration 
  going 
  on 
  in 
  the 
  Colorado 
  shales 
  whereby 
  not 
  only 
  

   heat 
  is 
  produced, 
  but 
  the 
  mineral 
  constituents 
  of 
  the 
  shales 
  rendered 
  

   more 
  soluble 
  for 
  the 
  percolating 
  waters. 
  These 
  latter 
  becoming 
  heated 
  

   during 
  their 
  passage 
  through 
  the 
  portions 
  affected 
  by 
  a 
  process 
  of 
  

   chemical 
  metamorphosis, 
  find 
  their 
  way 
  to 
  the 
  surface, 
  as 
  any 
  other 
  

   springs 
  would, 
  at 
  the 
  nearest 
  point 
  offering 
  the 
  greatest 
  facilities 
  for 
  

   egress. 
  This 
  assumption, 
  *. 
  e., 
  that 
  hot 
  water 
  is 
  in 
  contact 
  with 
  the 
  

   products 
  of 
  chemical 
  decomposition, 
  would 
  account 
  for 
  the 
  large 
  per- 
  

   centage 
  of 
  mineral 
  constituents 
  in 
  solution, 
  even 
  though 
  the 
  passage 
  

   through 
  the 
  shales 
  should 
  be 
  but 
  limited 
  as 
  to 
  length. 
  It 
  is 
  always 
  a 
  

   matter 
  of 
  difficulty 
  to 
  explain 
  the 
  origin 
  of 
  heat 
  for 
  warm 
  springs, 
  and 
  

   the 
  above 
  view 
  is 
  presented 
  merely 
  as 
  the 
  most 
  probable 
  solution 
  of 
  

   the 
  question 
  in 
  this 
  particular 
  instance. 
  

  

  Near' 
  Pagoso 
  Springs 
  a 
  local 
  anticlinal 
  fold 
  was 
  observed 
  in 
  the 
  shales. 
  

   A 
  section, 
  (Section 
  X,) 
  taken 
  from 
  station 
  78, 
  looking 
  westward 
  will 
  ex- 
  

   plain 
  the 
  relative 
  positions 
  taken 
  by 
  the 
  shale, 
  the 
  superincumbent 
  Fox 
  

   Hills 
  strata, 
  and 
  the 
  volcanic 
  beds. 
  The 
  Colorado 
  shales 
  (a), 
  1,000 
  to 
  

   1,200 
  feet 
  in 
  thickness, 
  form 
  a 
  valley 
  along 
  one 
  of 
  the 
  small 
  tributaries 
  

  

  * 
  Ibid., 
  p. 
  627. 
  

  

  t 
  Report 
  on 
  Explorations 
  and 
  Surveys 
  West 
  of 
  One 
  Hundredth 
  Meridian, 
  1875, 
  vol. 
  

   iii, 
  p. 
  478. 
  

  

  