﻿334 
  

  

  G. 
  ATTWOOD 
  02* 
  THE 
  GEOLOGY 
  

  

  Near 
  Paradise 
  Yalley 
  and 
  close 
  to 
  Orosi 
  the 
  country 
  rock 
  is 
  a 
  

   consolidated 
  ash, 
  in 
  which 
  augite-andesite 
  rocks 
  make 
  their 
  appear- 
  

   ance 
  through 
  the 
  crust. 
  Dark-coloured 
  boulders 
  are 
  also 
  found 
  in 
  

   the 
  river-beds 
  and 
  in 
  the 
  valleys. 
  The 
  augite-andesite 
  rock 
  (Ap- 
  

   pendix, 
  IS 
  T 
  o. 
  1, 
  p. 
  336) 
  presents 
  the 
  same 
  characteristics 
  as 
  those 
  

   found 
  near 
  San 
  Mateo 
  and 
  on 
  the 
  Aguacate 
  Mountains. 
  

  

  In 
  the 
  Yalley 
  of 
  Orosi 
  and 
  close 
  to 
  the 
  village 
  there 
  is 
  a 
  small 
  

   stream 
  called 
  Rio 
  Agua 
  Caliente 
  (hot-water 
  river) 
  ; 
  and 
  in 
  many 
  

   places 
  small 
  natural 
  springs 
  were 
  seen, 
  out 
  of 
  which 
  flowed 
  a 
  steady 
  

   stream 
  of 
  hot 
  water. 
  The 
  temperature 
  of 
  the 
  water 
  was 
  taken, 
  and 
  

   found 
  to 
  be 
  between 
  124 
  and 
  125 
  degrees 
  Fahr. 
  The 
  waters 
  are 
  

   sulphurous, 
  and 
  contain 
  a 
  considerable 
  amount 
  of 
  chloride 
  of 
  sodium, 
  

   with 
  soda 
  and 
  magnesia 
  carbonates, 
  iron 
  oxides, 
  &c. 
  ; 
  they 
  emitted 
  

   sulphuretted 
  hydrogen 
  and 
  carbonic 
  acid 
  gases, 
  but 
  not 
  to 
  a 
  great 
  

   extent. 
  The 
  springs 
  have 
  a 
  great 
  resemblance 
  to 
  the 
  hot 
  springs 
  

   found 
  to 
  the 
  north-west 
  of 
  the 
  city 
  of 
  Salt 
  Lake, 
  Utah, 
  situated 
  

   near 
  the 
  base 
  of 
  the 
  Wahsatch 
  range 
  of 
  mountains, 
  as 
  well 
  as 
  to 
  

   several 
  other 
  springs 
  in 
  the 
  neighbourhood. 
  

  

  About 
  12 
  miles 
  to 
  the 
  north-west 
  of 
  the 
  volcanoes 
  Irazu 
  and 
  

   Turrialba, 
  at 
  a 
  place 
  called 
  La 
  Palm 
  a, 
  some 
  rocks 
  were 
  collected. 
  

   Mr. 
  Hudleston's 
  description 
  of 
  them 
  (Appendix, 
  No. 
  2, 
  p. 
  337) 
  agrees 
  

   with 
  my 
  examination 
  ; 
  and 
  1 
  have 
  called 
  them 
  augite-andesites. 
  

  

  The 
  volcanoes 
  of 
  Irazu 
  and 
  Turrialba 
  present 
  many 
  features 
  of 
  

   great 
  interest. 
  Irazu 
  is 
  passive, 
  although 
  sulphur 
  vapours 
  are 
  now 
  

   and 
  then 
  noticeable. 
  It 
  has 
  been 
  quiet 
  since 
  1841; 
  and 
  immedi- 
  

   ately 
  after 
  its 
  becoming 
  so 
  a 
  fearful 
  earthquake 
  was 
  experienced, 
  

   which 
  nearly 
  destroyed 
  the 
  (then) 
  capital 
  of 
  the 
  Republic, 
  Cartago. 
  

   I 
  append 
  to 
  this 
  a 
  copy 
  of 
  a 
  photograph 
  (fig. 
  6), 
  showing 
  a 
  portion 
  

   of 
  the 
  crater, 
  and 
  giving 
  at 
  the 
  same 
  time 
  a 
  general 
  idea 
  of 
  the 
  gas- 
  

   vents 
  (blow-holes) 
  and 
  of 
  the 
  volcanic 
  ash 
  and 
  scoriae 
  found. 
  The 
  

   height 
  of 
  Irazu 
  has 
  been 
  variously 
  estimated. 
  Prof. 
  W. 
  M. 
  Gabb 
  

   places 
  it 
  at 
  11,356 
  feet 
  above 
  sea-level, 
  while 
  Prof, 
  von 
  Seebach, 
  

   Dr. 
  Don 
  Alejandro 
  von 
  Frantzius, 
  and 
  others 
  make 
  it 
  11,500 
  feet 
  

   above 
  sea-level*. 
  

  

  The 
  volcano 
  Turrialba 
  is 
  still 
  active 
  ; 
  but 
  its 
  activity 
  consists 
  

   chiefly 
  in 
  sending 
  out 
  clouds 
  of 
  vapour 
  with 
  a 
  little 
  ash. 
  During 
  

   my 
  visit 
  it 
  appeared 
  to 
  me 
  that 
  the 
  volcano 
  was 
  gradually 
  be- 
  

   coming 
  passive 
  and 
  was 
  following 
  the 
  example 
  of 
  Irazu. 
  I 
  ex- 
  

   perienced 
  numerous 
  but 
  at 
  the 
  same 
  time 
  slight 
  earthquake-shocks 
  

   at 
  San 
  Jose 
  and 
  some 
  other 
  places; 
  and 
  since 
  my 
  departure 
  from 
  

   the 
  country 
  very 
  heavy 
  shocks 
  have 
  taken 
  place. 
  Prom 
  what 
  

   observations 
  I 
  was 
  able 
  to 
  make, 
  it 
  appeared 
  most 
  likely 
  that 
  the 
  

   vents 
  of 
  the 
  crater 
  of 
  Turrialba 
  were 
  becoming 
  choked 
  up, 
  and 
  

   that 
  the 
  consequences 
  would 
  probably 
  be 
  either 
  a 
  fresh 
  and 
  violent 
  

   eruption 
  of 
  lava 
  or 
  severe 
  and 
  heavy 
  earthquakes. 
  

  

  * 
  Sf.e 
  W. 
  M. 
  Gabb, 
  " 
  Notes 
  en 
  Costa 
  Eica 
  Geology," 
  Amer. 
  Journ. 
  ser. 
  3, 
  

   vol. 
  ix. 
  p. 
  198, 
  &c. 
  ; 
  also 
  Lang, 
  " 
  Yuleanische 
  Ascbe 
  vom 
  Turrialba 
  (Costa 
  Eica)," 
  

   Nacbriebten 
  k. 
  Gesell. 
  Wissen. 
  und 
  Universitat 
  zu 
  Gottingen, 
  1875, 
  pp. 
  397- 
  

   411 
  ; 
  also 
  Seebacb, 
  a 
  paper 
  in 
  Petermann's 
  Mittbeilungen, 
  1865, 
  p. 
  321. 
  

  

  