﻿OF 
  A 
  PAET 
  OF 
  COSTA 
  RICA. 
  

  

  335 
  

  

  Pig. 
  6. 
  — 
  View 
  of 
  a 
  Part 
  of 
  the 
  Crater 
  of 
  the 
  Volcano 
  Irazu, 
  showing 
  

   Volcanic 
  ash, 
  Scoriae, 
  &fc, 
  and 
  Gas-vents. 
  Prom 
  a 
  photograph 
  

   taken 
  in 
  the 
  direction 
  of 
  the 
  Atlantic. 
  

  

  Turrialba 
  is 
  abont 
  11,500 
  feet 
  above 
  sea-level. 
  Many 
  differences 
  

   of 
  opinion 
  have 
  existed 
  in 
  regard 
  to 
  its 
  height 
  ; 
  but 
  the 
  maximum 
  

   difference 
  is 
  only 
  ] 
  50 
  feet. 
  Prom 
  my 
  observations 
  Tunialba 
  is 
  about 
  

   from 
  60 
  to 
  100 
  feet 
  higher 
  than 
  Irazu. 
  

  

  Conclusions. 
  

  

  The 
  conclusions 
  at 
  which 
  I 
  have 
  arrived 
  from 
  a 
  personal 
  survey 
  and 
  

   examination 
  of 
  the 
  country 
  which 
  I 
  have 
  just 
  described, 
  and 
  also 
  

   from 
  the 
  analyses 
  and 
  microscopical 
  examinations 
  made 
  by 
  Mr. 
  "W. 
  

   H. 
  Hudleston 
  and 
  myself 
  are 
  as 
  follows 
  : 
  — 
  

  

  1st. 
  The 
  country 
  rock, 
  or 
  the 
  general 
  representative 
  rock 
  of 
  the 
  

   country, 
  is 
  a 
  consolidated 
  volcanic 
  ash 
  associated 
  with 
  augite- 
  

   andesite. 
  

  

  2nd. 
  The 
  filling 
  of 
  the 
  fissures, 
  now 
  mineral 
  lodes, 
  in 
  the 
  Agua- 
  

   cate 
  Mountains 
  took 
  place 
  in 
  the 
  Tertiary 
  age, 
  and 
  most 
  probably 
  

   in 
  the 
  Pliocene. 
  

  

  3rd. 
  The 
  augite-andesites 
  of 
  the 
  Aguacate 
  Mountains 
  are 
  pro- 
  

   bably 
  contemporaneous 
  with, 
  and 
  have 
  thus 
  contributed 
  largely 
  to 
  

   the 
  mineral 
  deposition 
  and 
  formation 
  of 
  the 
  metalliferous 
  lodes. 
  

  

  