﻿OP 
  A 
  PART 
  OP 
  COSTA 
  EICA. 
  

  

  329 
  

  

  the 
  peninsula 
  of 
  Punta 
  Arenas, 
  owing 
  to 
  the 
  strong 
  south-west 
  cur- 
  

   rent 
  in 
  the 
  Bay 
  of 
  Nicoya 
  bringing 
  all 
  the 
  sands 
  from 
  the 
  rivers 
  

   Rio 
  Grande, 
  Jesus 
  Maria, 
  and 
  Rio 
  Barranca, 
  all 
  of 
  which 
  rivers 
  

   bring 
  down 
  with 
  them 
  the 
  decomposed 
  igneous 
  rocks 
  from 
  the 
  

   Costa-Rican 
  Andes 
  and 
  its 
  spurs. 
  However, 
  the 
  peninsula 
  is 
  being 
  

   cut 
  away 
  in 
  the 
  south 
  by 
  the 
  current, 
  as 
  is 
  proved 
  by 
  the 
  trees 
  

   lately 
  overturned. 
  

  

  Fig. 
  2. 
  — 
  Sketch 
  Plan 
  of 
  the 
  Peninsula 
  of 
  Punta 
  Arenas. 
  

  

  a. 
  Fine 
  Sand. 
  

  

  b. 
  Consolidated 
  Volcanic 
  Ash. 
  

  

  On 
  crossing 
  the 
  Rio 
  Barranca, 
  and 
  proceeding 
  as 
  far 
  as 
  the 
  vol- 
  

   canoes 
  of 
  Irazu 
  and 
  Turrialba 
  (see 
  Map, 
  PI. 
  XII.), 
  and 
  then 
  on 
  

   to 
  the 
  old 
  Indian 
  settlement 
  called 
  Orosi, 
  the 
  rocks 
  met 
  with 
  present 
  

   a 
  great 
  similarity 
  in 
  their 
  structure. 
  The 
  general 
  rock 
  of 
  the 
  

   district 
  shows 
  itself 
  on 
  both 
  sides 
  of 
  the 
  Rio 
  Barranca 
  after 
  leaving 
  

   the 
  sands 
  of 
  the 
  Punta- 
  Arenas 
  peninsula, 
  and 
  continues 
  for 
  about 
  

   fifty 
  miles 
  in 
  an 
  easterly 
  direction 
  towards 
  Cartago, 
  the 
  ancient 
  

   capital 
  of 
  the 
  country, 
  although 
  on 
  the 
  Aguacate 
  range 
  of 
  mountains 
  

   rocks 
  of 
  volcanic 
  origin 
  make 
  their 
  appearance. 
  The 
  same 
  general 
  

   rock 
  is 
  also 
  found 
  beyond 
  Cartago, 
  in 
  the 
  direction 
  of 
  Orosi. 
  The 
  

   rock 
  is 
  fine-grained, 
  presenting 
  a 
  greenish 
  appearance 
  ; 
  and 
  wherever 
  

   it 
  is 
  not 
  weathered 
  it 
  is 
  tough 
  and 
  difficult 
  to 
  quarry. 
  It 
  has 
  a 
  

   granular 
  base, 
  and 
  contains 
  crystals 
  of 
  triclinic 
  felspar 
  with 
  augite, 
  

   also 
  small 
  quantities 
  of 
  magnetite 
  ; 
  specimens 
  obtained 
  on 
  the 
  moun- 
  

   tain-range 
  of 
  Aguacate, 
  near 
  the 
  gold- 
  and 
  silver 
  -mines, 
  show 
  specks 
  

   of 
  pyrites, 
  and 
  may 
  be 
  regarded 
  as 
  a 
  consolidated 
  volcanic 
  ash. 
  

  

  The 
  specimen 
  collected 
  near 
  the 
  Rio 
  Barranca 
  was 
  more 
  coarsely 
  

   fragmental 
  than 
  those 
  collected 
  in 
  the 
  mountains 
  further 
  in 
  the 
  

   interior, 
  and 
  the 
  felspars 
  Avere 
  more 
  weathered 
  (Appendix, 
  No. 
  8, 
  

   p. 
  339). 
  

  

  On 
  the 
  south-east 
  side 
  of 
  the 
  Rio 
  Barranca, 
  before 
  the 
  village 
  of 
  

   Esparto 
  is 
  reached, 
  large 
  boulders 
  of 
  a 
  black 
  rock 
  are 
  frequently 
  

   seen. 
  They 
  were 
  examined, 
  but 
  were 
  evidently 
  strangers 
  to 
  this 
  

   particular 
  locality. 
  From 
  Esparto 
  to 
  San 
  Mateo 
  the 
  country 
  is 
  

   rugged 
  and 
  mountainous, 
  the 
  surface 
  being 
  cut 
  up 
  by 
  a 
  continuous 
  

  

  