﻿262 
  

  

  inss 
  C. 
  A. 
  RAISES" 
  ON 
  S01EE 
  

  

  One 
  of 
  the 
  stronger 
  layers 
  proves, 
  on 
  microscopic 
  examination, 
  to 
  be 
  

   honeycombed 
  with 
  irregular 
  vesicles, 
  like 
  a 
  piece 
  of 
  trachyte. 
  The 
  

   firmness 
  of 
  the 
  band 
  is 
  due 
  to 
  the 
  hollows 
  being 
  filled 
  up 
  with 
  

   quartz 
  and 
  the 
  rock-mass 
  silicified. 
  This 
  layer 
  may 
  represent 
  the 
  

  

  ^ 
  

  

  I 
  5 
  

  

  I 
  

  

  •I 
  

  

  — 
  

   o 
  

  

  fcD 
  

  

  a 
  

  

  £ 
  s 
  

  

  ^ 
  «? 
  

  

  g 
  r 
  d 
  

  

  IS"* 
  

  

  m 
  

  

  g 
  go, 
  

  

  "_ 
  B 
  - 
  

  

  O 
  C 
  ^ 
  

   b 
  Ha 
  

  

  S 
  * 
  

  

  t£ 
  - 
  ft 
  

  

  <B 
  o 
  ?3 
  

  

  •5 
  G 
  72 
  

  

  -'3 
  » 
  

  

  J'S'S 
  

  

  *l 
  

  

  r 
  - 
  

  

  * 
  § 
  «, 
  

  

  cQ 
  g 
  

  

  Oft 
  

  

  g 
  5 
  oS 
  

  

  ft 
  C 
  ~ 
  

  

  03,3 
  & 
  

  

  outer 
  more 
  vesicular 
  part 
  of 
  the 
  original 
  lava-flow; 
  the 
  deeper 
  

   mass, 
  cooling 
  and 
  contracting, 
  gave 
  rise 
  to 
  perlitic 
  structures, 
  and 
  

   the 
  vapours 
  contained 
  may 
  have 
  been 
  emitted 
  and 
  collected 
  in 
  

   larger 
  vesicles, 
  which 
  occur 
  at 
  the 
  heart 
  of 
  agate-nodules. 
  

  

  