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  MISS 
  C. 
  A. 
  RAISIN 
  OS 
  SOME 
  

  

  crust 
  ; 
  but 
  this 
  is 
  thin 
  compared 
  with 
  the 
  quartz-tilled 
  interior, 
  and 
  

   may 
  represent 
  the 
  early 
  development 
  rather 
  than 
  the 
  vanishing 
  

   traces 
  of 
  large 
  spherulites 
  (fig. 
  9). 
  Crystals 
  of 
  felspar 
  occur 
  close 
  

  

  Fig. 
  9. 
  — 
  One 
  half 
  of 
  a 
  Siliceous 
  Amygdaloid, 
  with 
  a 
  narrow 
  sjfheru- 
  

   litic 
  border. 
  From 
  old 
  lava-flow 
  at 
  south-east 
  of 
  Pen-y-chain. 
  

   (Enlarged 
  8 
  diameters.) 
  

  

  This 
  specimen 
  is 
  from 
  a 
  rock 
  which 
  contains 
  the 
  amygdaloids 
  of 
  fig. 
  8. 
  

  

  to 
  the 
  nodules, 
  being 
  actually 
  sometimes 
  in 
  contact 
  with 
  them 
  ; 
  some 
  

   are 
  kaolinized, 
  others 
  exhibit 
  plagioclase 
  twinning, 
  but 
  in 
  none 
  is 
  

   there 
  a 
  replacement 
  by 
  quartz-granules. 
  The 
  nodules 
  are 
  elongated, 
  

   and 
  in 
  more 
  than 
  one 
  instance 
  they 
  bend 
  around 
  the 
  angle 
  of 
  a 
  

   porphyritic 
  crystal, 
  at 
  a 
  little 
  distance 
  from 
  it, 
  just 
  as 
  would 
  often 
  

   occur 
  in 
  the 
  formation 
  of 
  a 
  vesicle. 
  Thus 
  they 
  seem 
  to 
  be 
  amyg- 
  

   daloidal, 
  and 
  in 
  that 
  case 
  we 
  should 
  be 
  justified 
  in 
  concluding 
  that 
  

   similar 
  cavities 
  once 
  existed 
  in 
  the 
  neighbouring 
  beds, 
  around 
  which 
  

   a 
  spherulitic 
  growth 
  arose; 
  according 
  to 
  Lagorio 
  it 
  would 
  be 
  especially 
  

   induced 
  where 
  gases 
  and 
  vapours 
  passed 
  through 
  the 
  rock*. 
  

  

  The 
  above 
  interpretation 
  seems 
  corroborated 
  by 
  some 
  small 
  

   pyromerides 
  from 
  Jersey, 
  in 
  which 
  the 
  interior 
  has 
  all 
  the 
  appearance 
  

   of 
  similar 
  oval-shaped 
  amygdaloids. 
  A 
  slide 
  cut 
  from 
  another 
  rock 
  

   at 
  Boulay 
  Bay 
  exhibits 
  a 
  contorted 
  fluidal 
  structure, 
  with 
  appar- 
  

   ently 
  rounded 
  quartz-filled 
  vesicles, 
  as 
  if 
  the 
  rock 
  was 
  originally 
  

   glassy 
  and 
  pumiceous. 
  Small 
  veinlets 
  of 
  fibrous 
  chalcedony 
  extend 
  

   between 
  the 
  lines 
  of 
  flow 
  or 
  curve 
  around 
  the 
  vesicles. 
  An 
  attempt 
  

   at 
  spherulitic 
  growth 
  seems 
  to 
  fringe 
  the 
  vesicles, 
  the 
  chalcedonic 
  

   veins, 
  and 
  the 
  surfaces 
  of 
  contorted 
  fluidal 
  masses. 
  It 
  had 
  been 
  

   suggested 
  by 
  Professor 
  Bonney, 
  from 
  his 
  observations 
  in 
  the 
  field, 
  

   that 
  some 
  pyromerides 
  might 
  possibly 
  be 
  connected 
  in 
  their 
  develop- 
  

   ment 
  with 
  a 
  differentiation 
  of 
  material 
  in 
  the 
  lava, 
  such 
  as 
  gives 
  

   rise 
  to 
  a 
  fluidal 
  structure. 
  

  

  We 
  might 
  compare 
  with 
  nodules 
  produced 
  as 
  I 
  have 
  just 
  sug- 
  

  

  * 
  Min. 
  Mittheil. 
  Bd. 
  viii. 
  p. 
  421. 
  Abstract 
  in 
  Min. 
  Mag. 
  1887, 
  vol. 
  vii. 
  

   p, 
  223. 
  

  

  