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  MISS 
  C. 
  A. 
  RAISIN 
  ON 
  SOME 
  

  

  5 
  inches 
  or 
  more 
  in 
  diameter, 
  are 
  scattered 
  through 
  the 
  rock. 
  

   The 
  chalcedony, 
  which 
  fills 
  the 
  interior, 
  often 
  shows 
  a 
  platy 
  struc- 
  

   ture 
  parallel 
  to 
  the 
  rock-lamination. 
  The 
  nodules 
  are 
  rounded, 
  but 
  

   are 
  furnished 
  with 
  curious 
  protuberant 
  ridges, 
  generally 
  a 
  complete 
  

   equatorial 
  and 
  a 
  partial 
  meridional 
  one, 
  and 
  occasionally 
  others, 
  

   which 
  unite 
  with 
  some 
  of 
  the 
  larger. 
  The 
  ridges 
  are 
  sometimes 
  rather 
  

  

  Fig. 
  5. 
  — 
  Longitudinal 
  Section 
  of 
  Nodule 
  from 
  east 
  of 
  Careg-y-defaid. 
  

  

  (Nat. 
  size.) 
  

  

  It 
  contains 
  three 
  chambers 
  filled 
  with 
  chalcedony 
  (a). 
  The 
  crust 
  is 
  spherulitic, 
  

   with 
  porphyritic 
  felspars, 
  of 
  which 
  two 
  are 
  apparently 
  clear 
  arid 
  silicified, 
  

   the 
  others 
  nearly 
  opaque. 
  

  

  wavy. 
  I 
  thought 
  I 
  could 
  trace 
  them 
  in 
  one 
  or 
  two 
  cases 
  to 
  the 
  

   continuation 
  of 
  bedding- 
  or 
  joint-planes, 
  and 
  the 
  internal 
  cavity 
  

   often 
  extends 
  to 
  them. 
  The 
  most 
  regular 
  of 
  the 
  nodules 
  reminded 
  

   me, 
  in 
  external 
  form, 
  of 
  that 
  which 
  von 
  Eichthofen 
  figures 
  as 
  the 
  

   usual 
  type 
  of 
  lithophysse 
  *, 
  only 
  without 
  the 
  internal 
  lamellae. 
  

   The 
  radialized 
  crust, 
  here 
  as 
  elsewhere, 
  is 
  influenced 
  by 
  the 
  in- 
  

   ternal 
  cavity, 
  and 
  follows 
  the 
  stellar 
  points 
  of 
  the 
  interior, 
  so 
  as 
  

   to 
  form 
  the 
  outer 
  skin 
  of 
  the 
  ridges 
  (fig. 
  6). 
  The 
  interior 
  has 
  

   the 
  appearance 
  of 
  a 
  possible 
  vesicle, 
  irregular 
  in 
  shape, 
  often 
  with 
  

   convex 
  sides 
  and 
  projecting 
  angles. 
  Where 
  a 
  cavity 
  can 
  be 
  distin- 
  

   guisned 
  within 
  the 
  pyromerides 
  of 
  Jersey, 
  it 
  may 
  be 
  similar 
  in 
  form, 
  

   and 
  is 
  often 
  filled 
  with 
  chalcedony. 
  At 
  one 
  part 
  of 
  the 
  Pen-y-chain 
  

   nodule, 
  between 
  the 
  siliceous 
  interior 
  and 
  the 
  spherulitic 
  crust, 
  a 
  

   small 
  mass 
  intervenes, 
  consisting 
  of 
  minute 
  scale-like 
  globulites, 
  

   scattered 
  through 
  shadowy 
  chalcedonic 
  granules. 
  If 
  this 
  is 
  due 
  to 
  

   the 
  alteration 
  of 
  part 
  of 
  the 
  rock-mass, 
  as 
  seems 
  probable, 
  it 
  would 
  

   negative 
  here 
  the 
  theory 
  of 
  an 
  originally 
  complete 
  spherulite. 
  The 
  

   radial 
  fibres 
  seem 
  posterior 
  to 
  certain 
  largish 
  spherulites 
  within 
  the 
  

   crust, 
  which 
  also 
  contains 
  others, 
  much 
  smaller 
  and 
  rudimentary, 
  

  

  * 
  Jahrb. 
  der 
  k. 
  k. 
  geol. 
  Eeichs. 
  1860, 
  p. 
  181. 
  

  

  