﻿300 
  MP. 
  T. 
  T. 
  GROOM 
  ON 
  A 
  TACHTLTTE 
  ASSOCIATED 
  WITH 
  THE 
  

  

  The 
  spherulites 
  are 
  generally 
  surrounded 
  by 
  a 
  clear, 
  sharply 
  denned, 
  

   isotropic 
  shell. 
  Some 
  of 
  these 
  granular 
  forms 
  closely 
  resemble 
  

   those 
  of 
  the 
  variolites 
  of 
  Durance. 
  In 
  the 
  occurrence 
  of 
  augite 
  in 
  

   • 
  a 
  spherulitic 
  form 
  the 
  Carrock 
  Fell 
  rock 
  approaches 
  the 
  diabase- 
  

   porphy 
  rites 
  and 
  variolites. 
  As 
  in 
  the 
  variolites, 
  the 
  sides 
  of 
  the 
  

   vein 
  and 
  the 
  porphyritic 
  crystals 
  have 
  formed 
  bases 
  of 
  aggregation 
  

   for 
  the 
  granules. 
  Owing 
  to 
  this 
  tendency, 
  which, 
  according 
  to 
  

   Rosenbusch, 
  is 
  commonly 
  met 
  with 
  in 
  tachylytes 
  and 
  augite-porphy- 
  

   rites, 
  the 
  central 
  part 
  of 
  the 
  vein 
  has 
  a 
  very 
  complicated 
  structure. 
  

   Minute 
  granular 
  pyroxenes 
  have 
  formed 
  accumulations 
  round 
  every 
  

   object 
  in 
  this 
  zone, 
  and 
  have 
  united 
  into 
  thick 
  anastomosing 
  bands, 
  

   forming 
  an 
  almost 
  isotropic 
  orange-coloured 
  meshwork. 
  

  

  At 
  the 
  very 
  margin 
  of 
  the 
  vein 
  the 
  glass 
  is 
  clear, 
  but 
  soon 
  becomes 
  

   opaque, 
  owing 
  to 
  the 
  appearance 
  of 
  vast 
  numbers 
  of 
  globidites, 
  

   cwnulites, 
  and 
  margarites, 
  probably 
  consisting 
  of 
  a 
  slightly 
  titaniferous 
  

   magnetite. 
  

  

  In 
  the 
  substance 
  of 
  the 
  pyroxene 
  meshwork 
  occur 
  a 
  number 
  of 
  

   small, 
  somewhat 
  irregular, 
  spherulitic 
  bodies. 
  These 
  consist 
  of 
  

   radially 
  arranged 
  fibres 
  having 
  all 
  the 
  appearance 
  of 
  felspar. 
  The 
  

   fibres 
  are 
  generally 
  accompanied 
  by 
  granules 
  of 
  augite 
  and 
  small 
  

   deposits 
  of 
  magnetite. 
  These 
  deposits 
  are 
  often 
  specially 
  developed 
  

   at 
  the 
  centre 
  of 
  the 
  pseudospJienilite, 
  where 
  they 
  commonly 
  form 
  a 
  

   dark 
  nucleus, 
  but 
  may 
  render 
  even 
  the 
  whole 
  spherulite 
  opaque. 
  

   The 
  cross 
  characteristic 
  of 
  true 
  spherulites 
  is 
  absent. 
  The 
  fibres 
  

   may 
  be 
  arranged 
  in 
  sheaves, 
  the 
  extinction-angle 
  of 
  which 
  is 
  nearly 
  

   parallel 
  to 
  their 
  length. 
  It 
  seems 
  probable, 
  from 
  the 
  optical 
  

   properties 
  of 
  these 
  spherulites, 
  as 
  well 
  as 
  from 
  the 
  analogy 
  of 
  the 
  

   varioles 
  of 
  the 
  Durance 
  variolites, 
  that 
  the 
  felspar 
  is 
  oligodase. 
  The 
  

   spherulites 
  have 
  frequently 
  formed 
  round 
  small 
  felspars 
  and 
  skeleton- 
  

   crystals, 
  and 
  like 
  them 
  are 
  generally 
  surrounded 
  by 
  a 
  deposit 
  of 
  

   magnetite. 
  Where 
  the 
  spherulites 
  are 
  particularly 
  crowded 
  together 
  

   their 
  individuality 
  may 
  be 
  lost, 
  and 
  the 
  whole 
  field 
  may 
  be 
  resolved 
  

   into 
  a 
  cryptocrystalline 
  aggregate 
  of 
  felspathic 
  fibres, 
  granules 
  of 
  

   augite 
  and 
  opacite 
  showing 
  a 
  complicated 
  arrangement. 
  

  

  The 
  latest 
  development 
  of 
  the 
  rock 
  appears 
  to 
  be 
  a 
  number 
  of 
  

   close 
  spherical 
  granules 
  of 
  quartz, 
  which 
  occur 
  in 
  the 
  clear 
  marginal 
  

   strip. 
  They 
  often 
  unite 
  into 
  groups 
  and 
  may 
  thus 
  form 
  imperfect 
  

   prisms 
  and 
  tabulae. 
  No 
  liquid 
  vesicles 
  are 
  present. 
  Their 
  late 
  

   origin 
  may 
  be 
  inferred 
  from 
  the 
  fact 
  that 
  they 
  occupy 
  cracks 
  

   traversing 
  all 
  the 
  zones 
  of 
  the 
  vein. 
  They 
  were 
  evidently 
  formed 
  

   after 
  the 
  consolidation 
  of 
  the 
  rock 
  had 
  proceeded 
  sufficiently 
  far 
  to 
  

   allow 
  of 
  the 
  formation 
  of 
  fissures 
  transverse 
  to 
  the 
  direction 
  of 
  flow. 
  

   The 
  cracks 
  have 
  two 
  directions, 
  one 
  series 
  perpendicular, 
  and 
  the 
  

   other 
  parallel 
  to 
  the 
  sides 
  of 
  the 
  vein 
  ; 
  they 
  are 
  apparently 
  due 
  

   to 
  the 
  shrinkage 
  consequent 
  on 
  cooling 
  of 
  the 
  vein. 
  

  

  Probable 
  Order 
  of 
  Consolidation. 
  

  

  The 
  first-formed 
  constituents 
  of 
  the 
  rock 
  were 
  the 
  porphyritic 
  

   crystals 
  of 
  the 
  augite, 
  basic 
  felspar, 
  vesicular 
  quartz, 
  and 
  magnetite 
  ; 
  

  

  