﻿632 
  TACHYLYTE 
  FROM 
  TICTOEIA 
  PARE, 
  WHITEINUH, 
  NEAR 
  GLASGOW. 
  

  

  magnetite, 
  and 
  a 
  very 
  small 
  quantity 
  of 
  sparsely 
  distributed 
  un- 
  

   altered 
  ilmenite. 
  Finally, 
  there 
  is 
  more 
  or 
  less 
  interstitial 
  glassy 
  

   matter, 
  now 
  partially 
  devitrified. 
  The 
  phosphoric 
  acid 
  is, 
  no 
  doubt, 
  

   due 
  to 
  the 
  presence 
  of 
  apatite 
  ; 
  but 
  the 
  small 
  dimensions 
  of 
  such 
  

   crystals 
  would 
  easily 
  cause 
  them 
  to 
  be 
  overlooked 
  in 
  a 
  rock 
  of 
  such 
  

   finely 
  crystalline 
  texture. 
  

  

  Discussion. 
  

  

  The 
  Chairman 
  (Prof. 
  J. 
  W. 
  Judd), 
  with 
  reference 
  to 
  Mr. 
  Eutley's 
  

   suggestion 
  as 
  to 
  the 
  origin 
  of 
  the 
  two 
  layers 
  of 
  glassy 
  rock, 
  asked 
  for 
  

   further 
  information. 
  The 
  veins 
  were 
  ver}- 
  small, 
  and 
  it 
  was 
  admitted 
  

   that 
  it 
  was 
  difficult 
  to 
  suppose 
  they 
  had 
  produced 
  fusion 
  of 
  the 
  shale, 
  

   when 
  in 
  the 
  case 
  of 
  much 
  larger 
  ctykes 
  such 
  fusion 
  did 
  not 
  occur. 
  

  

  The 
  Author 
  stated 
  that 
  he 
  had 
  often 
  been 
  disappointed 
  in 
  his 
  

   search 
  for 
  cases 
  of 
  fusion 
  at 
  the 
  contacts 
  of 
  large 
  intrusive 
  veins 
  

   and 
  dykes, 
  while, 
  on 
  the 
  other 
  hand, 
  comparatively 
  small 
  veins 
  had 
  

   produced 
  alteration 
  of 
  the 
  adjacent 
  rocks. 
  He 
  considered 
  that 
  the 
  

   character 
  of 
  the 
  rock 
  must 
  be 
  taken 
  into 
  account. 
  Absolute 
  demon- 
  

   stration 
  of 
  the 
  fusion 
  of 
  the 
  shale 
  was 
  still 
  wanting 
  in 
  the 
  case 
  

   described, 
  but 
  he 
  believed 
  that 
  the 
  conclusions 
  given 
  in 
  the 
  paper 
  

   approximated 
  to 
  the 
  truth. 
  

  

  