﻿VICTORIA 
  PARK, 
  WHITEINCH, 
  NEAR 
  GLASGOW. 
  629 
  

  

  tionably 
  belongs 
  to 
  the 
  whin-vein, 
  indicates 
  that 
  there 
  is 
  a 
  difference 
  

   in 
  the 
  chemical 
  composition 
  of 
  the 
  two 
  bands, 
  the 
  deep 
  colour 
  of 
  the 
  

   glass 
  in 
  contact 
  with 
  the 
  shale 
  being 
  probably 
  due 
  to 
  the 
  presence 
  of 
  

   metallic 
  oxides 
  in 
  the 
  latter 
  rock. 
  If 
  this 
  be 
  so, 
  the 
  dark-colonred 
  

   glass 
  results 
  from 
  the 
  fusion 
  of 
  the 
  shale. 
  It 
  may 
  be 
  that 
  this 
  

   is 
  merely 
  the 
  outermost 
  glassy 
  selvage 
  of 
  the 
  whin 
  -vein, 
  tinted 
  

   more 
  or 
  less 
  by 
  metallic 
  oxides 
  derived 
  from 
  a 
  very 
  slight 
  in- 
  

   cipient 
  fusion 
  of 
  the 
  shale. 
  Assuming, 
  for 
  the 
  moment, 
  that 
  this 
  

   is 
  the 
  case, 
  we 
  have 
  to 
  account 
  for 
  the 
  well-defined 
  sinuous 
  line 
  of 
  

   demarcation 
  between 
  the 
  coloured 
  and 
  colourless 
  bands 
  of 
  glass, 
  and 
  

   regarding 
  these 
  two 
  bands 
  as 
  viscous 
  matter 
  of 
  different 
  densities, 
  

   the 
  existence 
  of 
  such 
  a 
  line, 
  the 
  trace 
  of 
  an 
  undulating 
  separation- 
  

   surface, 
  in 
  a 
  rapidly 
  cooling 
  magma 
  is 
  precisely 
  what 
  one 
  would 
  

   expect. 
  A 
  more 
  perfect 
  incorporation 
  of 
  the 
  two 
  glasses 
  would 
  have 
  

   resulted 
  in 
  a 
  lowering 
  of 
  tint 
  and 
  in 
  the 
  abolition 
  of 
  any 
  such 
  line 
  

   of 
  demarcation. 
  The 
  colourless 
  glass 
  may 
  therefore 
  be 
  regarded 
  

   as 
  the 
  tachylyte 
  of 
  the 
  whin- 
  vein, 
  while 
  the 
  darker 
  band 
  I 
  propose 
  

   to 
  distinguish 
  by 
  the 
  term 
  shale-glass. 
  

  

  As 
  already 
  pointed 
  out 
  by 
  Messrs. 
  J. 
  Young 
  and 
  D. 
  Corse 
  Glen, 
  

   a 
  considerable 
  variation 
  in 
  texture 
  and 
  colour 
  is 
  met 
  with 
  in 
  the 
  

   material 
  constituting 
  the 
  intrusive 
  veins 
  at 
  Whiteinch, 
  and, 
  to 
  quote 
  

   their 
  own 
  words, 
  " 
  Where 
  thinner 
  sheets 
  and 
  veins 
  derived 
  from 
  the 
  

   main 
  mass 
  are 
  found 
  to 
  be 
  intrusive 
  in 
  higher 
  or 
  lower 
  levels 
  of 
  the 
  

   strata 
  in 
  the 
  same 
  locality, 
  as 
  in 
  the 
  quarry 
  at 
  Victoria 
  Park, 
  the 
  

   rock 
  is 
  generally 
  seen 
  to 
  pass 
  from 
  its 
  normal 
  dark 
  colour 
  into 
  

   different 
  shades 
  of 
  light 
  grey 
  and 
  greyish 
  white, 
  the 
  alteration 
  being 
  

   evidently 
  due 
  to 
  its 
  contact 
  with 
  the 
  sedimentary 
  rock 
  and 
  to 
  rapid 
  

   cooling, 
  especially 
  along 
  the 
  lines 
  of 
  contact 
  " 
  *. 
  

  

  Mr. 
  Young 
  has 
  kindly 
  forwarded 
  small 
  specimens 
  of 
  the 
  veins 
  at 
  

   Victoria 
  Park, 
  showing 
  these 
  variations, 
  and 
  I 
  have 
  examined 
  

   sections 
  made 
  from 
  those 
  which 
  appeared 
  most 
  typical, 
  with 
  the 
  

   result 
  that 
  I 
  find 
  the 
  dark, 
  coarsely 
  crystalline 
  dolerite 
  to 
  consist 
  of 
  

   felspars 
  which, 
  from 
  their 
  extinction 
  -angles, 
  appear 
  to 
  be 
  labradorite, 
  

   but 
  which 
  are, 
  for 
  the 
  most 
  part, 
  in 
  too 
  advanced 
  a 
  stage 
  of 
  

   alteration 
  to 
  admit 
  of 
  any 
  optical 
  determination. 
  Olivine 
  and 
  

   ilmenite 
  are 
  also 
  plentiful 
  — 
  the 
  former 
  mineral 
  often 
  showing 
  

   alteration 
  into 
  serpentine 
  or 
  calcite, 
  while 
  the 
  ilmenite 
  has 
  been, 
  in 
  

   great 
  part, 
  converted 
  into 
  leucoxene. 
  Apatite 
  is 
  also 
  plentiful 
  in 
  

   the 
  form 
  of 
  slender 
  hexagonal 
  prisms. 
  A 
  considerable 
  amount 
  of 
  

   green 
  to 
  brownish-green 
  chlorite 
  is 
  also 
  present, 
  occasionally 
  form- 
  

   ing 
  fringes, 
  composed 
  of 
  fan-shaped 
  aggregates 
  of 
  plates, 
  around 
  the 
  

   walls 
  of 
  vesicles, 
  the 
  central 
  portion 
  of 
  the 
  vesicle 
  being 
  frequently 
  

   filled 
  with 
  calcite. 
  In 
  addition 
  to 
  the 
  minerals 
  mentioned, 
  the 
  

   section 
  shows 
  a 
  few 
  small 
  crystals 
  of 
  a 
  dark-brown 
  magnesian 
  mica, 
  

   and 
  here 
  and 
  there 
  a 
  speck 
  of 
  pyrites. 
  

  

  Another 
  specimen 
  from 
  the 
  same 
  locality, 
  but 
  of 
  a 
  totally 
  different 
  

   character 
  from 
  the 
  preceding, 
  is 
  very 
  fine-grained 
  in 
  texture, 
  and 
  of 
  

   a 
  pale 
  bluish-grey, 
  passing 
  into 
  a 
  buff 
  colour. 
  In 
  a 
  section 
  taken 
  

  

  * 
  Trans. 
  Geol. 
  Soc. 
  Glasgow, 
  1888. 
  

  

  