﻿578 
  DR. 
  W. 
  FEASEE 
  HUME 
  ON 
  [DeC. 
  1 
  897, 
  

  

  The 
  principal 
  points 
  of 
  interest 
  in 
  this 
  zone 
  are 
  : 
  — 
  

  

  1. 
  The 
  predominance 
  of 
  calcareous 
  constituents. 
  

  

  2. 
  The 
  angularity 
  of 
  the 
  quartz-grains. 
  

  

  3. 
  The 
  abundance 
  and 
  good 
  preservation 
  of 
  glauconitic 
  casts 
  of 
  

  

  foraminifera 
  and 
  sponge-meshes. 
  

  

  4. 
  The 
  diminution 
  in 
  the 
  quantity 
  and 
  size 
  of 
  the 
  heavy 
  

  

  minerals, 
  with 
  the 
  exception 
  of 
  tourmaline. 
  

  

  White 
  Limestone. 
  (Zone 
  of 
  Belemnitella 
  mucronata.) 
  

   Woodburn 
  Glen. 
  (No. 
  1 
  b 
  in 
  Table 
  II.) 
  

  

  Of 
  this 
  white 
  chalk 
  82*4 
  grammes 
  was 
  dissolved 
  in 
  20 
  °/ 
  hydro- 
  

   chloric 
  acid, 
  yielding 
  -505 
  gramme 
  of 
  clay, 
  and 
  *015 
  gramme 
  of 
  heavy 
  

   residue. 
  

  

  Total 
  percentage 
  composition 
  : 
  — 
  

  

  Carbonate 
  of 
  lime 
  99-379% 
  

  

  Clay, 
  etc 
  *613 
  % 
  

  

  Heavy 
  residue 
  -0182% 
  

  

  100 
  

  

  The 
  heavy 
  residue 
  consists 
  of 
  a 
  few 
  small 
  angular 
  quartz 
  -grains, 
  

   two 
  or 
  three 
  flakes 
  of 
  muscovite, 
  and 
  limonite. 
  

  

  Same 
  Zone, 
  Divis 
  Hill. 
  (No. 
  1 
  in 
  Table 
  II.) 
  

  

  After 
  solution 
  as 
  above 
  81*42 
  grammes 
  yielded 
  -547 
  gramme 
  of 
  

   clayey 
  material, 
  and 
  *0042 
  gramme 
  of 
  heavy 
  residue, 
  the 
  latter 
  

   consisting 
  almost 
  entirely 
  of 
  limonite, 
  with 
  one 
  or 
  two 
  quartz-grains 
  

   (probably 
  wind-blown). 
  

  

  Total 
  percentage 
  composition 
  : 
  — 
  

  

  Carbonate 
  of 
  lime 
  99*323% 
  

  

  Clay, 
  etc 
  -672% 
  

  

  Heavy 
  residue 
  "005% 
  

  

  100 
  

  

  Same 
  Zone, 
  Magheramorne. 
  (No. 
  1 
  a 
  in 
  Table 
  II.) 
  

  

  On 
  analysis 
  80*6 
  grammes 
  yielded 
  *394 
  gramme 
  of 
  insoluble 
  clay, 
  

   silica, 
  etc., 
  and 
  *0327 
  gramme 
  of 
  heavy 
  residue, 
  giving 
  

  

  Carbonate 
  of 
  lime 
  99*47 
  °/ 
  

  

  Tine 
  residue 
  *488°/ 
  

  

  Heavy 
  residue 
  "041 
  % 
  

  

  100 
  

  

  The 
  main 
  residue 
  consists 
  of 
  a 
  thin, 
  flaky 
  brown 
  clay, 
  while 
  the 
  

   heavy 
  residue 
  is 
  in 
  greater 
  quantity 
  than 
  is 
  usual 
  with 
  chalks 
  from 
  

   the 
  Belemnitella 
  mucronata-zone. 
  This 
  excess 
  is 
  due, 
  in 
  some 
  degree, 
  

   to 
  the 
  presence 
  of 
  large 
  silicified 
  fragments 
  of 
  organisms 
  ; 
  but 
  the 
  

   alteration 
  has 
  proceeded 
  too 
  far 
  for 
  us 
  to 
  be 
  able 
  to 
  identify 
  the 
  

  

  