﻿576 
  DR. 
  W. 
  FRASER 
  HTJME 
  ON 
  [Dec. 
  1897, 
  

  

  deep 
  green 
  colour, 
  but 
  in 
  most 
  cases 
  are 
  altering 
  to 
  a 
  light 
  green 
  

   variety. 
  

  

  The 
  quartz-grains 
  are 
  usually 
  translucent, 
  the 
  largest 
  being 
  

   4-5 
  mm. 
  long 
  and 
  3 
  mm. 
  broad, 
  and 
  are 
  at 
  the 
  same 
  time 
  coloured 
  

   green 
  by 
  films 
  of 
  chlorite. 
  The 
  water-clear 
  examples 
  are 
  far 
  more 
  

   rounded 
  than 
  those 
  which 
  are 
  coloured, 
  but 
  some 
  still 
  retain 
  angular 
  

   outlines. 
  There 
  are 
  also 
  loose 
  aggregates 
  of 
  quartz 
  and 
  glauconite,. 
  

   probably 
  formed 
  in 
  situ. 
  We 
  may 
  thus 
  divide 
  the 
  coarser 
  detrital 
  

   materials 
  into 
  three 
  parts 
  : 
  — 
  

  

  (a) 
  Quartz 
  derived 
  from 
  schists, 
  etc., 
  usually 
  coloured 
  and 
  subangular. 
  

  

  (b) 
  Quartz-grains 
  which 
  are 
  water-clear, 
  transparent, 
  generally 
  highly 
  

   rounded, 
  and 
  probably 
  derived 
  from 
  clastic 
  rocks. 
  

  

  (<?) 
  Loose 
  friable 
  aggregates 
  of 
  quartz 
  and. 
  glauconite, 
  presumably 
  formed 
  in 
  

   place. 
  

  

  In 
  this 
  zone 
  first 
  appear 
  delicate 
  meshes 
  of 
  Hexactinellid 
  sponges 
  

   replaced 
  in 
  glauconite, 
  though 
  unfortunately 
  most 
  of 
  them 
  break 
  up 
  

   very 
  readily. 
  One 
  of 
  these, 
  which 
  was 
  somewhat 
  better 
  preserved 
  

   than 
  others, 
  has 
  been 
  examined 
  by 
  Dr. 
  G. 
  J. 
  Hinde, 
  who 
  informs 
  

   me 
  that 
  from 
  so 
  small 
  a 
  piece 
  it 
  is 
  impossible 
  to 
  state 
  the 
  genus 
  to 
  

   which 
  it 
  belonged, 
  though 
  it 
  may 
  not 
  improbably 
  be 
  a 
  mesh 
  of 
  

   Plocoscyphia. 
  

  

  The 
  finer 
  residue 
  is 
  composed 
  of 
  glauconite 
  and 
  angular 
  grains 
  

   of 
  quartz, 
  together 
  with 
  many 
  thin 
  flakes 
  of 
  silvery 
  white 
  mica. 
  

   The 
  glauconite 
  is 
  frequently 
  in 
  the 
  form 
  of 
  green 
  rods, 
  these 
  being 
  

   portions 
  of 
  the 
  spicular 
  meshes 
  previously 
  mentioned. 
  

  

  A 
  number 
  of 
  heavy 
  minerals 
  were 
  obtained 
  by 
  the 
  use 
  of 
  boro- 
  

   tungstate 
  of 
  cadmium 
  (sp. 
  gr. 
  2*93), 
  these 
  including 
  : 
  — 
  

  

  Zircon, 
  frequently 
  well 
  preserved, 
  showing 
  combinations 
  of 
  

   the 
  prism 
  and 
  pyramid 
  of 
  opposite 
  orders. 
  One 
  was 
  identical 
  in 
  

   form 
  with 
  Dana's 
  type 
  5 
  with 
  elongated 
  axis. 
  1 
  Beautifully 
  rounded 
  

   grains 
  are 
  also 
  numerous. 
  

  

  Rutile 
  in 
  deep 
  crimson 
  and 
  orange-yellow 
  fragments. 
  

  

  Tourmaline, 
  both 
  in 
  black 
  columnar 
  (schorl) 
  and 
  grey-brown 
  

   crystals. 
  

  

  Garnet 
  of 
  a 
  distinct 
  pink 
  colour, 
  in 
  perfectly 
  formed 
  rhombic 
  

   dodecahedra. 
  

  

  Kyanite, 
  showing 
  two 
  cleavages 
  at 
  90°, 
  low 
  polarization-colours, 
  

   and 
  extinction 
  at 
  about 
  30°. 
  

  

  Pyrites 
  is 
  present 
  as 
  small 
  spheres 
  of 
  brassy-metallic 
  lustre, 
  

   also 
  in 
  combinations 
  of 
  cubic 
  crystals, 
  while 
  rod-like 
  silvery 
  white 
  

   aggregates 
  must 
  probably 
  be 
  referred 
  to 
  marcasite. 
  A 
  Textularia 
  

   globulosa 
  was 
  observed 
  completely 
  replaced 
  in 
  pyrites. 
  

  

  Limoniteis 
  very 
  abundant 
  in 
  dull-red 
  amorphous 
  masses. 
  

  

  Muscovite 
  is 
  common 
  in 
  the 
  lighter 
  washings. 
  

  

  For 
  interprismatic 
  silicification 
  of 
  Inoceramus, 
  see 
  p. 
  556. 
  

  

  This 
  zone 
  markedly 
  differs 
  from 
  the 
  preceding 
  in 
  : 
  

  

  1. 
  The 
  great 
  increase 
  in 
  the 
  calcareous 
  constituents. 
  

  

  2. 
  The 
  presence 
  of 
  glauconitic 
  sponge-meshes. 
  

  

  1 
  ■ 
  System 
  of 
  Mineralogy,' 
  6th 
  ed. 
  (1892) 
  p. 
  483. 
  

  

  