﻿Archcean 
  Hocks 
  from 
  the 
  Mysore 
  State. 
  211 
  

  

  very 
  definite 
  conclusions. 
  It 
  may 
  be 
  noted 
  that 
  the 
  

   members 
  o£ 
  the 
  Champion 
  gneiss 
  series 
  show 
  least 
  variation, 
  

   those 
  of 
  the 
  Peninsular 
  gneiss 
  rather 
  more, 
  and 
  those 
  of 
  the 
  

   Closepet 
  granite 
  the 
  greatest 
  variation. 
  

  

  The 
  auriferous 
  quartz 
  of 
  the 
  Kolar 
  Field 
  (No. 
  29) 
  is 
  inter- 
  

   esting 
  as 
  falling 
  into 
  line 
  with 
  the 
  members 
  of 
  the 
  Champion 
  

   gneiss 
  series, 
  with 
  which 
  it 
  has 
  been 
  correlated 
  on 
  other 
  

   grounds, 
  and, 
  as 
  already 
  pointed 
  out, 
  the 
  altered 
  schists 
  (lode 
  

   matter) 
  in 
  contact 
  with, 
  or 
  in 
  continuation 
  of, 
  the 
  auriferous 
  

   quartz 
  veins 
  show 
  values 
  intermediate 
  between 
  those 
  of 
  the 
  

   normal 
  schists 
  and 
  of 
  the 
  quartz. 
  

  

  It 
  is 
  interesting 
  also 
  to 
  note 
  that 
  the 
  matrix 
  of 
  the 
  Con- 
  

   glomerate 
  (No. 
  27) 
  has 
  the 
  same 
  radioactivity 
  as 
  the 
  clearly 
  

   intrusive 
  granite 
  (No. 
  28), 
  and 
  this 
  is 
  in 
  accordance 
  with 
  the 
  

   view 
  that 
  the 
  conglomerate 
  is 
  autoclastic 
  and 
  due 
  to 
  crushing 
  

   of 
  portions 
  of 
  the 
  Champion 
  gneiss 
  series. 
  

  

  The 
  pegmatite 
  cross-course 
  (No. 
  39) 
  is 
  remarkable 
  as 
  

   yielding 
  the 
  highest 
  result 
  so 
  far 
  obtained. 
  The 
  pegmatite 
  

   contains 
  a 
  large 
  amount 
  or 
  tourmaline, 
  and 
  it 
  was 
  thought 
  

   that 
  this 
  mineral 
  might 
  account 
  for 
  the 
  high 
  value. 
  A 
  small 
  

   quantity 
  of 
  the 
  tourmaline 
  was 
  separated 
  and, 
  though 
  a 
  

   definite 
  determination 
  was 
  not 
  made, 
  the 
  test 
  was 
  sufficient 
  

   to 
  show 
  that 
  it 
  was 
  not 
  abnormally 
  high, 
  and 
  that 
  the 
  high 
  

   result 
  of 
  the 
  rock 
  as 
  a 
  whole 
  was 
  not 
  due 
  to 
  this 
  mineral. 
  

  

  A 
  single 
  determination 
  (No. 
  50) 
  has 
  been 
  made 
  of 
  one 
  of 
  

   the 
  very 
  numerous 
  dolerite 
  dykes 
  which 
  are 
  considered 
  to 
  be 
  

   of 
  Pre-Cambrian 
  age 
  but 
  subsequent 
  to 
  the 
  formation 
  and 
  

   folding 
  of 
  the 
  Archaean 
  complex. 
  This 
  rock 
  is 
  very 
  similar 
  

   in 
  composition 
  to 
  the 
  old 
  hornblendic 
  schists, 
  which 
  probably 
  

   were 
  originally 
  diabasic 
  flows 
  and 
  sills 
  of 
  a 
  much 
  earlier 
  

   period. 
  The 
  result 
  shows 
  that 
  the 
  later 
  rock 
  contains 
  more 
  

   than 
  twice 
  as 
  much 
  radium 
  as 
  the 
  earlier 
  type, 
  but 
  no 
  further 
  

   inference 
  can 
  be 
  drawn 
  from 
  a 
  single 
  observation. 
  

  

  Summary. 
  

  

  1. 
  These 
  very 
  ancient 
  rocks, 
  all 
  of 
  which 
  are 
  considered 
  

   to 
  be 
  of 
  igneous 
  origin, 
  contain 
  remarkably 
  little 
  radium. 
  

  

  2. 
  Amongst 
  the 
  various 
  groups 
  which 
  have 
  been 
  differ- 
  

   entiated 
  on 
  geological 
  grounds, 
  there 
  are 
  some 
  striking- 
  

   differences 
  in 
  the 
  radium 
  contents 
  of 
  some 
  of 
  them. 
  

  

  3. 
  In 
  the 
  case 
  of 
  a 
  fairly 
  uniform 
  group 
  of 
  rocks 
  (viz., 
  the 
  

   hornblendic 
  schists 
  of 
  the 
  Kolar 
  Field) 
  the 
  radium 
  content 
  

   does 
  not 
  appear 
  to 
  vary 
  with 
  the 
  depth 
  from 
  the 
  surface. 
  

  

  4. 
  Different 
  igneous 
  magmas 
  appear 
  to 
  contain 
  very 
  

   different 
  amounts 
  of 
  radium, 
  and 
  the 
  latter, 
  or 
  the 
  minerals 
  

  

  