﻿490 
  MESSRS. 
  E. 
  T. 
  NEWTON" 
  AND 
  J. 
  J. 
  H. 
  TEALL 
  ON 
  [Dec. 
  1 
  89 
  7, 
  

  

  We 
  cannot, 
  therefore, 
  separate 
  the 
  specimens 
  into 
  two 
  groups, 
  

   lavas 
  and 
  intrusive 
  sills. 
  Nansen 
  speaks: 
  of 
  basalt 
  interstratined 
  with 
  

   the 
  underlying 
  sediments, 
  and 
  the 
  collection 
  that 
  we 
  are 
  describing 
  

   contains 
  specimens 
  of 
  amygdaloidal 
  basalt 
  ' 
  from 
  lowest 
  rock 
  (6 
  feet 
  

   deep) 
  having 
  3 
  feet 
  layer 
  of 
  sandstone 
  above 
  it.' 
  They 
  were 
  col- 
  

   lected 
  from 
  the 
  watercourse 
  running 
  down 
  the 
  talus. 
  It 
  is 
  a 
  well- 
  

   known 
  fact 
  that 
  the 
  basalts 
  of 
  the 
  West 
  of 
  Scotland 
  are 
  often 
  

   intercalated 
  between 
  Jurassic 
  strata, 
  1 
  and 
  this 
  fact 
  led 
  the 
  early 
  

   observers 
  to 
  conclude 
  that 
  they 
  were 
  of 
  Jurassic 
  age 
  ; 
  but 
  it 
  is 
  now 
  

   universally 
  admitted 
  that 
  this 
  intercalation 
  is 
  the 
  result 
  of 
  intrusion 
  

   along 
  planes 
  of 
  bedding, 
  and 
  that 
  the 
  basalts 
  in 
  question 
  are 
  post- 
  

   Cretaceous. 
  

  

  The 
  existence 
  of 
  tuft's 
  cannot 
  be 
  positively 
  asserted 
  from 
  the 
  

   evidence 
  before 
  us, 
  but 
  there 
  are 
  one 
  or 
  two 
  specimens 
  of 
  highly 
  

   altered 
  rocks 
  which 
  may 
  be 
  tuffs. 
  The 
  evidence 
  that 
  pauses 
  occurred 
  

   during 
  the 
  formation 
  of 
  the 
  plateau-basalts 
  is 
  of 
  a 
  more 
  satisfactory 
  

   character. 
  This 
  is 
  furnished 
  by 
  a 
  specimen 
  of 
  a 
  conglomeratic 
  rock, 
  

   mainly 
  composed 
  of 
  basaltic 
  debris 
  and 
  containing 
  rounded 
  pebbles, 
  

   ' 
  found 
  in 
  dolerite 
  some 
  50 
  feet 
  above 
  lowest 
  rock' 
  near 
  Cape 
  Flora. 
  

  

  We 
  are 
  indebted 
  to 
  Mr. 
  Fisher 
  for 
  the 
  following 
  table, 
  giving 
  

   the 
  lowest 
  level 
  at 
  which 
  the 
  main 
  mass 
  of 
  basalt 
  could 
  be 
  seen 
  at 
  

   several 
  localities 
  ; 
  the 
  base, 
  however, 
  was 
  often 
  hidden 
  by 
  talus 
  : 
  — 
  

  

  feet. 
  

  

  Cape 
  Flora 
  600 
  

  

  Cape 
  Gertrude 
  700 
  

  

  Cape 
  Stephen 
  650 
  

  

  Tween 
  Rocks 
  450 
  at 
  one 
  place, 
  200 
  at 
  

  

  another. 
  

  

  Cape 
  Grant 
  400 
  to 
  500 
  

  

  Cape 
  Crow 
  the 
  i- 
  700 
  on 
  one 
  side, 
  and 
  sea- 
  

   level 
  on 
  the 
  other. 
  

   Cape 
  Neale 
  500 
  

  

  IV. 
  Distribution 
  of 
  Basalts 
  oe 
  similar 
  Type. 
  

  

  We 
  will 
  now 
  conclude 
  this 
  account 
  of 
  the 
  ordinary 
  basalts 
  with 
  

   some 
  remarks 
  on 
  the 
  general 
  distribution 
  of 
  rocks 
  of 
  the 
  same 
  type. 
  

   Specimens 
  brought 
  home 
  by 
  Payer 
  were 
  described 
  by 
  Prof. 
  

   Tschermak. 
  He 
  says, 
  * 
  It 
  [the 
  dolerite] 
  is 
  a 
  medium- 
  giained, 
  dark 
  

   yellowish-green, 
  crystalline, 
  massive 
  rock. 
  Plagioclase 
  forms 
  the 
  

   principal 
  mass, 
  although 
  it 
  only 
  exceeds 
  the 
  angite 
  by 
  a 
  small 
  

   amount. 
  The 
  crystals 
  of 
  plagioclase 
  are 
  frequently 
  1 
  mm., 
  some- 
  

   times 
  3 
  mm. 
  long. 
  They 
  consist 
  sometimes 
  of 
  thin 
  and 
  sometimes 
  

   of 
  thick 
  lamellae. 
  The 
  augite 
  is 
  greenish 
  grey, 
  shows 
  no 
  crystalline 
  

   outlines, 
  but 
  forms 
  grains 
  which 
  are 
  often 
  1 
  mm. 
  in 
  diameter. 
  

   Inclusions 
  of 
  the 
  other 
  minerals 
  are 
  frequent, 
  and 
  also 
  gas-pores. 
  

   Olivine 
  forms 
  grains 
  which 
  are 
  smaller 
  than 
  the 
  augite 
  and 
  only 
  

   seldom 
  show 
  crystalline 
  faces. 
  These 
  grains 
  are 
  frequently 
  sur- 
  

   rounded 
  with 
  a 
  border 
  of 
  a 
  yellowish-brown 
  mineral 
  (eisenchlorit). 
  

   The 
  titaniferous 
  iron-ore 
  occurs 
  in 
  long 
  plates 
  or 
  fills 
  the 
  space 
  

  

  1 
  Sir 
  A. 
  Geikie, 
  op. 
  cit. 
  p. 
  375. 
  

  

  