﻿492 
  MESSRS. 
  E. 
  T. 
  NEWTON 
  AND 
  J. 
  J. 
  H. 
  TEALL 
  ON 
  [Dec. 
  1897, 
  

  

  importance 
  ; 
  it 
  is 
  certain, 
  however, 
  from 
  Drasche's 
  description 
  that 
  

   some 
  of 
  them 
  are 
  substantially 
  identical 
  with 
  rocks 
  described 
  as 
  

   basalt 
  from 
  other 
  portions 
  of 
  the 
  Brito-A.rctic 
  province. 
  It 
  is 
  often 
  

   not 
  clearly 
  recognized 
  by 
  Continental 
  authors 
  that 
  the 
  basalts 
  and 
  

   dolerites 
  of 
  this 
  province 
  are 
  more 
  closely 
  allied 
  in 
  composition 
  and 
  

   structure 
  to 
  the 
  pre-Tertiary 
  diabases 
  of 
  the 
  Continent 
  than 
  they 
  

   are 
  to 
  the 
  Tertiary 
  basalts 
  of 
  the 
  same 
  region. 
  We 
  may 
  safely 
  

   conclude 
  that 
  the 
  so-called 
  ' 
  diabases 
  ' 
  of 
  Spitsbergen 
  described 
  by 
  

   Drasche 
  are 
  of 
  the 
  same 
  general 
  character, 
  and 
  approximately 
  of 
  the 
  

   same 
  age, 
  as 
  the 
  basalts 
  of 
  .Franz 
  Josef 
  Land. 
  

  

  The 
  rocks 
  of 
  Jan 
  Mayen 
  have 
  been 
  described 
  by 
  Reuseh 
  l 
  and 
  

   Scharizer. 
  2 
  The 
  descriptions 
  of 
  these 
  authors 
  show 
  that 
  rocks 
  

   closely 
  allied 
  to 
  those 
  of 
  Franz 
  Josef 
  Land 
  occur 
  on 
  this 
  island. 
  

   Thus 
  Rensch 
  speaks 
  of 
  the 
  occurrence 
  in 
  one 
  of 
  the 
  specimens 
  

   examined 
  by 
  him 
  of 
  hollow 
  cavities 
  ' 
  en 
  compassed 
  by 
  a 
  zone 
  of 
  

   glass,' 
  and 
  Scharizerrecordsthe 
  presence 
  of 
  a 
  chrome-diopside. 
  In 
  the 
  

   British 
  Isles 
  the 
  rocks 
  which 
  most 
  closely 
  resemble 
  the 
  vesicular 
  

   basalts 
  of 
  Cape 
  Flora 
  are 
  those 
  of 
  Carnmoney 
  Hill, 
  near 
  Belfast, 
  

   and 
  of 
  Bunowen 
  Tower, 
  in 
  County 
  Galway. 
  3 
  Both 
  these 
  rocks 
  are 
  

   ophitic 
  dolerites 
  which 
  contain 
  brown 
  glass 
  or 
  its 
  hydrated 
  

   alteration 
  -product 
  (hullite). 
  The 
  rocks 
  of 
  the 
  Tynemouth 
  and 
  

   related 
  dykes 
  a 
  also 
  resemble 
  the 
  basalts 
  of 
  Franz 
  Josef 
  Land, 
  but 
  

   the 
  interstitial 
  matter 
  which 
  also 
  occurs 
  in 
  some 
  of 
  the 
  amygdules 
  

   is 
  always 
  devitrified. 
  

  

  It 
  is 
  evident, 
  therefore, 
  that 
  the 
  basalts 
  of 
  Cape 
  Flora 
  and 
  Hooker 
  

   Island 
  arc 
  similar 
  to 
  types 
  widely 
  distributed 
  in 
  the 
  Brito-Arctic 
  

   volcanic 
  province. 
  They 
  differ 
  from 
  the 
  more 
  common 
  noncrystalline 
  

   ophitic 
  dolerites 
  in 
  containing 
  a 
  small 
  quantity 
  of 
  interstitial 
  matter. 
  

   The 
  general 
  result 
  of 
  this 
  examination 
  is 
  to 
  confirm 
  the 
  conclusions 
  

   of 
  Payer, 
  Etheridge, 
  and 
  others 
  that 
  Franz 
  Josef 
  Land 
  belongs 
  

   geologically 
  to 
  an 
  extensive 
  region 
  of 
  plateau-basalts, 
  including 
  such 
  

   widely 
  separated 
  localities 
  as 
  Jan 
  Mayen. 
  Iceland, 
  Green 
  and, 
  the 
  

   Fseroe 
  Islands, 
  the 
  West 
  of 
  Scotland 
  and 
  the 
  North 
  of 
  Ireland. 
  

  

  The 
  second 
  type 
  of 
  basalt 
  is 
  represented 
  by 
  some 
  small 
  angular 
  

   fragments 
  obtained 
  from 
  the 
  underside 
  of 
  an 
  iceberg 
  in 
  De 
  Bruyne 
  

   Sound. 
  It 
  differs 
  from 
  the 
  common 
  type 
  above 
  described, 
  both 
  in 
  

   macroscopic 
  and 
  microscopic 
  characters, 
  and 
  is, 
  therefore, 
  considered 
  

   by 
  itself. 
  The 
  rock 
  is 
  dark 
  grey 
  in 
  colour, 
  compact, 
  and 
  of 
  so 
  tine 
  

   a 
  grain 
  that 
  extremely 
  thin 
  sections 
  and 
  high 
  powers 
  are 
  required 
  

   to 
  reveal 
  its 
  true 
  character. 
  The 
  specific 
  gravity 
  is 
  2*977. 
  The 
  

   principal 
  constituents 
  are 
  granules 
  and 
  microlites 
  of 
  augite 
  ('008 
  

   mm. 
  and 
  -008 
  x 
  -04 
  mm.), 
  microlites 
  of 
  felspar 
  (-004 
  x 
  "04), 
  and 
  

   crystals 
  or 
  grains 
  of 
  magnetite 
  (-008 
  x 
  '02). 
  4 
  It 
  is 
  possible 
  that 
  a 
  

  

  1 
  'Det 
  Norske 
  Nordhavs-Expedition, 
  1876-1878,' 
  Christiania, 
  1882, 
  p. 
  27. 
  

  

  2 
  ' 
  Ueber 
  Mineralien 
  u. 
  Gesteine 
  von 
  Jan 
  Mayen,' 
  Jahrb. 
  d.k.-k. 
  geol. 
  Eeichs- 
  

   anst. 
  vol. 
  xxxiv. 
  (1884) 
  p. 
  707. 
  

  

  3 
  See 
  papers, 
  already 
  quoted, 
  by 
  Profs. 
  Cole 
  and 
  Sollas. 
  

  

  . 
  4 
  The 
  figures 
  are 
  merely 
  intended 
  to 
  give 
  an 
  idea 
  of 
  the 
  scale 
  on 
  which 
  the 
  

   different 
  constituents 
  are 
  developed. 
  

  

  