﻿1875.] 
  Mr. 
  I. 
  L. 
  Bell 
  on 
  Changes 
  in 
  Basaltic 
  Veins. 
  54-3 
  

  

  XIV. 
  <( 
  On 
  some 
  supposed 
  changes 
  Basaltic 
  Veins 
  have 
  suffered 
  

   during 
  their 
  passage 
  through 
  and 
  contact 
  with 
  Stratified 
  Rocks, 
  

   and 
  on 
  the 
  manner 
  in 
  which 
  these 
  Bocks 
  have 
  been 
  affected 
  

   by 
  the 
  heated 
  Basalt/' 
  By 
  I, 
  Lowthian 
  Bell, 
  F.R.S. 
  Re- 
  

   ceived 
  May 
  27, 
  1875. 
  

  

  The 
  northern 
  counties 
  of 
  England 
  afford 
  very 
  satisfactory 
  evidence 
  of 
  

   the 
  intrusion, 
  in 
  former 
  geological 
  times, 
  of 
  a 
  large 
  area 
  of 
  fused 
  matter 
  

   beneath 
  portions 
  of 
  the 
  then-existing 
  surface, 
  and 
  through 
  the 
  vertical, 
  

   or 
  nearly 
  vertical, 
  faults 
  and 
  fissures 
  of 
  thin 
  sedimentary 
  strata. 
  

  

  Through 
  the 
  observations 
  and 
  writings 
  of 
  N. 
  J. 
  Winch*, 
  Sir 
  Walter 
  

   Trevelyanf 
  , 
  Prof. 
  Sedgwick 
  t, 
  William 
  Hutton§, 
  John 
  Buddie 
  ||, 
  Nicholas 
  

   Wood 
  If, 
  Westgarth 
  Forster**, 
  and 
  several 
  other 
  observers 
  of 
  earlier 
  tf 
  and 
  

   more 
  recent 
  J 
  t 
  date, 
  we 
  have 
  been 
  made 
  acquainted 
  with 
  many 
  details 
  of 
  

   the 
  existence, 
  appearance, 
  and 
  direction 
  at 
  the 
  surface 
  of 
  extensive 
  

   whin-dykes 
  and 
  beds 
  of 
  intercalated 
  trap, 
  basalt, 
  or 
  whin, 
  using 
  the 
  

   terms 
  which 
  have 
  hitherto 
  been 
  generally 
  and 
  locally 
  applied 
  to 
  the 
  

   igneous 
  rocks 
  found 
  in 
  connexion 
  with 
  the 
  Carboniferous 
  formation 
  of 
  

   these 
  districts. 
  

  

  In 
  the 
  most 
  northerly 
  part 
  of 
  Northumberland 
  a 
  broad 
  dyke 
  of 
  igneous 
  

   rock 
  occurs 
  on 
  Holy 
  Island, 
  and 
  is 
  continued 
  on 
  the 
  mainland 
  to 
  the 
  

   west. 
  Several 
  other 
  dykes, 
  too 
  numerous, 
  indeed, 
  to 
  be 
  specially 
  men- 
  

   tioned 
  in 
  this 
  communication, 
  occur 
  in 
  the 
  Carboniferous 
  rocks 
  between 
  

   this 
  locality 
  and 
  the 
  banks 
  of 
  the 
  Tees, 
  having 
  for 
  the 
  most 
  part 
  a 
  direc- 
  

   tion 
  from 
  west 
  to 
  east. 
  In 
  addition 
  to 
  the 
  dykes 
  which 
  may 
  have 
  filled 
  

   up 
  old 
  lines 
  of 
  faults 
  and 
  fissures, 
  we 
  have 
  bedded 
  igneous 
  rocks, 
  where 
  

   fused 
  matter, 
  instead 
  of 
  coming 
  to 
  the 
  surface, 
  has 
  forced 
  its 
  passage 
  or 
  

   way, 
  horizontally 
  between 
  the 
  regular 
  and 
  previously 
  stratified 
  sedimentary 
  

   rocks. 
  Sometimes 
  also 
  the 
  igneous 
  matter 
  is 
  found 
  between 
  the 
  central 
  

   portions 
  of 
  individual 
  beds 
  of 
  shale 
  and 
  limestone, 
  and 
  in 
  its 
  course 
  has 
  

   oftentimes 
  enclosed 
  in 
  its 
  mass 
  considerable 
  portions 
  of 
  such 
  preexisting 
  

   beds, 
  as 
  in 
  the 
  examples 
  figured 
  by 
  Prof. 
  Sedgwick 
  in 
  the 
  second 
  volume 
  

   of 
  the 
  Cambridge 
  Philosophical 
  Transactions. 
  

  

  * 
  Trans. 
  Geol. 
  Soc. 
  1814, 
  vol. 
  iv. 
  pp. 
  21 
  & 
  73. 
  

  

  t 
  Wernerian 
  Soc. 
  Memoirs, 
  1821-23, 
  p. 
  253, 
  and 
  Trans. 
  Nat. 
  Hist. 
  Soc. 
  Northumber- 
  

   land 
  and 
  Durham, 
  1830, 
  vol. 
  i. 
  p. 
  58. 
  

  

  t 
  Cambridge 
  Phil. 
  Trans, 
  vol. 
  ii. 
  pp. 
  21 
  & 
  139. 
  

  

  § 
  Trans. 
  Nat. 
  Hist. 
  Soc. 
  Northumberland 
  and 
  Durham, 
  1831, 
  vol. 
  ii. 
  p. 
  187. 
  

  

  || 
  Ibid. 
  1830, 
  vol. 
  i. 
  p. 
  9. 
  

  

  % 
  Ibid. 
  1831, 
  vol. 
  i. 
  p. 
  327. 
  

  

  ** 
  Section 
  of 
  the 
  Strata 
  &c, 
  1821. 
  

  

  tt 
  Hon. 
  H. 
  a. 
  Bennett, 
  M.P., 
  F.R.S., 
  Geol. 
  Trans. 
  1812, 
  vol. 
  iv. 
  p. 
  102 
  ; 
  Conybeare 
  

   and 
  Phillips, 
  Geol. 
  of 
  England 
  and 
  Wales, 
  1821, 
  pt. 
  1 
  ; 
  Michael 
  Forster, 
  Trans. 
  Nat. 
  

   Hist. 
  Soc. 
  Northumberland 
  and 
  Durham, 
  1830, 
  vol. 
  i. 
  p. 
  44; 
  Francis 
  Forster, 
  ibid 
  

   p. 
  75 
  ; 
  Henry 
  T. 
  M. 
  Witham, 
  ibid, 
  vol. 
  ii. 
  p. 
  343. 
  

  

  tt 
  George 
  Tate, 
  Trans. 
  Tyneside 
  Nat.-Hist. 
  Field-Club, 
  vol. 
  ii. 
  new 
  series. 
  

   VOL. 
  XXIII. 
  2 
  T 
  

  

  