﻿1875.] 
  r 
  ^supposed 
  Changes 
  in 
  Basaltic 
  Veins, 
  

  

  545 
  

  

  In 
  the 
  meantime 
  a 
  neighbouring 
  firm 
  had 
  sunk 
  a 
  pit 
  in 
  the 
  immediate 
  

   vicinity 
  without 
  meeting 
  with 
  any 
  trace 
  of 
  whin 
  rock; 
  and 
  as 
  circum- 
  

   stances 
  demanded 
  it, 
  two 
  shafts 
  were 
  commenced 
  by 
  Messrs. 
  Bell 
  Brothers 
  

   185 
  yards 
  N.E. 
  of 
  the 
  first 
  bore-hole. 
  The 
  area 
  within 
  these 
  three 
  points 
  

   amounts 
  to 
  something 
  like 
  15 
  acres. 
  When 
  the 
  more 
  advanced 
  of 
  these 
  

   pits 
  was 
  sunk 
  to 
  a 
  depth 
  of 
  67 
  fathoms, 
  the 
  men 
  came 
  upon 
  the 
  hard 
  

   obstacle 
  met 
  with 
  in 
  the 
  bore-holes 
  ; 
  and 
  the 
  same 
  thing 
  happened 
  in 
  

   the 
  second 
  shaft, 
  situate 
  60 
  yards 
  to 
  the 
  west 
  of 
  its 
  neighbour. 
  

  

  In 
  each 
  case 
  fully 
  four 
  months 
  of 
  incessant 
  labour, 
  accompanied 
  with 
  

   considerable 
  expense, 
  was 
  required 
  before 
  the 
  lower 
  surface 
  of 
  this 
  hard 
  

   stratum 
  was 
  reached, 
  which 
  proved 
  to 
  have 
  a 
  thickness 
  of 
  19* 
  75 
  feet. 
  

   In 
  all 
  probability, 
  however, 
  its 
  dimensions 
  are 
  subject 
  to 
  considerable 
  

   fluctuations, 
  for 
  in 
  one 
  of 
  these 
  two 
  pits 
  the 
  bed 
  is 
  4 
  feet 
  thinner 
  on 
  the 
  

   north 
  side 
  of 
  the 
  shaft 
  than 
  on 
  the 
  south. 
  

  

  It 
  was 
  now 
  clear 
  that 
  it 
  was 
  a 
  bed 
  of 
  basalt 
  lying 
  in 
  a 
  horizontal 
  posi- 
  

   tion 
  which 
  was 
  encountered, 
  hi 
  which 
  direction 
  it 
  had 
  spread 
  itself 
  as 
  one 
  

   offering 
  less 
  resistance 
  than 
  that 
  to 
  be 
  overcome 
  by 
  forcing 
  an 
  exit 
  at 
  the 
  

   surface. 
  At 
  what 
  point 
  a 
  communication 
  exists 
  between 
  this 
  interjected 
  

   mass 
  and 
  its 
  subterranean 
  source 
  we 
  have 
  had 
  no 
  means 
  of 
  ascer- 
  

   taining. 
  

  

  Above 
  and 
  below 
  the 
  basaltic 
  bed, 
  as 
  found 
  in 
  the 
  pits, 
  there 
  are 
  two 
  

   well-known 
  seams 
  of 
  coal. 
  In 
  the 
  neighbouring 
  colliery 
  spoken 
  of 
  

   (Littleburn) 
  these 
  are 
  separated 
  by 
  50*25 
  feet 
  of 
  fire-clays, 
  shales, 
  and 
  

   sandstones, 
  while 
  in 
  the 
  present 
  case 
  the 
  intervening 
  rocks 
  measure 
  

   103*66 
  feet, 
  showing 
  an 
  increase 
  of 
  53*41 
  feet. 
  Of 
  this 
  only 
  19*75 
  feet 
  

   is 
  due 
  to 
  the 
  whin, 
  the 
  remaining 
  33*66 
  feet 
  arising 
  from 
  a 
  thickening 
  

   of 
  the 
  sandstone 
  and 
  other 
  deposits. 
  

  

  During 
  the 
  entire 
  progress 
  of 
  sinking 
  specimens 
  of 
  the 
  rocks 
  were 
  

   preserved, 
  which 
  enabled 
  me 
  at 
  my 
  leisure 
  to 
  examine 
  not 
  only 
  the 
  whin 
  

   but 
  also 
  the 
  altered 
  character 
  of 
  the 
  adjacent 
  strata. 
  

  

  The 
  change 
  experienced 
  by 
  the 
  latter 
  has 
  frequently 
  formed 
  the 
  sub- 
  

   ject 
  of 
  comment 
  ; 
  but 
  I 
  am 
  not 
  aware 
  that 
  much 
  attention 
  has 
  been 
  

   directed 
  to 
  any 
  modification 
  in 
  the 
  composition 
  of 
  the 
  basalt 
  itself, 
  

   caused 
  by 
  contact 
  with 
  the 
  substances 
  through 
  which 
  it 
  had 
  pene- 
  

   trated. 
  

  

  It 
  would 
  of 
  course 
  be 
  highly 
  instructive 
  if 
  any 
  sedimentary 
  rock 
  could 
  

   be 
  accepted, 
  in 
  respect 
  to 
  its 
  constituents 
  and 
  their 
  relations 
  to 
  each 
  

   other, 
  as 
  a 
  normal 
  type 
  of 
  whinstone. 
  If, 
  for 
  example, 
  an 
  aqueous 
  

   rock 
  were 
  found 
  in 
  the 
  immediate 
  vicinity 
  of 
  basalt, 
  and 
  the 
  compositions 
  

   of 
  both 
  were 
  the 
  same, 
  one 
  might 
  infer 
  the 
  physical 
  difference 
  to 
  be 
  due 
  

   to 
  the 
  mere 
  influence 
  of 
  igneous 
  action. 
  

  

  There 
  are, 
  however, 
  to 
  be 
  found 
  in 
  nature 
  many 
  substances 
  which 
  

   more 
  or 
  less 
  resemble 
  in 
  constitution 
  the 
  matter 
  filling 
  whin-dykes, 
  clay- 
  

   slate 
  being 
  one, 
  some 
  specimens 
  of 
  which 
  contain 
  the 
  following 
  ingre- 
  

   dients 
  : 
  — 
  

  

  2 
  t 
  2 
  

  

  