﻿466 
  PROCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  [June 
  22, 
  

  

  this 
  trap 
  is 
  not 
  met 
  with 
  until 
  two 
  -thirds 
  of 
  the 
  ascent 
  is 
  

   gained. 
  After 
  walking 
  over 
  New 
  Red 
  Sandstone, 
  which 
  is 
  quite 
  

   bare 
  for 
  several 
  hundred 
  yards, 
  we 
  come 
  to 
  where 
  the 
  soil 
  is 
  suffi- 
  

   ciently 
  deep 
  for 
  the 
  growth 
  of 
  scrub. 
  Crossing 
  a 
  steep 
  valley 
  of 
  

   dislocation, 
  which 
  is 
  densely 
  overgrown 
  with 
  underwood, 
  we 
  have 
  

   before 
  us 
  the 
  abrupt 
  acclivity 
  of 
  this 
  hill 
  ; 
  and 
  at 
  every 
  fifty 
  paces 
  

   or 
  so 
  immense 
  blocks 
  of 
  sandstone 
  are 
  met 
  with, 
  having 
  been 
  re- 
  

   moved 
  from 
  the 
  parent 
  mass 
  by 
  landslips 
  ; 
  while 
  a 
  little 
  higher 
  up 
  

   there 
  are 
  several 
  quarries 
  in 
  the 
  sandstone, 
  most 
  of 
  which 
  are 
  being 
  

   worked. 
  As 
  yet, 
  not 
  a 
  vestige 
  of 
  trap 
  is 
  seen 
  ; 
  but 
  when 
  about 
  two- 
  

   thirds 
  of 
  the 
  way 
  to 
  the 
  top, 
  it 
  is 
  seen 
  in 
  small 
  fragments, 
  inter- 
  

   mingled 
  with 
  sandstone-rubble. 
  A 
  few 
  yards 
  nearer 
  the 
  summit, 
  

   and 
  the 
  sandstone 
  is 
  no 
  longer 
  visible, 
  but 
  in 
  its 
  stead 
  large 
  masses 
  

   of 
  half-decomposed 
  trap 
  are 
  found, 
  with 
  which 
  the 
  top 
  of 
  the 
  hill 
  is 
  

   covered, 
  amid 
  the 
  densest 
  vegetation 
  imaginable. 
  

  

  There 
  are 
  no 
  less 
  than 
  forty- 
  eight 
  of 
  these 
  trappean 
  outbursts 
  

   within 
  a 
  circuit 
  of 
  ten 
  miles, 
  plainly 
  showing 
  that 
  at 
  a 
  comparatively 
  

   recent 
  period 
  (say, 
  the 
  Tertiary) 
  the 
  area 
  contained 
  within 
  these 
  

   limits 
  must 
  have 
  been 
  the 
  seat 
  of 
  intense 
  volcanic 
  action, 
  though 
  for 
  

   the 
  most 
  part 
  at 
  a 
  considerable 
  depth 
  beneath 
  the 
  surface 
  of 
  the 
  sea, 
  

   for 
  I 
  have 
  not 
  been 
  able 
  to 
  detect 
  any 
  volcanic 
  ashes 
  or 
  scoriae. 
  

  

  A 
  dyke 
  of 
  trap 
  has 
  lately 
  been 
  exposed 
  in 
  a 
  road-cutting 
  about 
  

   100 
  yards 
  from 
  a 
  coal-shaft 
  at 
  New 
  Town. 
  It 
  is 
  about 
  twenty 
  yards 
  

   wide, 
  and 
  has 
  burst 
  through 
  the 
  Carboniferous 
  Sandstone, 
  which 
  im- 
  

   mediately 
  overlies 
  the 
  coal, 
  or 
  rather 
  slaty 
  anthracite, 
  to 
  the 
  depth 
  

   of 
  80 
  feet. 
  On 
  either 
  side 
  of 
  this 
  dyke 
  there 
  is 
  a 
  soft 
  pulverulent 
  soil 
  

   of 
  a 
  dull 
  lead-colour, 
  like 
  that 
  of 
  the 
  sandstone, 
  about 
  a 
  foot 
  and 
  a 
  

   half 
  wide, 
  and 
  traversed 
  by 
  veins 
  of 
  what 
  I 
  am 
  inclined 
  to 
  think 
  is 
  

   a 
  sulphate 
  of 
  lime*. 
  "Whether 
  this 
  loose 
  incoherent 
  mass 
  is 
  the 
  

   effect 
  of 
  the 
  molten 
  trap 
  on 
  the 
  sandstone, 
  or 
  not, 
  I 
  cannot 
  say. 
  

   The 
  sandstone, 
  however, 
  must 
  necessarily 
  have 
  been 
  subjected 
  to 
  an 
  

   intense 
  degree 
  of 
  heat 
  at 
  the 
  time 
  of 
  the 
  intrusion, 
  and 
  therefore 
  one 
  

   would 
  be 
  led 
  to 
  expect 
  that 
  that 
  portion 
  of 
  the 
  sandstone 
  in 
  contact 
  

   with 
  the 
  igneous 
  matter 
  would 
  present 
  more 
  of 
  a 
  vitrified 
  appearance 
  

   than 
  otherwise 
  ; 
  but 
  the 
  reverse 
  is 
  the 
  fact. 
  

  

  There 
  is 
  one 
  singular 
  description 
  of 
  trap 
  -rock 
  which 
  is 
  seen 
  on 
  the 
  

   banks 
  of 
  the 
  Derwent, 
  two 
  or 
  three 
  miles 
  below 
  the 
  city, 
  and 
  which 
  

   constitutes 
  a 
  formation 
  of 
  a 
  quarter 
  of 
  a 
  mile 
  in 
  width, 
  and 
  100 
  feet 
  

   in 
  depth. 
  Where 
  the 
  action 
  of 
  the 
  water 
  has 
  eaten 
  it 
  away, 
  thereby 
  

   forming 
  a 
  cliff, 
  it 
  is 
  seen 
  reposing 
  upon 
  a 
  reef 
  of 
  very 
  beautiful 
  

   haematite, 
  which 
  extends 
  several 
  miles 
  in 
  a 
  north-easterly 
  direction 
  f. 
  

   In 
  some 
  parts 
  this 
  rock 
  bears 
  the 
  appearance 
  of 
  very 
  vesicular 
  

   lava, 
  rather 
  than 
  a 
  modified 
  ordinary 
  trap, 
  and 
  is 
  found 
  entirely 
  

   devoid 
  of 
  the 
  white 
  mineral 
  which 
  in 
  many 
  places 
  composes 
  its 
  chief 
  

   constituent, 
  and 
  which 
  I 
  think 
  is 
  a 
  crystallized 
  carbonate 
  of 
  lime. 
  

   I 
  have 
  traced 
  it 
  for 
  a 
  distance 
  of 
  four 
  and 
  a 
  half 
  miles, 
  the 
  river 
  appa- 
  

   rently 
  flowing 
  through 
  its 
  centre, 
  when 
  it 
  is 
  cut 
  off 
  at 
  either 
  end 
  by 
  

  

  * 
  See 
  specimen 
  .No. 
  4, 
  Coll. 
  Geol. 
  Soc. 
  

  

  t 
  See 
  specimens 
  Nos. 
  5 
  & 
  6, 
  Coll. 
  Geol. 
  Soc. 
  

  

  