﻿

  ASHPRINGTON 
  VOLCANIC 
  SERIES 
  OE 
  SOUTH 
  DEVON. 
  371 
  

  

  loidal 
  kernels 
  interspersed. 
  At 
  a 
  small 
  quarry 
  above 
  Allabeer 
  on 
  

   the 
  right 
  bank 
  of 
  the 
  Dart 
  and 
  elsewhere 
  some 
  purplish 
  and 
  

   yellowish 
  flecked 
  shales 
  are 
  seen, 
  the 
  paler 
  patches 
  having 
  a 
  steatitic 
  

   aspect. 
  

  

  Again, 
  the 
  lavas 
  are 
  often 
  highly 
  calcareous, 
  probably 
  from 
  sub- 
  

   sequent 
  infiltration, 
  and 
  as 
  they 
  are 
  both 
  aphanitic 
  and 
  sometimes 
  

   flaggy, 
  as 
  above 
  mentioned, 
  they 
  appear 
  (without 
  always 
  assigning 
  

   definite 
  names, 
  such 
  as 
  " 
  porphyrite 
  " 
  or 
  " 
  basalt," 
  to 
  rocks 
  which 
  

   are 
  so 
  highly 
  altered) 
  to 
  correspond 
  to 
  descriptions 
  of 
  " 
  slaty 
  calc- 
  

   aphanites," 
  even 
  leading 
  towards 
  " 
  schalsteins." 
  

  

  Of 
  the 
  fact 
  of 
  such 
  alteration, 
  the 
  microscope 
  leaves 
  no 
  room 
  for 
  

   doubt. 
  The 
  felspars 
  are 
  blurred, 
  as 
  if 
  changing 
  to 
  saussurite, 
  like 
  

   the 
  felspars 
  in 
  the 
  Lizard 
  gabbros 
  ; 
  or 
  they 
  exhibit 
  a 
  veined 
  appearance. 
  

   Some 
  unaltered 
  augite 
  is 
  usually 
  present, 
  as 
  also 
  a 
  plentiful 
  sprinkling 
  

   of 
  magnetite 
  or 
  ilmenite 
  ; 
  but 
  owing 
  to 
  the 
  extent 
  of 
  alteration 
  the 
  

   thinnest 
  sections 
  let 
  very 
  little 
  light 
  pass. 
  

  

  Nowhere 
  do 
  true 
  grits 
  appear 
  to 
  form 
  any 
  part 
  of 
  this 
  series 
  ; 
  it 
  

   is 
  somewhat 
  perplexing 
  that 
  the 
  purple 
  grits 
  of 
  Cockington, 
  Beacon 
  

   Hill, 
  and 
  Windmill 
  Hill, 
  which 
  support 
  the 
  Triassic 
  rocks 
  of 
  

   Paignton, 
  do 
  not 
  apparently 
  extend 
  across 
  the 
  Dart 
  between 
  Totnes 
  

   and 
  Sharpham, 
  as 
  the 
  same 
  beds 
  do 
  south 
  of 
  Greenway 
  and 
  Ditti- 
  

   sham. 
  However, 
  with 
  the 
  exception 
  of 
  a 
  narrow 
  strip 
  which 
  

   appears 
  to 
  be 
  thrown 
  down 
  by 
  a 
  fault, 
  and 
  some 
  beds 
  at 
  Langcombe 
  

   Farm, 
  they 
  certainly 
  form 
  no 
  feature 
  south-west 
  of 
  a 
  line 
  extending 
  

   from 
  Langcombe 
  Cross 
  to 
  Stoke 
  Gabriel. 
  There 
  are 
  some 
  signs 
  of 
  

   a 
  N.W. 
  and 
  S.E. 
  fracture 
  bearing 
  south-easterly 
  for 
  many 
  miles, 
  and 
  

   its 
  existence 
  between 
  the 
  south-west 
  of 
  Ash 
  and 
  Stoke 
  Gabriel 
  was 
  

   mentioned 
  by 
  Dr. 
  Holl. 
  If 
  these 
  strips 
  really 
  belong 
  to 
  the 
  slaty 
  

   beds 
  at 
  the 
  base 
  of 
  the 
  Cockington 
  grits, 
  then 
  they 
  overlie 
  the 
  

   volcanic 
  series, 
  and 
  are 
  thrown 
  down 
  by 
  faults 
  sensibly 
  at 
  right 
  

   angles 
  to 
  the 
  one 
  just 
  named, 
  but 
  they 
  disappear 
  before 
  reaching 
  

   the 
  Dart. 
  

  

  Were 
  it 
  not 
  that 
  the 
  greenish 
  aphanitic 
  rocks 
  can 
  be 
  actually 
  

   observed 
  passing 
  to 
  a 
  deep 
  red, 
  the 
  outlines 
  of 
  the 
  felspars 
  being 
  

   still 
  traceable, 
  one 
  might 
  be 
  inclined 
  to 
  regard 
  all 
  the 
  soft, 
  raddled, 
  

   earthy-looking 
  rocks 
  as 
  tuffs 
  ; 
  but 
  for 
  the 
  reason 
  just 
  stated 
  we 
  

   could 
  not 
  safely 
  do 
  so. 
  The 
  quantity 
  of 
  magnetite 
  or 
  ilmenite 
  

   which 
  appears 
  in 
  every 
  section 
  I 
  have 
  had 
  cut 
  would 
  furnish 
  a 
  

   ready 
  source 
  for 
  any 
  degree 
  of 
  peroxidation 
  ; 
  some 
  sections, 
  when 
  

   seen 
  by 
  reflected 
  light, 
  show 
  these 
  specks 
  turned 
  brown, 
  and 
  when 
  

   this 
  destructive 
  process 
  is 
  carried 
  far 
  enough, 
  all 
  distinctive 
  cha- 
  

   racters 
  of 
  the 
  rock 
  are 
  lost. 
  These 
  decomposed 
  rocks 
  generally 
  

   yield 
  freely 
  to 
  the 
  knife, 
  differing 
  in 
  this 
  respect 
  altogether 
  from 
  

   grits 
  of 
  Devonian 
  age. 
  

  

  Iron-ores, 
  both 
  haematite 
  and 
  limonite, 
  are 
  occasionally 
  found 
  

   among 
  the 
  red 
  rocks, 
  as 
  we 
  might 
  naturally 
  expect, 
  but 
  their 
  mode 
  

   of 
  occurrence 
  is 
  apparently 
  so 
  capricious 
  that 
  they 
  have 
  never 
  been 
  

   profitably 
  worked 
  for 
  any 
  length 
  of 
  time. 
  I 
  am 
  indebted 
  to 
  Dr. 
  

   Pridham 
  for 
  information 
  on 
  this 
  point. 
  In 
  Cornworthy 
  parish, 
  on 
  

   each 
  side 
  of 
  the 
  lane 
  leading 
  north-east 
  from 
  the 
  village 
  to 
  Tuckenhay 
  

  

  2e 
  2 
  

  

  