﻿212 
  PROF. 
  E. 
  HULL 
  ON 
  THE 
  TWO 
  BRITISH 
  

  

  As 
  regards 
  the 
  base 
  of 
  the 
  Cambrian 
  beds, 
  that 
  is 
  well 
  defined 
  in 
  

   the 
  Highlands 
  ; 
  and 
  if 
  it 
  should 
  ultimately 
  appear 
  that 
  the 
  base 
  of 
  the 
  

   representative 
  beds 
  has 
  been 
  realty 
  discovered 
  in 
  Anglesey, 
  as 
  stated 
  

   by 
  Prof. 
  Hughes, 
  Dr. 
  Hicks, 
  and 
  Dr. 
  Callaway* 
  (a 
  point 
  on 
  which 
  I 
  

   have 
  no 
  opinion 
  to 
  offer), 
  then 
  the 
  lower, 
  as 
  well 
  as 
  the 
  upper, 
  limit 
  

   of 
  the 
  formation 
  here 
  described 
  will 
  have 
  been 
  well 
  determined 
  in 
  

   each 
  country. 
  

  

  Now 
  let 
  us 
  compare 
  these 
  presumed 
  representative 
  beds 
  as 
  they 
  

   occur 
  in 
  the 
  Highlands 
  of 
  Scotland, 
  in 
  Wales, 
  and 
  in 
  Ireland. 
  

  

  a. 
  Cambrian 
  Beds 
  of 
  the 
  Caledonian 
  type. 
  N. 
  W. 
  Highlands 
  

   of 
  Scotland. 
  

  

  Sir 
  E. 
  Murchison's 
  description 
  is 
  sufficiently 
  full 
  for 
  my 
  purpose, 
  

   and 
  is 
  as 
  follows 
  : 
  — 
  

  

  "The 
  ancient 
  gneiss, 
  along 
  the 
  coast 
  of 
  Sutherlandshire 
  and 
  

   Eoss, 
  is 
  surmounted 
  by 
  great 
  masses 
  of 
  dull 
  brown, 
  red, 
  and 
  choco- 
  

   late-coloured 
  sandstone 
  and 
  conglomerate" 
  f 
  , 
  generally 
  in 
  nearly 
  

   horizontal 
  courses, 
  rising 
  into 
  the 
  mountains 
  of 
  Coulmore, 
  Suilven, 
  

   Canisp, 
  and 
  Queenaig. 
  The 
  reddish 
  tint 
  is 
  everywhere 
  prevalent 
  ; 
  

   and 
  there 
  is 
  a 
  remarkable 
  absence 
  of 
  beds 
  of 
  slate 
  J 
  ; 
  the 
  deposits 
  

   arc 
  likewise 
  unfossiliferous. 
  

  

  The 
  beds, 
  it 
  will 
  be 
  observed, 
  are 
  not 
  described 
  as 
  ' 
  ; 
  grits," 
  a 
  

   term 
  only 
  applicable 
  to 
  those 
  I 
  am 
  about 
  to 
  describe. 
  

  

  There 
  are 
  no 
  traces 
  of 
  such 
  beds 
  in 
  the 
  north 
  or 
  west 
  of 
  Ireland, 
  

   between 
  the 
  representatives 
  of 
  the 
  Lower 
  Silurian 
  series 
  and 
  those 
  

   of 
  the 
  Laurentian 
  ; 
  I 
  therefore 
  include 
  the 
  north, 
  the 
  west, 
  and 
  the 
  

   centre 
  of 
  Ireland 
  in 
  the 
  Archaean 
  ridge, 
  which 
  was 
  prolonged 
  from 
  the 
  

   central 
  Highlands 
  of 
  Scotland 
  (see 
  Map, 
  fig. 
  1). 
  

  

  b. 
  Cambrian 
  Beds 
  of 
  the 
  Hiber 
  no-Cambrian 
  Type. 
  

  

  For 
  the 
  description 
  of 
  these 
  beds 
  as 
  they 
  occur 
  in 
  the 
  Welsh 
  and 
  

   Salopian 
  area, 
  I 
  adopt 
  the 
  language 
  of 
  Prof. 
  Sir 
  A. 
  Eamsay. 
  " 
  The 
  

   Cambrian 
  rocks 
  of 
  Wales," 
  he 
  says, 
  " 
  consist 
  of 
  the 
  purple 
  grits 
  

   and 
  slates 
  that 
  form 
  the 
  greater 
  part 
  of 
  the 
  group 
  of 
  hills 
  lying- 
  

   east 
  of 
  Cardigan 
  Bay." 
  " 
  They 
  are 
  also 
  well 
  seen 
  in 
  the 
  

  

  passes 
  of 
  Llanberris 
  and 
  1ST 
  ant 
  Ffrancon, 
  where 
  the 
  celebrated 
  slate- 
  

   quarries 
  of 
  Penrhyn 
  and 
  Llanberris 
  lie 
  in 
  these 
  strata. 
  The 
  slates 
  

   are 
  purple, 
  purplish-blue, 
  and 
  green 
  ; 
  and 
  associated 
  with 
  them 
  are 
  

   beds 
  of 
  greenish 
  and 
  grey 
  grits 
  and 
  conglomerates 
  "§. 
  Again, 
  the 
  

   Longmyncl 
  rocks 
  " 
  consist 
  of 
  green, 
  grey, 
  and 
  purple 
  slaty 
  rocks, 
  

   grits, 
  and 
  conglomerates," 
  in 
  which 
  are 
  worm-burrowings, 
  and 
  a 
  

   Trilobite 
  (Palazopyge 
  Bamsayi) 
  discovered 
  by 
  the 
  late 
  Mr. 
  Salter. 
  

  

  * 
  " 
  Archaean 
  Geology 
  of 
  Anglesey," 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  May 
  1881. 
  

  

  t 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  xv. 
  p. 
  362. 
  

  

  % 
  Sir 
  R. 
  Murchison 
  compares 
  these 
  beds 
  to 
  their 
  representatives 
  in 
  the 
  Long- 
  

   mynd 
  hills 
  of 
  Shropshire 
  ; 
  but 
  there 
  is 
  a 
  marked 
  general 
  absence 
  of 
  resemblance 
  

   between 
  the 
  " 
  grey 
  and 
  purplish 
  slaty, 
  gritty, 
  and 
  pebbly 
  rocks" 
  of 
  the 
  Longmynd 
  

   (Phillips) 
  and 
  the 
  reddish 
  sandstones 
  and 
  conglomerates 
  of 
  Ross-shire. 
  

  

  § 
  Phys. 
  Geol. 
  Great 
  Britain, 
  5th 
  edit. 
  p. 
  58. 
  

  

  