﻿340 
  PROCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  [Apr. 
  27, 
  

  

  on 
  either 
  side 
  of 
  Arisaig 
  Brook 
  lofty 
  exposures 
  of 
  shale, 
  with 
  cha- 
  

   racteristic 
  fossils 
  of 
  B'. 
  Succeeding 
  them 
  are 
  seen 
  slate-rocks, 
  

   forming 
  hills 
  of 
  still 
  greater 
  elevation, 
  on 
  the 
  summit 
  of 
  the 
  highest 
  

   of 
  which 
  is 
  an 
  outcrop 
  of 
  these 
  strata, 
  where 
  I 
  found 
  in 
  situ 
  the 
  

   largest 
  Lingula 
  that 
  I 
  have 
  yet 
  seen, 
  and 
  abundance 
  of 
  fragments 
  

   of 
  stems 
  of 
  Crinoids. 
  I 
  consider 
  this 
  to 
  be 
  the 
  beginning 
  of 
  the 
  

   eqiuvalent 
  of 
  the 
  Aymestry 
  limestone 
  (Salter), 
  or 
  the 
  C 
  member 
  of 
  

   our 
  series. 
  There 
  is 
  an 
  interesting 
  bed 
  of 
  this 
  group 
  exposed 
  on 
  

   the 
  side 
  of 
  the 
  brook 
  ; 
  it 
  is 
  very 
  ferruginous, 
  almost 
  constituting 
  an 
  

   ore 
  of 
  iron 
  ; 
  it 
  is 
  from 
  six 
  to 
  nine 
  inches 
  thick, 
  and 
  replete 
  with 
  casts 
  

   of 
  Strophomena 
  (various 
  species), 
  Athi/ris 
  tumida 
  1 
  ?, 
  Homalonotus, 
  

   Cornulites, 
  &c. 
  We 
  now 
  evidently 
  approach 
  the 
  synclinal 
  axis, 
  as 
  

   the 
  strata 
  exposed 
  on 
  the 
  sides 
  of 
  the 
  brook 
  become 
  distorted. 
  A 
  

   valley 
  which 
  extends 
  from 
  this 
  part 
  in 
  a 
  westerly 
  direction 
  appears 
  

   to 
  correspond 
  with 
  this 
  axis. 
  The 
  ground 
  through 
  which 
  our 
  section 
  

   now 
  passes 
  becomes 
  removed 
  from 
  the 
  brook; 
  it 
  begins 
  to 
  rise 
  with- 
  

   out 
  exhibiting 
  an 
  outcrop 
  of 
  any 
  importance 
  until 
  we 
  reach 
  the 
  

   summit 
  of 
  a 
  hill 
  still 
  higher 
  than 
  any 
  through 
  which 
  the 
  section 
  has 
  

   passed, 
  and 
  the 
  highest 
  formed 
  by 
  the 
  Silurian 
  strata. 
  The 
  strata 
  

   outcropping 
  on 
  the 
  top, 
  and 
  towards 
  it, 
  belong 
  to 
  the 
  group 
  D, 
  or 
  

   the 
  Ludlow 
  Tilestone 
  (Salter), 
  and 
  are 
  inclined 
  at 
  a 
  low 
  angle 
  and 
  

   with 
  a 
  northerly 
  dip. 
  Here 
  I 
  found 
  in 
  situ 
  characteristic 
  species 
  of 
  

   this 
  member, 
  namely, 
  Dalmania 
  Logani, 
  Hall 
  ; 
  Phacops 
  Downingice, 
  

   Salt. 
  ; 
  Homalonotus 
  Dawsoni, 
  Hall; 
  H.Knightii, 
  Salt.; 
  Beyrichia, 
  sp.; 
  

   Crania 
  Acadiensis, 
  Hall. 
  The 
  rocks 
  which 
  doubtless 
  underlie 
  the 
  

   above 
  do 
  not 
  appear 
  in 
  any 
  way 
  on 
  the 
  hill- 
  side 
  or 
  in 
  the 
  valley, 
  

   and 
  there 
  is 
  no 
  trace 
  whatever 
  of 
  the 
  old 
  anticlinal 
  ; 
  we 
  have 
  trap 
  

   (a') 
  at 
  a 
  considerable 
  distance 
  up 
  Doctor's 
  Brook, 
  at 
  the 
  extreme 
  of 
  

   our 
  section, 
  succeeded 
  by 
  syenite. 
  

  

  § 
  5. 
  Section 
  from 
  the 
  Frenchman's 
  Barn 
  to 
  M'Cara's 
  Brook. 
  

  

  This 
  section 
  (fig. 
  4) 
  passes 
  through 
  all 
  the 
  members 
  of 
  the 
  north 
  

   side 
  of 
  the 
  synclinal 
  in 
  an 
  oblique 
  direction, 
  its 
  course 
  being 
  from 
  

   N.N.E. 
  to 
  S.S.W., 
  corresponding 
  generally 
  with 
  the 
  section 
  on 
  the 
  

   shore. 
  It 
  commences 
  with 
  what 
  is 
  known 
  locally, 
  and 
  from 
  maps 
  of 
  

   Nova 
  Scotia, 
  as 
  the 
  Frenchman's 
  Barn, 
  on 
  the 
  N.N.E., 
  and 
  termi- 
  

   nates 
  at 
  M'Cara's 
  Brook, 
  or 
  about 
  -J-th 
  of 
  a 
  mile 
  beyond 
  what 
  I 
  at 
  

   present 
  consider 
  as 
  the 
  termination 
  of 
  the 
  group. 
  This 
  is 
  the 
  most 
  

   interesting 
  of 
  the 
  three 
  sections, 
  as 
  it 
  includes 
  the 
  chief 
  sphere 
  of 
  

   Dr. 
  Dawson's 
  researches 
  and 
  of 
  my 
  own. 
  Prom 
  localities 
  embraced 
  

   in 
  this 
  line 
  of 
  section 
  the 
  fossils 
  have 
  been 
  derived 
  which 
  have 
  

   enabled 
  us 
  to 
  solve 
  the 
  problem 
  of 
  its 
  relative 
  age. 
  

  

  The 
  Frenchman's 
  Barn 
  is 
  a 
  lofty 
  oblong 
  mass 
  of 
  jaspideous 
  rock, 
  

   with 
  a 
  broad 
  and 
  somewhat 
  fiat 
  summit. 
  North 
  of 
  this, 
  trap 
  is 
  

   visible. 
  On 
  either 
  side, 
  similarly 
  altered 
  strata 
  (A) 
  are 
  seen 
  rising 
  

   in 
  bold 
  and 
  striking 
  masses. 
  Large 
  and 
  numerous 
  blocks 
  of 
  these 
  

   rocks 
  are 
  scattered 
  on 
  the 
  surface. 
  Sometimes 
  they 
  are 
  transported 
  

   to 
  a 
  considerable 
  distance 
  to 
  the 
  south, 
  the 
  whole 
  deceiving 
  the 
  

   cursory 
  observer 
  into 
  the 
  belief 
  that 
  they 
  are 
  derived 
  from 
  the 
  

   underlying 
  rocks 
  ; 
  but 
  an 
  examination 
  of 
  adjoining 
  brooks, 
  as 
  well 
  

   as 
  of 
  outcrops, 
  shows 
  that 
  the 
  underlying 
  strata 
  include 
  B 
  and 
  B' 
  of 
  

  

  