﻿Crosby 
  — 
  Geology 
  of 
  Newport 
  Neck 
  and 
  Conanicut 
  Is. 
  233 
  

  

  Sheep 
  Point 
  to 
  Coggesb 
  all's 
  ledge 
  we 
  pass 
  from 
  the 
  nieta- 
  

   morphic 
  slate 
  to 
  the 
  granite. 
  The 
  contact 
  is 
  beautifully 
  

   exposed 
  and 
  typically 
  igneous, 
  the 
  granite 
  being 
  clearly 
  the 
  

   newer 
  rock. 
  The 
  granite 
  is 
  bordered 
  by 
  a 
  felsitic 
  or 
  micro- 
  

   crystalline 
  layer 
  four 
  to 
  six 
  inches 
  wide 
  penetrating 
  the 
  slate 
  

   very 
  irregularly, 
  and 
  forming 
  numerous 
  dikes 
  six 
  inches 
  to 
  

   three 
  feet 
  wide. 
  The 
  two 
  rocks 
  are 
  firmly 
  welded 
  together. 
  

   Following 
  the 
  granite 
  around 
  the 
  shore 
  to 
  Bailey's 
  Beach, 
  we 
  

   come 
  again, 
  at 
  the 
  east 
  end 
  of 
  the 
  beach, 
  upon 
  the 
  metamorphic 
  

   slate 
  ; 
  but 
  the 
  contact 
  is 
  not 
  exposed, 
  what 
  Dale 
  has 
  described 
  

   as 
  a 
  contact 
  being, 
  apparently, 
  a 
  dike 
  of 
  greenish 
  slaty 
  trap 
  in 
  

   the 
  granite. 
  The 
  north-south 
  strike 
  and 
  high 
  dips 
  of 
  the 
  unal- 
  

   tered 
  Carboniferous 
  strata 
  north 
  of 
  Sheep 
  Point 
  suggest 
  a 
  

   northeast-southwest 
  fault 
  between 
  the 
  older 
  and 
  newer 
  slates 
  

   almost 
  as 
  plainly 
  as 
  on 
  Newport 
  Neck. 
  

  

  On 
  Conanicut 
  Island 
  the 
  metamorphism 
  of 
  the 
  ancient 
  slate 
  

   series 
  is 
  more 
  marked 
  near 
  the 
  granite, 
  and 
  there 
  is 
  a 
  more 
  dis- 
  

   tinct 
  gradation 
  in 
  metamorphic 
  character, 
  than 
  on 
  Newport 
  

   Neck. 
  We 
  pass 
  from 
  the 
  granite 
  to 
  a 
  massive 
  semicrystalline 
  

   greenish 
  rock, 
  almost 
  destitute 
  of 
  recognizable 
  bedding 
  lines 
  

   and 
  netted 
  with 
  veinlets 
  of 
  quartz 
  and 
  epidote. 
  This 
  grades 
  

   into 
  the 
  normal 
  flinty 
  slate 
  similar 
  to 
  that 
  of 
  Newport 
  Neck, 
  

   which 
  is 
  in 
  part 
  distinctly 
  bedded, 
  with 
  approximately 
  east- 
  

   west 
  strike 
  and 
  vertical 
  dip. 
  Pirsson 
  states 
  that 
  " 
  every 
  transi- 
  

   tion 
  can 
  be 
  found 
  between 
  unaltered 
  shales 
  and 
  the 
  most 
  solid 
  

   of 
  hornstones 
  in 
  contact 
  with 
  the 
  granite, 
  but 
  not, 
  however, 
  in 
  

   any 
  one 
  place 
  or 
  exposure." 
  I 
  find, 
  on 
  the 
  contrary, 
  that, 
  so 
  

   far 
  as 
  the 
  shales 
  are 
  concerned, 
  they 
  show 
  absolutely 
  no 
  grada- 
  

   tion 
  in 
  the 
  degree 
  of 
  metamorphism 
  along 
  lines 
  normal 
  to 
  the 
  

   border 
  of 
  the 
  granite 
  ; 
  and 
  the 
  metamorphism 
  is 
  quite 
  as 
  

   marked 
  miles 
  away 
  from 
  the 
  -granite 
  as 
  in 
  its 
  vicinity. 
  The 
  

   drift 
  mantle 
  north 
  of 
  the 
  granite 
  and 
  metamorphic 
  slate 
  is 
  

   practically 
  continuous 
  from 
  shore 
  to 
  shore 
  ; 
  and 
  Pirsson 
  is 
  able 
  

   to 
  point 
  out 
  only 
  one 
  exposure 
  where 
  the 
  supposed 
  gradation 
  

   of 
  the 
  shales 
  into 
  the 
  typical 
  flinty 
  slate 
  or 
  hornstone 
  can 
  be 
  

   observed. 
  He 
  says 
  : 
  " 
  In 
  the 
  northeast 
  (printed 
  northwest) 
  

   corner 
  of 
  D 
  5 
  (figure 
  2) 
  just 
  south 
  of 
  Mr. 
  Green's 
  barn 
  occurs 
  

   a 
  long 
  outcrop 
  extending 
  toward 
  the 
  south. 
  At 
  the 
  north 
  end 
  

   the 
  shales, 
  although 
  still 
  retaining 
  a 
  fissile 
  character, 
  are 
  very 
  

   much 
  gnarled 
  and 
  toughened, 
  and 
  as 
  one 
  proceeds 
  southward 
  

   they 
  pass 
  within 
  two 
  or 
  three 
  rods 
  into 
  compact 
  hornstones. 
  

   From 
  this 
  exposure 
  it 
  may 
  be 
  seen 
  that 
  the 
  loss 
  of 
  the 
  shaly 
  

   character 
  and 
  transition 
  into 
  hornstone 
  occurs 
  within 
  a 
  very 
  

   short 
  distance." 
  I 
  have 
  closely 
  scrutinized 
  this 
  outcrop 
  ; 
  but 
  

   find 
  myself 
  unable 
  to 
  accept 
  Pirsson's 
  interpretation 
  of 
  it. 
  It 
  

   seems 
  to 
  me 
  to 
  belong 
  wholly 
  to 
  the 
  flinty 
  slate, 
  the 
  supposed 
  

   gradation 
  being 
  simply 
  one 
  of 
  the 
  many 
  local 
  variations 
  of 
  this 
  

   formation. 
  But 
  even 
  in 
  this 
  sense 
  I 
  can 
  see 
  no 
  real 
  gradation. 
  

  

  