﻿580 
  JBORTY-SEVENTH 
  REPORT 
  ON 
  THE 
  8 
  TATE 
  MUSEUM. 
  

  

  is 
  pink, 
  reddish-brown 
  or 
  greenish 
  gray 
  ; 
  second, 
  the 
  North 
  river 
  

   stone 
  is 
  almost 
  wholly 
  a 
  fine 
  grained, 
  silicious 
  sandstone, 
  with 
  

   very 
  little 
  argillaceous 
  matter 
  ; 
  the 
  Catskill 
  stone 
  has 
  more 
  clay 
  t 
  y 
  

   matter, 
  and 
  is 
  not 
  so 
  compact; 
  third, 
  the 
  North 
  river 
  stone 
  is 
  of 
  

   a 
  very 
  uniform 
  tint 
  and 
  texture, 
  while 
  the 
  Catskill 
  stone 
  varies 
  

   between 
  the 
  shades 
  given 
  above, 
  and 
  is 
  not 
  as 
  apt 
  to 
  be 
  constant 
  

   in 
  its 
  characteristics. 
  

  

  These 
  points 
  of 
  difference, 
  together 
  with 
  the 
  distinct 
  change 
  

   with 
  change 
  of 
  elevation, 
  appears 
  to 
  make 
  it 
  quite 
  certain 
  that 
  

   these 
  flagstones 
  belong 
  to 
  two 
  distinct 
  geologic 
  horizons. 
  Prof. 
  

   Smock, 
  " 
  Building 
  Stones 
  of 
  New 
  York," 
  p. 
  266, 
  regards 
  all 
  of 
  

   the 
  quarries 
  above 
  Boiceville 
  as 
  in 
  the 
  Catskill 
  group 
  of 
  rocks. 
  

  

  In 
  each 
  of 
  these 
  groups 
  the 
  workable 
  stone 
  appears 
  under 
  about 
  

   the 
  same 
  conditions. 
  The 
  whole 
  formation 
  consists 
  broadly 
  of 
  

   shales 
  and 
  thin-bedded 
  (flagstone) 
  layers 
  and 
  thick-bedded 
  layers 
  

   of 
  sandstone. 
  In 
  any 
  one 
  group, 
  as 
  for 
  instance 
  the 
  Hamilton, 
  

   there 
  are 
  several 
  alternating 
  layers 
  or 
  beds 
  of 
  worthless 
  shale 
  and 
  

   beds 
  of 
  workable 
  stone. 
  The 
  shales 
  consist 
  of 
  very 
  thin 
  argilla- 
  

   ceous 
  and 
  samty 
  layers 
  (the 
  clayey 
  material 
  coming 
  in 
  lenses 
  

   called 
  callous 
  by 
  the 
  quarry 
  men). 
  The 
  beds 
  of 
  workable 
  sand- 
  

   stone 
  vary 
  in 
  thickness 
  from 
  one 
  inch 
  to 
  two 
  feet. 
  The 
  total 
  

   thickness 
  of 
  the 
  workable 
  beds 
  varies 
  from 
  four 
  inches 
  to 
  eighteen 
  

   feet. 
  The 
  thickness 
  of 
  the 
  shaly 
  or 
  slaty 
  beds 
  between 
  the 
  work- 
  

   able 
  beds 
  is 
  unknown, 
  for 
  it 
  is 
  not 
  possible 
  to 
  work 
  a 
  given 
  bed 
  

   at 
  a 
  profit, 
  if 
  the 
  stripping 
  required 
  exceeds 
  eight 
  to 
  fifteen 
  feet 
  

   maximum. 
  If 
  the 
  side 
  hill 
  or 
  outcrop 
  in 
  which 
  the 
  workable 
  bed 
  

   occurs 
  is 
  very 
  steep 
  the 
  bed 
  can 
  be 
  uncovered 
  a 
  distance 
  of 
  from 
  

   twenty 
  five 
  to 
  one 
  hundred 
  feet, 
  more 
  or 
  less, 
  before 
  the 
  thickness 
  

   of 
  the 
  overlying 
  slate 
  becomes 
  too 
  great 
  to 
  be 
  removed 
  at 
  a 
  profit. 
  

  

  The 
  entire 
  formation 
  dips 
  at 
  varying 
  but 
  usually 
  genile 
  angles 
  

   to 
  the 
  northwest. 
  The 
  quarry 
  faces 
  are 
  thus 
  turned 
  to 
  the 
  east. 
  

   The 
  quarries 
  have 
  the 
  appearance 
  of 
  being 
  located 
  along 
  the 
  

   eastern 
  edge 
  of 
  a 
  monoclinal 
  outcrop. 
  In 
  places 
  there 
  are 
  two 
  or 
  

   three 
  series 
  of 
  quarries 
  parallel 
  to 
  each 
  other. 
  It 
  is 
  not 
  certain 
  

   whether 
  this 
  appearance 
  is 
  due 
  to 
  a 
  true 
  monoclinal 
  structure, 
  or 
  

   whether 
  the 
  rocks 
  as 
  a 
  whole 
  have 
  been 
  tilted 
  to 
  the 
  north- 
  

   west. 
  The 
  accompanying 
  cuts 
  show 
  the 
  two 
  possible 
  inter- 
  

   pretations 
  of 
  the 
  structure. 
  Kepetition 
  by 
  faulting 
  appears, 
  

   however, 
  to 
  be 
  the 
  most 
  plausible 
  explanation, 
  though 
  there 
  are 
  

  

  