﻿geologic 
  formations 
  of 
  new 
  york 
  163 
  

  

  Hamilton 
  Shale 
  

  

  The 
  Marcellus 
  shales 
  change 
  gradually 
  at 
  their 
  higher 
  part 
  

   into 
  the 
  Hamilton 
  shale 
  which 
  is 
  a 
  harder, 
  lighter 
  colored 
  mass, 
  

   often 
  containing 
  sandstones, 
  and, 
  in 
  central 
  New 
  York 
  and 
  as 
  

   far 
  east 
  as 
  the 
  Catskill 
  range, 
  is 
  1,000 
  feet 
  or 
  more 
  in 
  thickness. 
  

   Like 
  the 
  Marcellus 
  shale, 
  many 
  parts 
  of 
  it 
  show 
  few 
  marks 
  of 
  

   stratification; 
  but 
  it 
  is 
  divided 
  vertically 
  by 
  joints, 
  which, 
  

   where 
  it 
  is 
  excavated, 
  are 
  often 
  as 
  upright 
  and 
  smooth 
  as 
  the 
  

   walls 
  of 
  a 
  plastered 
  building. 
  In 
  the 
  more 
  eastern 
  part 
  

   of 
  the 
  state, 
  it 
  is 
  generally 
  coarse-grained 
  and 
  sandy; 
  in 
  western 
  

   New 
  York, 
  it 
  is 
  fine-grained, 
  soft 
  and 
  more 
  calcareous, 
  forming 
  

   by 
  its 
  decomposition 
  a 
  rich 
  soil. 
  

  

  In 
  the 
  survey 
  of 
  the 
  fourth 
  district 
  Hall 
  divided 
  the 
  Hamilton 
  

   into 
  three 
  parts; 
  at 
  the 
  base 
  the 
  Ludloicville 
  shale, 
  overlaid 
  by 
  the 
  

   Encrinal 
  limestone 
  and 
  at 
  the 
  summit 
  the 
  Moscow 
  shale. 
  The 
  

   Ludlowville 
  and 
  Moscow 
  horizons 
  take 
  their 
  name 
  from 
  localities 
  

   in 
  western 
  New 
  York. 
  The 
  Encrinal 
  limestone 
  is 
  named 
  from 
  its 
  

   prevailing 
  ' 
  fossil. 
  

  

  Tully 
  limestone 
  

  

  The 
  Hamilton 
  group 
  terminates 
  in 
  central 
  New 
  York 
  with 
  a 
  

   very 
  impure 
  dark 
  limestone, 
  about 
  10 
  feet 
  thick, 
  which 
  received 
  

   its 
  name 
  from 
  the 
  village 
  of 
  Tully 
  in 
  Onondaga 
  county. 
  In 
  the 
  

   eastern 
  and 
  western 
  parts 
  of 
  the 
  state 
  this 
  rock 
  does 
  not 
  exist, 
  

   as 
  it 
  extends 
  only 
  from 
  Ontario 
  county 
  to 
  Madison, 
  and 
  beyond 
  

   these 
  limits 
  the 
  Genesee 
  slate 
  lies 
  directly 
  on 
  the 
  Hamilton 
  group. 
  

   The 
  Tully 
  limestone 
  contains 
  some 
  fossils 
  which 
  are 
  common 
  to 
  

   it 
  and 
  the 
  lower 
  shales. 
  

  

  Genesee 
  

  

  The 
  next 
  rock 
  in 
  upward 
  order 
  is 
  the 
  Genesee, 
  a 
  series 
  of 
  layers 
  

   of 
  thin-bedded, 
  fissile, 
  black 
  slate, 
  in 
  some 
  places 
  150 
  feet 
  thick, 
  

   but 
  diminishing 
  westward 
  so 
  that 
  it 
  is 
  only 
  about 
  25 
  feet 
  on 
  

   Lake 
  Erie. 
  It 
  is, 
  however, 
  distinctly 
  recognized 
  in 
  Pennsylvania, 
  

   where 
  it 
  is 
  some 
  300 
  feet 
  thick. 
  It 
  derives 
  its 
  name 
  from 
  one 
  of 
  

   its 
  best 
  localities 
  in 
  this 
  state, 
  the 
  gorge 
  of 
  the 
  Genesee 
  river 
  

  

  