﻿436 
  Forty-seventh 
  Report 
  on 
  the 
  State 
  Museum. 
  

  

  escarpment, 
  and 
  is 
  a 
  surface 
  formation 
  over 
  the 
  wide 
  area 
  in 
  

   western 
  Coeymans 
  township 
  drained 
  by 
  Hannecrois 
  creek, 
  

   deeply 
  excavated 
  by 
  the 
  Switzkill, 
  up 
  which 
  it 
  extends 
  southward 
  

   nearly 
  to 
  South 
  Berne, 
  and 
  it 
  occupies 
  a 
  wide 
  area 
  of 
  moderately 
  

   high 
  land 
  extending 
  north 
  from 
  East 
  Berne. 
  It 
  consists 
  in 
  greater 
  

   part 
  of 
  shales, 
  hard 
  above 
  and 
  softer 
  below, 
  with 
  occasional 
  thin, 
  

   intercalated 
  beds 
  of 
  flaggy 
  sandstones 
  among 
  its 
  upper 
  members. 
  

   Its 
  basal 
  beds 
  are 
  in 
  some 
  places 
  so 
  dark 
  that 
  they 
  have 
  been 
  

   mistaken 
  for 
  coal, 
  and 
  many 
  attempts 
  have 
  been 
  made 
  to 
  work 
  

   them 
  for 
  coal. 
  Their 
  dark 
  tint 
  is 
  due 
  to 
  the 
  presence 
  of 
  a 
  very 
  

   large 
  amount 
  of 
  carbonaceous 
  material, 
  which 
  in 
  some 
  cases 
  will 
  

   burn 
  for 
  a 
  few 
  minutes 
  when 
  the 
  shale 
  is 
  put 
  in 
  the 
  fire. 
  There 
  

   are, 
  however, 
  as 
  every 
  geologist 
  knows, 
  no 
  beds 
  of 
  coal 
  in 
  this 
  

   formation, 
  and 
  all 
  attempts 
  to 
  obtain 
  coal 
  therefrom 
  will 
  be 
  

   futile. 
  The 
  shales 
  of 
  this 
  formation 
  are 
  abundantly 
  fossiliferous 
  

   in 
  certain 
  beds 
  at 
  various 
  horizons, 
  and, 
  as 
  well 
  known, 
  contain 
  

   the 
  fauna 
  of 
  the 
  lower 
  Hamilton 
  group. 
  

  

  Onondaga 
  limestone. 
  — 
  This 
  formation 
  gives 
  rise 
  to 
  a 
  terrace 
  

   of 
  greater 
  or 
  less 
  width 
  extending 
  along 
  the 
  foot 
  of 
  the 
  steep 
  

   slopes 
  of 
  the 
  Hamilton 
  shales. 
  In 
  the 
  northeastern 
  face 
  of 
  the 
  

   Helderoerg 
  mountain 
  its 
  outcrop 
  is 
  very 
  narrow, 
  in 
  some 
  places 
  

   not 
  over 
  100 
  feet. 
  Westward, 
  it 
  widens 
  to 
  a 
  mile 
  and 
  a 
  half 
  about 
  

   Thompson's 
  lake, 
  then 
  is 
  contracted 
  again 
  by 
  the 
  northern 
  exten- 
  

   sion 
  of 
  the 
  Hamilton 
  formation 
  north 
  from 
  East 
  Berne, 
  west 
  from 
  

   which 
  it 
  widens 
  to 
  nearly 
  three 
  miles 
  in 
  the 
  long 
  slopes 
  north- 
  

   west 
  of 
  Berne. 
  It 
  is 
  spread 
  out 
  over 
  a 
  considerable 
  width 
  

   about 
  Clarksville 
  and 
  Oniskethau 
  creek. 
  At 
  the 
  north 
  end 
  of 
  

   Copeland 
  and 
  Blodgett 
  hills 
  it 
  is 
  narrowed 
  to 
  200 
  yards, 
  

   constituting 
  a 
  very 
  distinct 
  shelf, 
  on 
  the 
  relatively 
  smooth 
  surface 
  

   of 
  which 
  the 
  road 
  passes 
  for 
  several 
  miles. 
  A 
  mile 
  east 
  of 
  

   Clarksville 
  there 
  is 
  a 
  small 
  outlier 
  of 
  the 
  formation, 
  which 
  is 
  a 
  

   very 
  unusual 
  feature. 
  There 
  is 
  also 
  a 
  small 
  outlying 
  area 
  on 
  top 
  

   of 
  the 
  ridge 
  three 
  miles 
  south 
  by 
  west 
  of 
  South 
  Bethlehem. 
  

  

  The 
  surface 
  of 
  the 
  formation 
  is 
  much 
  obscured 
  by 
  drift 
  in 
  some 
  

   districts, 
  notably 
  in 
  the 
  wide 
  area 
  north 
  of 
  Peoria 
  where 
  outcrops 
  

   are 
  exceedingly 
  rare 
  on 
  this 
  account. 
  

  

  The 
  formation 
  consists 
  of 
  a 
  light 
  blue 
  gray, 
  sub-crystalline, 
  

   tough, 
  massively-bedded, 
  pure 
  limestone 
  containing 
  lenses 
  of 
  

   chert 
  in 
  courses 
  and 
  irregularly 
  disseminated. 
  In 
  the 
  bed 
  of 
  a 
  

  

  