﻿90 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  dermining 
  of 
  the 
  upper 
  layers 
  thus 
  results 
  in 
  their 
  ultimate 
  breaking 
  

   down 
  from 
  non-support, 
  and 
  the 
  resulting 
  fall 
  of 
  rocks 
  may 
  be 
  of 
  

   a 
  dangerous 
  character. 
  Care 
  is 
  therefore 
  necessary 
  in 
  the 
  examina- 
  

   tion 
  of 
  these 
  sections, 
  and 
  the 
  warnings 
  of 
  the 
  section 
  guards 
  should 
  

   always 
  be 
  heeded. 
  These 
  men 
  patrol 
  the 
  tracks 
  continually 
  from 
  

   early 
  morning 
  till 
  after 
  the 
  last 
  train 
  has 
  passed 
  at 
  night. 
  This 
  is 
  

   necessary, 
  as 
  the 
  fall 
  of 
  rocks 
  is 
  continuous, 
  and 
  often 
  of 
  such 
  

   amount 
  as 
  to 
  obstruct 
  trafhc 
  for 
  some 
  time. 
  Any 
  one 
  who 
  will 
  

   watch 
  these 
  cliiTs 
  for 
  a 
  time 
  from 
  one 
  of 
  the 
  projecting 
  points 
  where 
  

   a 
  comprehensive 
  view 
  may 
  be 
  obtained, 
  and 
  note 
  the 
  almost 
  in- 
  

   cessant 
  fall 
  of 
  rock 
  particles, 
  will 
  receive 
  an 
  impressive 
  object 
  lesson 
  

   in 
  the 
  processes 
  by 
  which 
  clifif 
  retreat 
  is 
  effected. 
  

  

  In 
  many 
  cases 
  the 
  shale 
  banks 
  are 
  covered 
  with 
  a 
  coating 
  of 
  red 
  

   mud 
  carried 
  by 
  rains 
  from 
  the 
  red 
  soil 
  above 
  them. 
  This 
  creates 
  

   the 
  impression 
  that 
  the 
  color 
  of 
  these 
  lower 
  shales 
  is 
  red 
  like 
  that 
  

   of 
  the 
  shales 
  higher 
  up 
  in 
  the 
  series, 
  and 
  only 
  after 
  breaking 
  off 
  

   fresh 
  particles 
  can 
  the 
  true 
  color 
  be 
  seen. 
  

  

  2 
  These 
  gray 
  shales 
  are 
  succeeded 
  by 
  sandstones 
  and 
  sandy 
  

   shales, 
  some 
  of 
  the 
  former 
  massive, 
  quartzose 
  and 
  in 
  beds 
  6 
  or 
  7 
  

   inches 
  in 
  thickness, 
  separated 
  by 
  shaly 
  layers. 
  The 
  sandstone 
  is 
  

   gray 
  and 
  often 
  porous, 
  as 
  if 
  it 
  had 
  undergone 
  some 
  internal 
  solu- 
  

   tion, 
  which 
  suggests 
  that 
  fossils 
  may 
  have 
  been 
  present 
  which 
  were 
  

   dissolved 
  by 
  percolating 
  waters. 
  Fragments 
  of 
  fossils 
  are 
  occasion- 
  

   ally 
  found, 
  but 
  mostly 
  in 
  an 
  unidentifiable 
  condition. 
  Many 
  of 
  the 
  

   thinner 
  and 
  more 
  clayey 
  beds 
  have 
  raised 
  markings 
  on 
  their 
  under 
  

   side, 
  which 
  may 
  be 
  indicative 
  of 
  the 
  former 
  presence 
  of 
  seaweeds 
  in 
  

   the 
  muddy 
  beds 
  of 
  this 
  period. 
  Small 
  black 
  phosphatic 
  pebbles,, 
  

   often 
  very 
  smooth, 
  are 
  not 
  uncommon 
  in 
  some 
  of 
  the 
  layers, 
  and 
  

   larger 
  masses 
  of 
  black, 
  apparently 
  carbonaceous 
  shale 
  are 
  occasion- 
  

   ally 
  found 
  mixed 
  with 
  the 
  sand. 
  In 
  the 
  gray 
  shaly 
  sandstone 
  beds 
  

   the 
  Medina 
  gastropods 
  and 
  bivalves 
  (pelecypods) 
  occur 
  sparingly^ 
  

   and 
  usually 
  in 
  a 
  poor 
  state 
  of 
  preservation. 
  Some 
  of 
  the 
  thin 
  layers 
  

   are 
  calcareous, 
  though 
  still 
  containing 
  a 
  large 
  proportion 
  of 
  argil- 
  

   laceous 
  matter. 
  These 
  are 
  generally 
  fossiliferous, 
  the 
  most 
  common 
  

   organism 
  being 
  a 
  small 
  cylindric 
  bryozoan.^ 
  Fragments 
  of 
  these 
  

  

  ^ 
  Identified 
  provisionally 
  as 
  Helopora 
  fragilis 
  (fig. 
  74). 
  

  

  