﻿120 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  The 
  cracks 
  which 
  ramify 
  everywhere 
  through 
  the 
  lava 
  are, 
  for 
  

   the 
  most 
  part, 
  solidly 
  filled 
  with 
  secondary 
  calcite. 
  The 
  amygdules 
  

   are 
  chiefly 
  of 
  this 
  mineral 
  also. 
  

  

  Woodworth 
  described 
  coarser 
  grained 
  rock, 
  containing 
  feldspar 
  

   crystals 
  visible 
  to 
  the 
  eye, 
  from 
  the 
  south 
  end 
  of 
  the 
  knob, 
  and 
  

   the 
  correctness 
  of 
  the 
  description 
  was 
  verified 
  by 
  Cushing's 
  study 
  

   of 
  the 
  thin 
  section. 
  But 
  we 
  have 
  been 
  unable 
  to 
  find 
  any 
  rock 
  of 
  

   this 
  type 
  in 
  our 
  later 
  work. 
  Some 
  rock 
  has 
  been 
  removed 
  from 
  

   the 
  south 
  end 
  though 
  the 
  original 
  thickness 
  was 
  but 
  slight. 
  None 
  

   of 
  this 
  coarser 
  material 
  remains 
  and 
  we 
  are 
  left 
  in 
  entire 
  uncer- 
  

   tainty 
  as 
  to 
  its 
  original 
  amount. 
  

  

  Fig. 
  II 
  Natural 
  size 
  drawing 
  of 
  a 
  hand 
  specimen 
  of 
  corroded 
  limestone 
  in 
  

  

  pitchstone 
  

  

  The 
  inclusions. 
  Inclusions 
  abound 
  throughout 
  the 
  plug, 
  both 
  in 
  

   the 
  lava 
  balls 
  and 
  in 
  the 
  intervening 
  material. 
  They 
  are 
  all 
  of 
  lime- 
  

   stone, 
  and 
  limestone 
  of 
  but 
  a 
  single 
  type. 
  Though 
  the 
  knob 
  stands 
  

   surrounded 
  by 
  black 
  shales, 
  there 
  are 
  no 
  shale 
  inclusions 
  in 
  it. 
  It 
  

   is 
  possible 
  that 
  there 
  may 
  be 
  inclusions 
  of 
  earlier 
  trap, 
  and 
  the 
  

   coarser 
  grained 
  rock 
  just 
  mentioned 
  may 
  be 
  an 
  inclusion. 
  But 
  on 
  

   this 
  point 
  we 
  have 
  no 
  certain 
  evidence. 
  

  

  The 
  inclusions 
  are 
  of 
  pure 
  limestone, 
  effervescing 
  briskly 
  and 
  

   immediately 
  with 
  acid. 
  They 
  range 
  in 
  size 
  up 
  to 
  masses 
  a 
  foot 
  

  

  