﻿Brigham 
  — 
  Drift 
  Bowlders 
  in 
  Central 
  New 
  York. 
  221 
  

  

  abundant 
  springs 
  issuing 
  on 
  these 
  planes 
  suggest 
  the 
  setting 
  off 
  

   of 
  the 
  blocks 
  by 
  freezing. 
  But 
  some 
  lie 
  in 
  positions 
  in 
  which 
  

   only 
  glacial 
  plucking 
  could 
  have 
  placed 
  them. 
  

  

  the 
  shelf 
  of 
  Lower 
  Helderberg, 
  varying 
  from 
  40 
  to 
  80 
  rods 
  

   in 
  width 
  and 
  sloping 
  gently 
  to 
  the 
  eastward, 
  has 
  been 
  swept 
  

   clear 
  of 
  the 
  overlying 
  Oriskany. 
  Evidently 
  the 
  power 
  to 
  

   pluck 
  ceased 
  more 
  abruptly 
  than 
  the 
  power 
  to 
  transport. 
  But 
  

   the 
  outmost 
  blocks 
  of 
  the 
  ledge 
  were 
  considerably 
  pared 
  off 
  by 
  

   grinding 
  action 
  after 
  their 
  neighbors 
  had 
  been 
  carried 
  away. 
  

   The 
  general 
  movement 
  of 
  the 
  ice 
  was 
  slightly 
  off 
  the 
  ledge 
  to 
  

   the 
  eastward. 
  The 
  lower 
  ice, 
  which 
  accomplished 
  the 
  pluck- 
  

   ing, 
  may 
  have 
  swerved 
  to 
  the 
  east 
  locally 
  on 
  this 
  rather 
  steep 
  

   valley 
  wall, 
  thus 
  increasing 
  the 
  otherwise 
  slight 
  angle 
  between 
  

   the 
  line 
  of 
  movement 
  and 
  the 
  line 
  of 
  the 
  ledge. 
  Doubtless 
  by 
  

   weathering 
  along 
  the 
  joint 
  planes, 
  and 
  by 
  solution 
  of 
  the 
  upper 
  

   surface 
  of 
  the 
  subjacent 
  limestone, 
  as 
  seen 
  under 
  the 
  present 
  

   ledge, 
  the 
  blocks 
  had 
  been 
  loosened 
  and 
  plucking 
  thus 
  facil- 
  

   itated. 
  Even 
  with 
  this 
  assistance 
  it 
  is 
  puzzling 
  to 
  understand 
  

   how 
  blocks 
  of 
  some 
  scores 
  of 
  tons 
  weight 
  could 
  be 
  handled, 
  

   with 
  so 
  little 
  purchase 
  as 
  seems 
  to 
  have 
  been 
  possible.* 
  

  

  The 
  Oriskany 
  valley 
  runs 
  K". 
  60° 
  E. 
  from 
  the 
  divide 
  to 
  

   Oriskany 
  Falls, 
  and 
  thence 
  N. 
  N* 
  E. 
  toward 
  the 
  Mohawk. 
  We 
  

   have 
  here 
  ideal 
  conditions 
  for 
  seeing 
  how 
  ice 
  behaves 
  in 
  cross- 
  

   ing 
  a 
  valley 
  diagonally. 
  Our 
  best 
  data 
  are 
  afforded 
  by 
  the 
  

   transport 
  of 
  large 
  blocks 
  from 
  the 
  above 
  described 
  ledge. 
  The 
  

   striae 
  so 
  far 
  as 
  found, 
  and 
  certain 
  glacial 
  flutings 
  on 
  the 
  hills, 
  

   support 
  the 
  evidence 
  furnished 
  by 
  the 
  travelled 
  blocks. 
  These 
  

   bowlders 
  were 
  noted 
  by 
  Yanuxem 
  :f 
  

  

  " 
  The 
  Oriskany 
  sandstone 
  .first 
  appears 
  out 
  of 
  place 
  and 
  at 
  a 
  

   higher 
  level 
  in 
  Grout's 
  quarry, 
  amongst 
  the 
  drift, 
  or 
  alluvion 
  

   on 
  the 
  top 
  of 
  the 
  Onondaga 
  limestone, 
  the 
  thickness 
  of 
  the 
  

   Cauda-galli 
  Grit 
  and 
  Onondaga 
  Limestone 
  being 
  the 
  difference 
  

   of 
  its 
  original 
  position 
  and 
  the 
  top 
  of 
  the 
  quarry. 
  The 
  sand- 
  

   stone 
  showed 
  characters 
  of 
  a 
  local 
  origin. 
  The 
  same 
  sandstone 
  

   is 
  found 
  in 
  great 
  abundance 
  and 
  immense 
  blocks, 
  scattered 
  

   over 
  the 
  hills 
  in 
  the 
  towns 
  of 
  Madison, 
  Eaton, 
  Hamilton 
  and 
  

   Lebanon, 
  being 
  more 
  numerous 
  toward 
  the 
  valley 
  of 
  the 
  

   Chenango 
  canal. 
  They 
  appear 
  on 
  the 
  side-hills, 
  but 
  few 
  hav- 
  

   ing 
  been 
  noticed 
  toward 
  the 
  middle 
  of 
  the 
  valleys. 
  All 
  the 
  

   blocks 
  there 
  seen 
  were 
  the 
  counterpart 
  of 
  the 
  mass 
  at 
  Oriskany 
  

   Falls, 
  being 
  readily 
  recognized 
  from 
  local 
  differences 
  in 
  the 
  

   rock, 
  prevailing 
  at 
  all 
  its 
  points 
  of 
  outcrop." 
  At 
  page 
  127, 
  

   Yanuxem 
  speaks 
  again 
  of 
  the 
  frequency 
  of 
  the 
  bowlders 
  in 
  

   the 
  towns 
  named 
  and 
  adds, 
  — 
  " 
  In 
  smaller 
  masses 
  it 
  has 
  been 
  

  

  *See 
  however 
  T. 
  C. 
  Chamberlin, 
  Rock 
  Scorings 
  of 
  the 
  great 
  Ice 
  Invasions, 
  

   7th 
  Ann. 
  Rep. 
  U. 
  S. 
  G. 
  S., 
  p. 
  193. 
  

  

  f 
  Geol. 
  3d 
  Distr., 
  N. 
  Y., 
  pp. 
  127, 
  222-223. 
  

  

  