﻿the 
  Pennsylvania*)! 
  Strata 
  of 
  Kansas. 
  377 
  

  

  Chamberlin 
  and 
  Salisbury, 
  in 
  a 
  general 
  statement 
  of 
  the 
  sub- 
  

   Aftonian 
  drift, 
  describe 
  it 
  as 
  " 
  typical 
  sheet 
  of 
  till 
  notable 
  for 
  

   the 
  relatively 
  high 
  percentage 
  of 
  its 
  greenstone 
  erratics."* 
  

  

  It 
  is 
  significant 
  that 
  while 
  greenstone 
  and 
  vein 
  quartz 
  

   pebbles 
  and 
  bowlders 
  are 
  very 
  prominent 
  among 
  those 
  of 
  the 
  

   sub-Af 
  tonian 
  drift, 
  not 
  a 
  single 
  greenstone 
  or 
  vein 
  quartz 
  pebble 
  

   or 
  bowlder 
  occurs 
  among 
  the 
  many 
  observed 
  in 
  the 
  locality 
  

   under 
  consideration, 
  and 
  if 
  the 
  material 
  of 
  the 
  latter 
  were 
  

   related 
  in 
  time 
  and 
  origin 
  to 
  the 
  bowlders 
  of 
  the 
  sub-Aftonian 
  

   drift 
  there 
  should 
  be 
  present 
  some 
  material 
  of 
  the 
  character 
  

   typical 
  of 
  that 
  drift. 
  The 
  greenstones 
  might 
  have 
  decayed, 
  

   but 
  the 
  vein 
  quartzes 
  should 
  certainly 
  have 
  outlasted 
  the 
  

   granites. 
  Furthermore, 
  so 
  far 
  as 
  published 
  descriptions 
  

   observed 
  by 
  the 
  writer 
  are 
  concerned, 
  not 
  a 
  single 
  one 
  of 
  the 
  

   sub-Aftonian 
  bowlders 
  is 
  anyways 
  nearly 
  so 
  large 
  as 
  the 
  large 
  

   bowlders 
  of 
  the 
  Rose 
  region. 
  There 
  is 
  no 
  Tertiary 
  material 
  

   on 
  the 
  western 
  plains 
  with 
  which 
  the 
  Hose 
  bowlders 
  can 
  be 
  

   compared, 
  nor 
  is 
  there 
  any 
  evidence 
  that 
  such 
  was 
  ever 
  present. 
  

  

  It 
  is 
  therefore 
  considered 
  that 
  the 
  hypothesis 
  that 
  the 
  bowl- 
  

   ders 
  are 
  of 
  early 
  Pleistocene 
  or 
  Tertiary 
  age 
  is 
  not 
  in 
  harmony 
  

   with 
  the 
  available 
  facts, 
  and 
  while 
  it 
  still 
  must 
  be 
  considered 
  

   as 
  a 
  possibility, 
  it 
  does 
  not 
  appear 
  that 
  it 
  can 
  be 
  strongly 
  main- 
  

   tained. 
  

  

  The 
  chief 
  evidence 
  for 
  the 
  second 
  view 
  is 
  the 
  close 
  corre- 
  

   spondence 
  between 
  the 
  outcrop 
  of 
  the 
  shales 
  and 
  the 
  distribu- 
  

   tion 
  of 
  the 
  large 
  bowlders. 
  As 
  already 
  noted, 
  the 
  large 
  

   bowlders 
  occur 
  on 
  the 
  surface 
  following 
  the 
  outcrop 
  of 
  a 
  

   definite 
  and 
  relatively 
  narrow 
  horizon 
  in 
  the 
  shales. 
  Also 
  

   along 
  the 
  north-south 
  road 
  decayed 
  bowlders 
  are 
  present 
  which 
  

   lie 
  almost 
  surrounded 
  by 
  decayed 
  shales. 
  Residual 
  soil 
  is 
  not 
  

   meant 
  when 
  delayed 
  shales 
  are 
  referred 
  to, 
  but 
  shales 
  in 
  which 
  

   the 
  bedding 
  has 
  not 
  been 
  entirely 
  obliterated. 
  Furthermore, 
  

   in 
  every 
  instance 
  where 
  a 
  bowlder 
  was 
  observed 
  in 
  undisturbed 
  

   position 
  it 
  rested 
  on 
  shales 
  without 
  an 
  intervening 
  soil. 
  In 
  no 
  

   instance, 
  however, 
  were 
  shales 
  seen 
  overlying 
  bowlders. 
  Could 
  

   this 
  observation 
  have 
  been 
  made, 
  it 
  would, 
  of 
  course, 
  have 
  

   definitely 
  decided 
  the 
  problem 
  ; 
  but 
  it 
  was 
  not 
  observed 
  and 
  

   probably 
  never 
  will 
  be 
  since 
  the 
  bowlders 
  are 
  local 
  and 
  the 
  

   cover, 
  if 
  once 
  present, 
  in 
  the 
  immediate 
  vicinity 
  has 
  been 
  

   totally 
  removed. 
  Higher 
  shales 
  are 
  present 
  on 
  the 
  hill, 
  but 
  

   they 
  are 
  a 
  little 
  farther 
  so 
  nth. 
  

  

  If 
  the 
  bowlders 
  are 
  in 
  the 
  shales, 
  the 
  explanation 
  of 
  how 
  

   they 
  reached 
  their 
  present 
  positions 
  is 
  quite 
  simple. 
  The 
  Le- 
  

   Roy 
  shales 
  have 
  been 
  stated 
  to 
  be 
  deltaic 
  in 
  origin, 
  and 
  in 
  strata 
  

   a 
  little 
  above 
  the 
  horizon 
  of 
  the 
  bowlders 
  there 
  is 
  decisive 
  

   evidence 
  of 
  deposition 
  in 
  tumultuous 
  non-marine 
  waters. 
  This 
  

  

  * 
  Chamberlin 
  and 
  Salisbury, 
  Geology, 
  vol. 
  iii, 
  p. 
  384, 
  1907. 
  

  

  