﻿180 
  E. 
  H. 
  Williams 
  — 
  Southern 
  Ice 
  Limit 
  in 
  Pennsylvania. 
  

  

  with 
  glacial 
  trash. 
  Much 
  discussion 
  has 
  been 
  held 
  regarding 
  

   the 
  Berwick 
  gravels, 
  and 
  some 
  have 
  held 
  that 
  they 
  were 
  due 
  to 
  

   a 
  submerged 
  mouth 
  of 
  the 
  river. 
  As 
  the 
  ice 
  went 
  25-30 
  miles 
  

   south 
  of 
  the 
  place, 
  their 
  origin 
  is 
  no 
  longer 
  in 
  doubt 
  ; 
  but 
  the 
  

   freshet 
  of 
  last 
  May 
  disclosed 
  the 
  nature 
  of 
  these 
  deposits 
  per- 
  

   fectly, 
  as 
  the 
  torrential 
  state 
  of 
  Nescopeck 
  creek 
  which 
  reaches 
  

   the 
  river 
  opposite 
  to 
  Berwick, 
  cut 
  away 
  ten 
  feet 
  of 
  the 
  north 
  

   bank 
  of 
  the 
  creek 
  at 
  the 
  Pennsylvania 
  R.R. 
  bridge 
  ; 
  so 
  that 
  

   the 
  north 
  abutment 
  was 
  isolated 
  and 
  undermined. 
  As 
  this 
  cut 
  

   was 
  vertical 
  and 
  the 
  material 
  compact 
  it 
  was 
  seen 
  that 
  there 
  

   was 
  the 
  same 
  succession 
  of 
  events 
  as 
  shown 
  in 
  the 
  Lehigh 
  

   Yalley 
  at 
  Rauch's 
  gravel 
  pit. 
  There 
  are 
  three 
  formations 
  in 
  

   the 
  gravels 
  at 
  Nescopeck 
  and 
  Berwick 
  : 
  first, 
  sub-glacial 
  till 
  so 
  

   compact 
  that 
  a 
  pick 
  can 
  scarcely 
  be 
  driven 
  into 
  it. 
  This 
  has 
  a 
  

   clay 
  base 
  and 
  carries 
  an 
  abundance 
  of 
  rolled 
  stones 
  of 
  all 
  the 
  

   formations 
  to 
  the 
  north 
  — 
  even 
  granite 
  and 
  anthracite 
  meet 
  in 
  

   the 
  mass. 
  On 
  this 
  is 
  a 
  'bed 
  of 
  modified 
  drift 
  of 
  loose 
  nature 
  

   and 
  sandy 
  matrix 
  with 
  the 
  same 
  collection 
  of 
  rolled 
  stones 
  and 
  

   of 
  equal 
  freshness. 
  In 
  fact, 
  there 
  is 
  no 
  difference 
  in 
  the 
  color 
  

   of 
  the 
  layers. 
  As 
  at 
  Rauch's 
  pit 
  the 
  lower 
  inch 
  of 
  the 
  gravels 
  

   is 
  a 
  conglomerate 
  with 
  a 
  limonite 
  matrix, 
  where 
  the 
  percolat- 
  

   ing 
  waters 
  laden 
  with 
  the 
  solution 
  of 
  iron 
  were 
  stopped 
  by 
  the 
  

   dense 
  till 
  below. 
  Capping 
  all 
  is 
  a 
  layer 
  of 
  unstratified 
  sand 
  

   that 
  varies 
  in 
  thickness 
  greatly 
  within 
  a 
  few 
  feet, 
  and 
  carries 
  

   streaks 
  of 
  gravel 
  and 
  glaciated 
  cobbles 
  and 
  bowlders 
  at 
  all 
  

   levels. 
  We 
  have, 
  therefore, 
  the 
  till 
  from 
  the 
  ice 
  on 
  the 
  spot, 
  

   and 
  the 
  modified 
  drift 
  when 
  the 
  ice 
  was 
  in 
  retreat 
  ; 
  but 
  in 
  the 
  

   vicinity, 
  and, 
  finally, 
  the 
  sands, 
  when 
  the 
  ice 
  had 
  retreated 
  to 
  a 
  

   distance 
  and 
  the 
  torrential 
  nature 
  of 
  the 
  stream 
  had 
  ceased 
  ; 
  

   but 
  when 
  there 
  still 
  were 
  discharged 
  bergs 
  bearing 
  burden 
  of 
  

   large 
  material. 
  It 
  is 
  about 
  20 
  feet 
  from 
  the 
  rock 
  bottom 
  of 
  

   the 
  river 
  to 
  the 
  top 
  of 
  the 
  sandy 
  cap. 
  

  

  There 
  are 
  several 
  low 
  kames 
  along 
  the 
  north 
  branch 
  ; 
  but 
  

   their 
  formation 
  could 
  not 
  be 
  studied 
  from 
  absence 
  of 
  cuttings. 
  

  

  The 
  ice 
  crossed 
  the 
  valley 
  of 
  the 
  west 
  branch 
  from 
  North- 
  

   umberland 
  to 
  Muncy 
  at 
  the 
  same 
  angle 
  as 
  in 
  the 
  other 
  branch, 
  

   and 
  the 
  formations 
  are 
  similar 
  in 
  succession 
  ; 
  but 
  from 
  Muncy 
  

   westward 
  a 
  slack 
  water-cap 
  hides 
  whatever 
  is 
  below, 
  and 
  it 
  is 
  

   only 
  where 
  the 
  cuttings 
  are 
  fresh 
  that 
  the 
  succession 
  can 
  be 
  

   seen. 
  

  

  In 
  the 
  main 
  valley 
  the 
  southern 
  limit 
  of 
  the 
  ice 
  was 
  where 
  

   Little 
  Mountain 
  reaches 
  the 
  river. 
  As 
  this 
  rises 
  abruptly 
  1000 
  

   feet 
  above 
  the 
  country 
  it 
  proved 
  an 
  effectual 
  barrier 
  to 
  a 
  

   farther 
  southern 
  advance. 
  The 
  glacier 
  crossed 
  the 
  river 
  and 
  

   seems 
  to 
  have 
  reached 
  the 
  northeastern 
  end 
  of 
  Shade 
  Mountain, 
  

   as 
  there 
  was 
  a 
  slight 
  flow 
  southwestward 
  over 
  the 
  low 
  col 
  of 
  

   200 
  feet 
  into 
  the 
  Juniata 
  at 
  Lewistown. 
  Evidences 
  of 
  glacia- 
  

  

  