﻿182 
  E. 
  H. 
  Williams 
  — 
  Southern 
  Ice 
  Limit 
  in 
  Pennsylvania. 
  

  

  have 
  been 
  found 
  at 
  all 
  elevations 
  over 
  the 
  mountain. 
  As 
  they 
  

   stop, 
  at 
  the 
  mountain 
  foot, 
  and 
  as 
  the 
  till 
  on 
  the 
  flanks 
  and 
  top 
  

   is 
  angular 
  and 
  from 
  the 
  immediate 
  neighboring 
  formations, 
  or 
  

   consists 
  of 
  large 
  bowlders 
  of 
  the 
  sandstones 
  to 
  the 
  north, 
  it 
  is 
  

   evident 
  that 
  the 
  lower 
  part 
  of 
  the 
  ice 
  moved 
  parallel 
  to 
  the 
  

   river 
  and 
  mountain, 
  while 
  the 
  upper 
  part 
  crossed 
  the 
  ridge 
  and 
  

   probably 
  united 
  with 
  the 
  lobe 
  that 
  came 
  from 
  the 
  east 
  along 
  

   the 
  enclosed 
  valley 
  south 
  of 
  Nescopeck 
  Mountain. 
  

  

  The 
  glacial 
  gravels 
  of 
  the 
  Juniata 
  valley. 
  

  

  While 
  studying 
  the 
  deposits 
  in 
  the 
  valley 
  of 
  the 
  Susque- 
  

   hanna, 
  the 
  writer 
  followed 
  a 
  line 
  of 
  drainage 
  over 
  the 
  low 
  

   divide 
  between 
  the 
  Susquehanna 
  at 
  Selin's 
  Grove 
  and 
  the 
  

   Juniata 
  at 
  Lewistown 
  ; 
  but 
  was 
  surprised 
  to 
  find 
  on 
  the 
  Salina 
  

   bluffs 
  south 
  of 
  the 
  river, 
  at 
  the 
  latter 
  place, 
  a 
  series 
  of 
  lenticu- 
  

   lar 
  deposits 
  of 
  glacial 
  gravels 
  and 
  bowlders 
  in 
  the 
  depressions 
  

   and 
  on 
  the 
  down-river 
  side 
  of 
  the 
  elevations 
  of 
  those 
  bluffs, 
  

   and 
  at 
  heights 
  up 
  to 
  80 
  feet 
  above 
  the 
  river. 
  Their 
  position 
  

   pointed 
  to 
  an 
  origin 
  up 
  the 
  Juniata 
  ; 
  but 
  as 
  I 
  was 
  engaged 
  in 
  

   regular 
  work, 
  I 
  let 
  that 
  matter 
  go 
  for 
  the 
  time 
  ; 
  but 
  looked 
  up 
  

   the 
  authorities 
  and 
  found 
  that 
  I. 
  C. 
  White, 
  in 
  his 
  report 
  for 
  

   Huntingdon 
  county 
  in 
  the 
  recent 
  survey 
  of 
  the 
  State, 
  noted 
  

   their 
  appearance 
  in 
  that 
  county, 
  and 
  advanced 
  four 
  theories 
  for 
  

   their 
  origin 
  ; 
  but 
  without 
  favoring 
  either 
  of 
  them 
  ; 
  while 
  those 
  

   who 
  worked 
  in 
  Mifflin 
  and 
  Juniata 
  counties 
  said 
  nothing 
  of 
  

   the 
  occurrence 
  of 
  gravels 
  at 
  such 
  high 
  elevations. 
  

  

  As 
  Professor 
  White* 
  had 
  also 
  reported 
  upon 
  the 
  counties 
  

   along 
  the 
  north 
  branch 
  of 
  the 
  Susquehanna, 
  he 
  was 
  in 
  a 
  posi- 
  

   tion 
  to 
  speak 
  regarding 
  glacial 
  deposits, 
  and 
  in 
  the 
  Huntingdon 
  

   report 
  (p. 
  31) 
  he 
  says, 
  "Great 
  heaps 
  of 
  bowlder 
  trash, 
  both 
  

   rounded 
  and 
  angular, 
  are 
  often 
  to 
  be 
  seen 
  along 
  the 
  valleys 
  of 
  

   the 
  principal 
  streams 
  ; 
  and 
  these 
  often 
  very 
  much 
  resemble 
  

   genuine 
  drift 
  heaps 
  ; 
  but 
  no 
  striated 
  bowlders 
  or 
  striated 
  frag- 
  

   ments 
  of 
  the 
  country 
  rock 
  are 
  to 
  be 
  found 
  in 
  the 
  region." 
  He 
  

   further 
  reports 
  them 
  at 
  elevations 
  above 
  100 
  feet 
  from 
  the 
  

   river. 
  The 
  hypotheses 
  advanced 
  are 
  various, 
  and 
  the 
  only 
  one 
  

   of 
  value 
  is 
  that 
  of 
  the 
  melting 
  snows 
  of 
  the 
  glacial 
  period 
  

   that 
  kept 
  all 
  the 
  rivers 
  of 
  the 
  State 
  at 
  a 
  higher 
  level 
  than 
  at 
  

   present. 
  Nothing 
  is 
  said 
  of 
  glacial 
  occupation 
  of 
  the 
  region. 
  

  

  * 
  Justice 
  to 
  Professor 
  White 
  requires 
  the 
  statement 
  that 
  his 
  work 
  in 
  the 
  recent 
  

   geological 
  survey 
  of 
  Pennsylvania 
  was 
  confined 
  to 
  counties 
  widely 
  separate 
  from 
  

   one 
  another 
  ; 
  so 
  that 
  the 
  study 
  of 
  a 
  limited 
  portion 
  of 
  the 
  Juniata 
  valley 
  would 
  

   afford 
  no 
  clew 
  to 
  the 
  origin 
  of 
  these 
  gravels, 
  had 
  it 
  not 
  been 
  supplemented 
  by 
  

   extended 
  work 
  over 
  a 
  large 
  adjacent 
  area. 
  The 
  writer 
  was 
  fortunate 
  in 
  having 
  

   the 
  careful 
  and 
  accurate 
  work 
  of 
  Professor 
  White 
  to 
  guide 
  him 
  in 
  the 
  study 
  of 
  

   the 
  north 
  branch 
  of 
  the 
  Susquehanna, 
  and 
  has 
  many 
  times 
  regretted 
  that 
  it 
  was 
  

   not 
  extended 
  to 
  the 
  south 
  and 
  west 
  ; 
  as 
  those 
  regions 
  were 
  treated 
  from 
  an 
  

   entirely 
  different 
  standpoint. 
  

  

  