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  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1927 
  

  

  (7) 
  During 
  pauses 
  in 
  the 
  recession 
  of 
  the 
  ice 
  front 
  the 
  heavy 
  load 
  

   of 
  rock 
  rubbish 
  was 
  piled 
  in 
  the 
  valleys. 
  One 
  great 
  series 
  of 
  these 
  

   frontal 
  moraines 
  is 
  the 
  heavy 
  fillings 
  south 
  of 
  the 
  lakes. 
  Another 
  

   forms 
  the 
  wide 
  plain 
  that 
  buries 
  the 
  north 
  ends 
  of 
  the 
  valleys 
  and 
  

   produces 
  the 
  lake 
  basins. 
  (See 
  fig. 
  2.) 
  

  

  (8) 
  Northward 
  uptilting 
  of 
  the 
  land 
  since 
  the 
  weight 
  of 
  the 
  ice 
  

   cap 
  has 
  been 
  removed 
  has 
  lifted 
  the 
  north 
  ends 
  of 
  the 
  lakes, 
  thus 
  pro- 
  

   ducing 
  some 
  increase 
  in 
  their 
  depth. 
  

  

  (9) 
  The 
  filling 
  process, 
  by 
  inwash 
  of 
  detritus 
  and 
  the 
  accumula- 
  

   tion 
  of 
  peat, 
  has 
  already 
  obliterated 
  some 
  of 
  the 
  shallower 
  lakes, 
  

   and 
  has 
  made 
  a 
  beginning 
  on 
  the 
  destruction 
  of 
  the 
  remaining 
  lakes. 
  

   Witness 
  the 
  extensive 
  plains 
  at 
  the 
  heads 
  of 
  Canandaigua, 
  Seneca, 
  

   Cayuga, 
  and 
  Owasco 
  Lakes. 
  (Fig. 
  4.) 
  

  

  