﻿THE 
  GEOLOGICAL 
  HISTORY 
  OF 
  NEW 
  YORK 
  STATE 
  103 
  

  

  cases 
  of 
  the 
  two 
  largest 
  lakes, 
  Seneca 
  and 
  Cayuga, 
  there 
  is, 
  how- 
  

   ever, 
  strong 
  evidence 
  that 
  the 
  preglacial 
  channels 
  were 
  notably 
  

   deepened 
  by 
  ice 
  erosion. 
  1 
  As 
  Professor 
  Tarr 
  says 
  : 
  " 
  They 
  offered 
  

   broad 
  channel 
  ways, 
  along 
  which 
  the 
  ice 
  streams 
  moved 
  much 
  more 
  

   easily 
  than 
  upon 
  the 
  neighboring 
  irregular 
  hilltops. 
  Not 
  only 
  was 
  

   the 
  movement 
  more 
  rapid, 
  but 
  the 
  depth 
  of 
  ice 
  was 
  greater. 
  The 
  

   position 
  of 
  the 
  rocks, 
  dipping 
  southward, 
  and 
  the 
  nature 
  of 
  the 
  

   friable 
  shales 
  conspired 
  toward 
  rapid 
  erosion 
  ; 
  and 
  so 
  these 
  north 
  

   and 
  south 
  preglacial 
  valleys 
  were 
  markedly 
  deepened. 
  Evidence 
  of 
  

   this 
  comes 
  from 
  the 
  side 
  streams. 
  The 
  rock 
  bottoms 
  of 
  the 
  pre- 
  

   glacial 
  valleys 
  of 
  these 
  tributary 
  streams 
  are 
  not 
  now 
  below 
  the 
  

   level 
  of 
  the 
  lake 
  water 
  in 
  the 
  southern 
  part 
  of 
  the 
  valley 
  (Cayuga). 
  

   If 
  all 
  the 
  drift 
  could 
  be 
  removed 
  and 
  the 
  streams 
  be 
  allowed 
  to 
  

   flow 
  along 
  the 
  line 
  of 
  the 
  course 
  of 
  the 
  preglacial 
  valleys 
  and 
  enter 
  

   the 
  valley 
  of 
  Lake 
  Cayuga 
  as 
  it 
  now 
  stands, 
  excepting 
  that 
  it 
  be 
  

   robbed 
  of 
  water, 
  they 
  would 
  tumble 
  between 
  300 
  and 
  400 
  feet 
  in 
  a 
  

   distance 
  of 
  about 
  a 
  mile, 
  commencing 
  their 
  descent 
  near 
  the 
  present 
  

   lake 
  margin, 
  a 
  most 
  unnatural 
  condition 
  for 
  mature 
  tributaries 
  

   near 
  their 
  mouth." 
  2 
  Thus 
  it 
  appears 
  quite 
  certain 
  that 
  the 
  pre- 
  

   glacial 
  Cayuga 
  and 
  Seneca 
  valleys, 
  at 
  least, 
  were 
  notably 
  deepened 
  

   by 
  ice 
  erosion 
  below 
  the 
  level 
  of 
  the 
  mouths 
  of 
  the 
  preglacial 
  

   tributary 
  streams. 
  

  

  Most 
  of 
  the 
  numerous 
  Adirondack 
  lakes 
  have 
  certainly 
  been 
  

   formed 
  by 
  irregular 
  damming 
  of 
  preglacial 
  valleys 
  by 
  glacial 
  drift. 
  

   It 
  is 
  quite 
  the 
  rule 
  to 
  find 
  the 
  outlets 
  of 
  these 
  lakes 
  flowing 
  through 
  

   such 
  loose 
  materials. 
  By 
  ice 
  erosion 
  many 
  of 
  the 
  favorably 
  situated 
  

   valleys 
  were 
  no 
  doubt 
  somewhat 
  modified, 
  but 
  up 
  to 
  the 
  present 
  

   time 
  we 
  have 
  no 
  good 
  example 
  of 
  a 
  lake 
  basin 
  produced 
  by 
  that 
  

   agency. 
  The 
  hard 
  Precambrie 
  rocks 
  were 
  not 
  so 
  easily 
  eroded 
  by 
  

   the 
  ice. 
  Attention 
  is 
  called 
  to 
  the 
  prominent 
  lake 
  belt 
  in 
  the 
  middle 
  

   of 
  the 
  Adirondack 
  province, 
  and 
  running 
  in 
  a 
  north-northeast 
  by 
  

   south-southwest 
  direction. 
  This 
  belt 
  comprises 
  many 
  well-known 
  

   lakes 
  as 
  Placid, 
  Saranac, 
  Tupper, 
  "Long, 
  Blue 
  Mountain, 
  Big 
  Moose, 
  

   and 
  Fulton 
  Chain 
  lakes. 
  Sometimes 
  small 
  lakes 
  or 
  ponds 
  are 
  situ- 
  

   ated 
  well 
  toward 
  mountain 
  tops 
  because 
  of 
  favorably 
  located 
  drift 
  

   deposits. 
  A 
  good 
  example 
  of 
  such 
  lake 
  lies 
  at 
  an 
  altitude 
  of 
  2620 
  

   feet, 
  and 
  well 
  toward 
  the 
  top 
  of 
  Crane 
  mountain 
  in 
  Warren 
  county. 
  

  

  1 
  The 
  surfaces 
  of 
  Seneca 
  and 
  Cayuga 
  lakes 
  are 
  respectively 
  444 
  and 
  381 
  

   feet 
  above 
  sea 
  level, 
  while 
  their 
  deepest 
  places 
  are 
  respectively 
  186 
  and 
  119 
  

   feet 
  below 
  sea 
  level. 
  

  

  2 
  Tarr's 
  Physical 
  Geography 
  of 
  New 
  York 
  State, 
  p. 
  181-82. 
  

  

  