﻿1^.2 
  NEW 
  YORK 
  STAtE 
  MUSEUM 
  

  

  overlooking 
  the 
  Precambric 
  areas 
  to 
  the 
  northward. 
  The 
  drainage 
  

   is 
  to 
  the 
  southwest 
  and 
  passes 
  from 
  the 
  Precambric 
  into 
  the 
  Paleo- 
  

   zoic 
  limestone 
  country, 
  the 
  streams 
  deeply 
  notching 
  the 
  cuesta 
  front 
  

   as 
  they 
  pass 
  into 
  it. 
  Of 
  the 
  lakes 
  he 
  says 
  : 
  ''In 
  most 
  cases 
  the 
  

   upper 
  parts 
  of 
  these 
  valleys, 
  near 
  where 
  they 
  pass 
  through 
  the 
  

   cuesta 
  front, 
  form 
  the 
  basins 
  of 
  long, 
  narrow 
  lakes. 
  The 
  water 
  

   seems 
  in 
  some 
  cases 
  to 
  be 
  held 
  back 
  by 
  a 
  drift 
  dam, 
  which 
  partly 
  

   blocks 
  the 
  lower 
  part 
  of 
  the 
  valley. 
  Certainly 
  in 
  some 
  cases, 
  in 
  all 
  

   probabiHty 
  in 
  most 
  cases, 
  the 
  present 
  lake 
  basin 
  is 
  a 
  rock 
  basin 
  

   and 
  the 
  existence 
  of 
  the 
  present 
  lake 
  is 
  due 
  either 
  to 
  warping 
  or 
  

   possibly 
  to 
  differential 
  erosion 
  by 
  ice.^ 
  " 
  

  

  In 
  this 
  district 
  of 
  Wilson's 
  the 
  Potsdam 
  and 
  Theresa 
  formations 
  

   are 
  absent, 
  the 
  Pamelia, 
  or 
  Lowville, 
  resting 
  on 
  the 
  Precambric, 
  

   forming 
  a 
  single 
  cuesta 
  front 
  that 
  is 
  more 
  prominent 
  than 
  those 
  in 
  

   our 
  district. 
  The 
  lakes 
  on 
  the 
  Alexandria 
  sheet 
  have 
  their 
  beds 
  

   either 
  on 
  Precambric 
  or 
  on 
  Potsdam, 
  and 
  the 
  limestone 
  front 
  is 
  

   more 
  or 
  less 
  remote. 
  They 
  nestle 
  in 
  the 
  extreme 
  upper 
  portions 
  of 
  

   the 
  valley 
  heads 
  on 
  the 
  north 
  side 
  of 
  the 
  divide 
  which 
  runs 
  through 
  

   the 
  region, 
  and 
  has 
  just 
  been 
  described. 
  They 
  are 
  in 
  the 
  extreme 
  

   upper 
  portions 
  of 
  the 
  valleys 
  of 
  north-flowing 
  streams, 
  instead 
  of 
  

   occupying 
  a 
  special 
  position 
  in 
  the 
  valleys 
  of 
  southerly 
  streams, 
  as 
  

   in 
  the 
  case 
  of 
  the 
  Ontarian 
  lakes, 
  and 
  in 
  this 
  lies 
  their 
  chief 
  dif- 
  

   ference 
  from 
  those. 
  Hyde 
  lake, 
  in 
  the 
  northern 
  portion 
  of 
  the 
  

   Theresa 
  sheet, 
  conforms 
  more 
  nearly 
  to 
  the 
  Ontarian 
  type, 
  though 
  

   in 
  Potsdam 
  instead 
  of 
  Precambric, 
  and 
  Perch 
  lake 
  seems 
  the 
  shallow 
  

   remnant 
  of 
  another 
  lake 
  of 
  similar 
  type. 
  The 
  Alexandrian 
  lakes, 
  

   however, 
  differ 
  as 
  specified, 
  and 
  herein 
  lies 
  also 
  the 
  reason 
  for 
  their 
  

   localization. 
  The 
  old 
  divide 
  runs 
  into 
  higher 
  ground 
  passing 
  east- 
  

   ward, 
  and 
  the 
  relations 
  of 
  the 
  rocks 
  shift. 
  The 
  streams 
  there 
  rise 
  

   in 
  the 
  Precambric 
  and 
  run 
  northward 
  into 
  the 
  Paleozoic 
  rocks 
  of 
  

   the 
  St 
  Lawrence 
  valley, 
  while 
  our 
  lake 
  valleys 
  here 
  commence 
  in 
  

   Potsdam 
  and 
  run 
  north 
  into 
  Precambric. 
  

  

  Most 
  of 
  the 
  lakes 
  seem 
  to 
  be 
  in 
  rock 
  basins, 
  Crystal, 
  Sixberry 
  

   and 
  Millsite 
  certainly 
  are, 
  and 
  Butterfield 
  probably 
  is. 
  Crystal 
  lake 
  

   is 
  entirely 
  in 
  Potsdam 
  though 
  its 
  bed 
  may 
  be 
  on 
  the 
  Precambric, 
  

   and 
  is 
  walled 
  by 
  high 
  and 
  continuous 
  sandstone 
  cHffs, 
  with 
  the 
  

   shainply 
  cut 
  valley 
  head 
  but 
  a 
  short 
  distance 
  back 
  from 
  the 
  lake 
  

   margin 
  [pi. 
  34]. 
  Sixberry, 
  Millsite 
  and 
  Butterfield 
  are 
  partly 
  

   walled 
  by 
  Potsdam, 
  with 
  characteristic 
  cliffs, 
  and 
  with 
  valley 
  heads 
  

   cut 
  in 
  Potsdam, 
  but 
  with 
  their 
  beds 
  in 
  Precambric 
  [pi. 
  54]. 
  The 
  

   beds 
  of 
  the 
  two 
  latter 
  are 
  in 
  large 
  part 
  in 
  Grenville 
  limestone. 
  Six- 
  

  

  !■ 
  Op. 
  cit. 
  p. 
  217. 
  

  

  