﻿GEOLOGY 
  OF 
  THOUSAND 
  ISLANDS 
  REGION 
  99 
  

  

  limestones 
  at 
  Adams 
  just 
  about 
  compensates 
  for 
  the 
  disappearance 
  

   of 
  the 
  Potsdam 
  and 
  Theresa 
  formations 
  there, 
  and 
  that 
  the 
  dip 
  is 
  

   substantially 
  the 
  same 
  as 
  the 
  fall 
  of 
  the 
  rock 
  floor, 
  or 
  24 
  feet 
  per 
  

   mile. 
  At 
  most 
  there 
  is 
  a 
  deduction 
  of 
  but 
  100 
  feet 
  to 
  be 
  made, 
  

   amounting 
  to 
  3 
  feet 
  a 
  mile 
  in 
  30 
  miles, 
  and 
  reducing 
  the 
  total 
  to 
  21 
  

   feet 
  per 
  mile. 
  If, 
  as 
  is 
  likely, 
  this 
  is 
  still 
  not 
  the 
  direction 
  of 
  true 
  

   dip, 
  being 
  too 
  nearly 
  due 
  south, 
  the 
  figure 
  must 
  be 
  somewhat 
  en- 
  

   larged, 
  and 
  in 
  all 
  likelihood 
  it 
  amounts 
  to 
  from 
  25 
  to 
  30 
  feet 
  per 
  

   mile, 
  certainly 
  not 
  exceeding 
  35 
  feet. 
  

  

  It 
  is 
  of 
  interest 
  to 
  note 
  that 
  this 
  dip, 
  and 
  this 
  slope 
  of 
  the 
  

   Precambric 
  floor, 
  are 
  much 
  less 
  than 
  those 
  worked 
  out 
  in 
  the 
  

   upper 
  Mohawk 
  valley 
  by 
  Miller 
  and 
  myself 
  (Remsen 
  and 
  Little 
  

   Falls 
  quadrangles) 
  where 
  the 
  dips 
  approach 
  100 
  feet 
  per 
  mile 
  to 
  

   the 
  southwest, 
  and 
  the 
  Precambric 
  floor 
  underneath 
  has 
  a 
  slope 
  

   exceeding 
  that 
  of 
  the 
  dip 
  by 
  some 
  30 
  feet. 
  The 
  matter 
  of 
  the 
  

   present 
  dips 
  is 
  simply 
  the 
  sum 
  total 
  of 
  tipping 
  given 
  to 
  the 
  rocks 
  

   since 
  they 
  were 
  deposited, 
  by 
  the 
  various 
  oscillatory 
  movements 
  

   to 
  which 
  each 
  region 
  has 
  been 
  subjected 
  since; 
  showing 
  that 
  the 
  

   Mohawk 
  rocks 
  have 
  been 
  somewhat 
  more 
  tipped 
  than 
  those 
  

   here. 
  The 
  matter 
  of 
  floor 
  slope 
  however 
  show^s 
  clearly 
  that 
  the 
  

   shore 
  line 
  in 
  the 
  Mohawk 
  region 
  had 
  a 
  somewhat 
  greater 
  cant 
  

   than 
  was 
  the 
  case 
  here^ 
  producing 
  more 
  rapid 
  overlap 
  of 
  the 
  

   rocks 
  there. 
  

  

  In 
  the 
  northeast 
  portion 
  of 
  the 
  Alexandria 
  sheet 
  the 
  dip 
  has 
  

   flattened 
  out 
  to 
  practical 
  horizontality, 
  Potsdam 
  with 
  overly- 
  

   ing 
  Theresa 
  forming 
  the 
  river 
  bluffs. 
  Going 
  east, 
  down 
  the 
  

   river, 
  the 
  dip 
  soon 
  changes 
  to 
  the 
  northeast, 
  carrying 
  these 
  

   formations 
  beneath 
  the 
  water 
  and 
  the 
  westerly 
  edge 
  of 
  the 
  Beek- 
  

   mantown 
  becomes 
  the 
  surface 
  rock, 
  beyond 
  which, 
  for 
  many 
  

   miles, 
  the 
  river 
  flows 
  through 
  Beekmantown 
  rocks, 
  all 
  with 
  

   slight 
  northerly 
  dip. 
  These 
  are 
  the 
  deposits 
  of 
  the 
  eastern 
  basin, 
  

   and 
  received 
  no 
  tilt 
  to 
  the 
  west. 
  

  

  ROCK 
  STRUCTURES^ 
  

   Foliation 
  

  

  Foliation 
  is 
  the 
  name 
  applied 
  to 
  the 
  species 
  of 
  cleavage 
  de- 
  

   veloped 
  in 
  rocks 
  which, 
  under 
  compression, 
  have 
  wholly 
  or 
  

   largely 
  recrystallized. 
  The 
  cleavage 
  is 
  chiefly 
  due 
  to 
  the 
  ar- 
  

   rangement 
  which 
  the 
  compression 
  enforces 
  on 
  many 
  of 
  the 
  re- 
  

   crystallizing 
  minerals, 
  which 
  tend 
  to 
  develop 
  in 
  the 
  shape 
  of 
  

  

  1 
  By 
  H. 
  P. 
  Gushing. 
  

   4 
  

  

  