﻿Il8 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  very 
  likely 
  source 
  of 
  such 
  additional 
  pressure 
  is 
  to 
  be 
  found 
  in 
  

   the 
  -well 
  known 
  oscillations 
  of 
  level 
  which 
  the 
  district 
  has 
  under- 
  

   gone 
  preceding, 
  during 
  and 
  since 
  glaciation. 
  The 
  general 
  dis- 
  

   trict 
  has 
  increased 
  its 
  altitude 
  by 
  some 
  400 
  feet 
  since 
  the 
  ice 
  dis- 
  

   appeared 
  from 
  the 
  St 
  Lawrence 
  valley, 
  and 
  this 
  change 
  is 
  simply 
  

   the 
  last 
  of 
  a 
  series 
  of 
  oscillations. 
  Furthermore 
  these 
  move- 
  

   ments 
  were 
  of 
  the 
  nature 
  of 
  warps, 
  the 
  changes 
  in 
  level 
  not 
  being 
  

   everywhere 
  the 
  same, 
  but 
  of 
  varying 
  amount. 
  Such 
  warping 
  

   must 
  bring 
  about 
  compression 
  in 
  some 
  tracts 
  and 
  stretching 
  in 
  

   others. 
  The 
  contraction 
  produced 
  in 
  the 
  rocks 
  by 
  the 
  cooling 
  of 
  

   the 
  ice 
  sheet 
  would 
  likely 
  have 
  manifested 
  itself 
  in 
  mere 
  slight 
  

   widening 
  along 
  the 
  joint 
  cracks, 
  and 
  side 
  compression 
  brought 
  

   about 
  by 
  warping 
  may 
  have 
  sufficed 
  locally 
  to 
  close 
  up 
  these 
  

   widened 
  joints. 
  In 
  such 
  case 
  postglacial 
  increase 
  of 
  tempera- 
  

   ture 
  might 
  well 
  tend 
  to 
  cause 
  buckling 
  of 
  the 
  rocks. 
  The 
  warp- 
  

   ing 
  is 
  of 
  such 
  nature 
  that 
  it 
  would 
  tend 
  to 
  produce 
  thrust 
  from 
  

   the 
  northeast, 
  and 
  it 
  is 
  to 
  be 
  noted 
  that 
  these 
  folds 
  trend 
  north- 
  

   west, 
  as 
  should 
  be 
  the 
  case 
  on 
  this 
  hypothesis. 
  

  

  There 
  at 
  once 
  arises, 
  however, 
  the 
  further 
  question 
  as 
  to 
  

   whether 
  the 
  compression 
  consequent 
  upon 
  warping 
  may 
  not 
  

   have 
  been 
  perfectly 
  competent 
  to 
  cause 
  the 
  buckling, 
  entirely 
  

   independently 
  of 
  any 
  effect 
  which 
  the 
  ice 
  may 
  have 
  had, 
  and 
  

   this 
  seems 
  to 
  the 
  writer 
  very 
  probable. 
  Dr 
  Reid, 
  in 
  correspond- 
  

   ence, 
  states 
  his 
  belief 
  that 
  " 
  we 
  must 
  fall 
  back 
  on 
  the 
  general 
  

   explanation 
  that 
  movements 
  of 
  the 
  crust 
  are 
  in 
  progress 
  which 
  

   have 
  produced 
  these 
  bucklings." 
  Dr 
  Branner 
  expresses 
  similar 
  

   views. 
  In 
  any 
  case, 
  until- 
  it 
  has 
  been 
  shown 
  that 
  lateral 
  spread- 
  

   ing 
  may 
  be 
  produced 
  in 
  rocks 
  of 
  this 
  resistant 
  type 
  by 
  load 
  no 
  

   greater 
  than 
  that 
  of 
  the 
  ice 
  sheet, 
  some 
  doubt 
  must 
  attach 
  to 
  the 
  

   competency 
  of 
  Gilbert's 
  hypothesis 
  as 
  applied 
  to 
  these 
  special 
  cases. 
  

  

  Faults 
  

  

  Faults 
  of 
  considerable 
  magnitude 
  and 
  importance 
  have 
  not 
  

   been 
  noted 
  in 
  the 
  district, 
  and 
  the 
  fairly 
  accurate 
  areal 
  mapping 
  

   which 
  the 
  abundant 
  rock 
  exposures 
  render 
  possible, 
  indicates 
  

   that 
  no 
  such 
  are 
  present, 
  at 
  least 
  in 
  the 
  Paleozoic 
  rocks. 
  Small 
  

   faults 
  appear, 
  however, 
  in 
  considerable 
  number 
  in 
  all 
  the 
  rocks 
  

   and 
  are 
  apparently 
  of 
  different 
  age. 
  

  

  In 
  the 
  Precambric 
  rocks. 
  Small 
  faults, 
  with 
  dislocations 
  of 
  

   from 
  a 
  fraction 
  of 
  an 
  inch 
  to 
  a 
  few 
  feet 
  occur 
  in 
  a 
  great 
  number 
  

   of 
  localities 
  in 
  the 
  Precambric 
  rocks, 
  as 
  already 
  pointed 
  out 
  by 
  

  

  