﻿of 
  the 
  Northern 
  Appalachians. 
  41T 
  

  

  In 
  one 
  of 
  his 
  last 
  papers 
  — 
  "Rhythms 
  and 
  the 
  Measure- 
  

   ment 
  of 
  Geologic 
  Time" 
  34 
  — 
  Professor 
  Barrell 
  described, 
  

   however, 
  a 
  type 
  of 
  movement 
  involving 
  "progressive 
  

   tilting 
  combined 
  with 
  rhythmic 
  oscillation 
  of 
  baselevel" 
  

   which 
  he 
  illustrated 
  by 
  the 
  relation 
  of 
  the 
  formations 
  of 
  

   the 
  Atlantic 
  Coastal 
  Plain 
  and 
  which 
  an 
  unfinished 
  draw- 
  

   ing 
  shows 
  he 
  also 
  applied 
  to 
  the 
  New 
  England 
  region. 
  

   When 
  the 
  entire 
  Appalachian 
  Province 
  is 
  considered 
  it 
  

   is 
  to 
  be 
  presumed 
  that 
  progressive 
  doming 
  at 
  an 
  irreg- 
  

   ular 
  rate 
  combined 
  with 
  recurrent 
  phases 
  of 
  emergence 
  

   and 
  submergence 
  of 
  the 
  land 
  would 
  more 
  nearly 
  describe 
  

   the 
  actual 
  character 
  of 
  the 
  crustal 
  movement. 
  

  

  The 
  attitude 
  of 
  the 
  Pliocene 
  and 
  Pleistocene 
  terraces 
  

   may 
  be 
  considered 
  in 
  general 
  agreement 
  with 
  the 
  concep- 
  

   tion 
  of 
  the 
  crustal 
  movement 
  as 
  stated 
  in 
  the 
  foregoing 
  

   paper, 
  because 
  on 
  the 
  basis 
  of 
  accepted 
  conclusions 
  tilting 
  

   had 
  nearly 
  ceased 
  by 
  the 
  close 
  of 
  the 
  Miocene. 
  It 
  would 
  

   seem, 
  however, 
  as 
  though 
  the 
  Becket, 
  Canaan, 
  and 
  Corn- 
  

   wall 
  restored 
  terraces 
  should 
  have 
  steeper 
  slopes 
  than 
  

   the 
  younger 
  terraces 
  because 
  they 
  were 
  cut 
  on 
  the 
  flank 
  

   of 
  the 
  domed 
  area 
  where 
  the 
  effect 
  of 
  later 
  tilting 
  should 
  

   be 
  recognizable. 
  The 
  reason 
  for 
  this 
  apparent 
  discrep- 
  

   ancy 
  is 
  not 
  clear. 
  It 
  is 
  possible 
  that 
  the 
  profile 
  antedates 
  

   the 
  conception 
  of 
  the 
  crustal 
  movement, 
  the 
  former 
  was 
  

   drawn 
  in 
  1912 
  whereas 
  the 
  latter 
  was 
  not 
  published 
  until 
  

   1916, 
  or 
  the 
  record 
  may 
  have 
  been 
  considered 
  too 
  com- 
  

   plex 
  to 
  be 
  adequately 
  represented. 
  A 
  reason 
  of 
  a 
  differ- 
  

   ent 
  nature 
  concerns 
  the 
  suitability 
  of 
  existing 
  residuals 
  

   for 
  the 
  restoration 
  of 
  the 
  oldest 
  terraces, 
  a 
  point 
  that 
  

   Professor 
  Barrell 
  recognized 
  and 
  that 
  has 
  been 
  touched 
  

   upon. 
  

  

  The 
  suggestion 
  may 
  be 
  noted 
  here 
  that 
  if 
  the 
  attitude 
  

   of 
  the 
  terraces 
  is 
  correctly 
  shown 
  and 
  if 
  tilting 
  was 
  as 
  

   pronounced 
  in 
  southern 
  New 
  England 
  as 
  it 
  was 
  farther 
  

   south 
  — 
  the 
  scanty 
  well 
  records 
  appear 
  to 
  show 
  that 
  it 
  

   was 
  — 
  then 
  the 
  unfitted 
  position 
  of 
  the 
  highest 
  terraces 
  

   may 
  indicate 
  a 
  much 
  younger 
  age 
  for 
  them 
  than 
  has 
  been 
  

   assigned. 
  

  

  A 
  careful 
  study 
  of 
  the 
  profile 
  and 
  maps 
  both 
  topo- 
  

   graphic 
  and 
  geologic, 
  coupled 
  with 
  some 
  acquaintance 
  

   with 
  the 
  region, 
  has 
  left 
  the 
  definite 
  impression 
  that 
  Pro- 
  

   fessor 
  Barrell's 
  conclusion 
  as 
  to 
  the 
  marine 
  origin 
  of 
  the 
  

   terraces 
  below 
  the 
  Cornwall 
  is 
  well 
  taken. 
  Also, 
  if 
  

   the 
  topographic 
  break 
  between 
  the 
  Becket 
  terrace 
  and 
  

  

  34 
  Bull. 
  Geol. 
  Soc. 
  Amer., 
  vol. 
  28, 
  pp. 
  789-795, 
  1917. 
  

  

  