﻿412 
  J. 
  Barrell 
  — 
  The 
  Piedmont 
  Terraces 
  

  

  longed 
  resistance 
  of 
  marine 
  peneplanes 
  to 
  subaerial 
  

   erosion 
  are 
  as 
  follows. 
  When 
  a 
  prolonged 
  cycle 
  of 
  flu- 
  

   vial 
  denudation 
  has 
  passed, 
  leaving 
  the 
  softer 
  formations 
  

   as 
  lowland 
  plains 
  and 
  the 
  harder 
  formations 
  as 
  promi- 
  

   nent 
  interfluvial 
  ridges, 
  submergence 
  to 
  about 
  200 
  feet 
  

   will 
  produce 
  wide 
  embayments 
  over 
  the 
  softer 
  forma- 
  

   tions 
  and 
  will 
  give 
  rise 
  to 
  chains 
  of 
  islands 
  where 
  monad- 
  

   nocks 
  rise 
  above 
  the 
  surface 
  of 
  the 
  harder 
  formations. 
  

   Let 
  the 
  submergence 
  be 
  prolonged 
  and 
  these 
  islands 
  will 
  

   be 
  eroded 
  to 
  a 
  markedly 
  uniform 
  level, 
  giving 
  an 
  accord- 
  

   ant 
  series 
  of 
  broad 
  hilltops 
  on 
  the 
  formations 
  best 
  suited 
  

   to 
  preserve 
  them. 
  A 
  small 
  subsequent 
  uplift, 
  with 
  cor- 
  

   respondingly 
  gentle 
  grades 
  in 
  the 
  master 
  streams, 
  will 
  

   greatly 
  lengthen 
  the 
  endurance 
  of 
  these 
  platforms 
  

   through 
  later 
  time. 
  

  

  The 
  rock 
  benches 
  in 
  general 
  will 
  keep 
  some 
  portion 
  of 
  

   their 
  veneer 
  of 
  gravel 
  until 
  erosion 
  has 
  reached 
  maturity 
  

   in 
  a 
  later 
  cycle. 
  Before 
  the 
  rock 
  floor 
  of 
  the 
  marine 
  

   benches 
  can 
  be 
  eroded 
  the 
  adjacent 
  surface 
  slopes 
  must 
  

   be 
  destroyed, 
  soil 
  and 
  gravel 
  must 
  creep 
  down 
  to 
  the 
  

   stream 
  channels 
  and 
  be 
  swept 
  away. 
  The 
  last 
  traces 
  of 
  

   the 
  veneer 
  will 
  be 
  found 
  in 
  favored 
  situations. 
  On 
  the 
  

   nearly 
  flat 
  hilltops 
  the 
  largest 
  cobbles 
  will 
  stay 
  longest 
  

   as 
  residual 
  bowlders. 
  Also 
  at 
  the 
  base 
  of 
  former 
  cliffs 
  

   wave-rolled 
  gravel 
  may 
  be 
  protected 
  for 
  a 
  time 
  because 
  

   of 
  burial 
  under 
  talus. 
  Even 
  the 
  marginal 
  conglomerates 
  

   may 
  form 
  masses 
  of 
  considerable 
  resistance. 
  Fluviatile 
  

   conglomerates 
  may 
  predominate 
  at 
  first 
  over 
  those 
  of 
  

   marine 
  origin, 
  but 
  such 
  are 
  deposited 
  in 
  places 
  favorable 
  

   for 
  early 
  removal 
  during 
  the 
  following 
  cycle 
  of 
  erosion. 
  

   The 
  true 
  marine 
  conglomerates 
  deposited 
  on 
  wave-cut 
  

   benches 
  though 
  less 
  in 
  quantity 
  are 
  more 
  favorably 
  situ- 
  

   ated 
  for 
  preservation. 
  

  

  Editorial 
  note 
  on 
  the 
  projected 
  profile 
  of 
  the 
  terraces 
  of 
  western 
  

   Massachusetts 
  and 
  Connecticut. 
  

  

  The 
  projected 
  profile 
  of 
  the 
  New 
  England 
  terraces, 
  as 
  

   they 
  are 
  developed 
  in 
  western 
  Massachusetts 
  and 
  Con- 
  

   necticut, 
  is 
  shown 
  by 
  pi. 
  V; 
  it 
  extends 
  in 
  a 
  north-south 
  

   direction 
  from 
  Mount 
  Graylock 
  to 
  Long 
  Island 
  Sound 
  and 
  

   embraces 
  an 
  area 
  90 
  by 
  17 
  miles. 
  In 
  order 
  to 
  bring 
  out 
  

   the 
  terraces 
  to 
  best 
  advantage 
  a 
  direction 
  of 
  view 
  N 
  55° 
  

   E 
  was 
  chosen, 
  which 
  is 
  approximately 
  parallel 
  to 
  their 
  

   trend, 
  and 
  the 
  vertical 
  scale 
  was 
  greatly 
  exaggerated. 
  

  

  