﻿E. 
  H. 
  Perkins 
  — 
  Dighton 
  Conglomerate. 
  75 
  

  

  As 
  time 
  went 
  on 
  the 
  climate 
  became 
  still 
  more 
  damp 
  

   and 
  cold. 
  There 
  were 
  climatic 
  fluctuations, 
  — 
  periods 
  of 
  

   rain 
  when 
  pebble 
  beds 
  were 
  carried 
  far 
  out 
  on 
  the 
  plains, 
  

   and 
  drier 
  periods 
  when 
  mud 
  and 
  sand 
  were 
  deposited, 
  — 
  

   but 
  all 
  the 
  time 
  the 
  tendency 
  was 
  toward 
  a 
  wetter 
  and 
  a 
  

   cooler 
  climate. 
  The 
  pebble 
  beds 
  increased 
  in 
  thickness 
  

   and 
  number 
  and 
  in 
  the 
  size 
  of 
  their 
  fragments. 
  Erosion 
  

   increased 
  in 
  the 
  headwaters. 
  Perhaps 
  as 
  the 
  cold 
  be- 
  

   came 
  more 
  intense 
  the 
  vegetation 
  became 
  less, 
  leaving 
  

   exposed 
  rock 
  surfaces 
  ; 
  perhaps 
  the 
  mountains 
  rose 
  

   above 
  tree 
  level. 
  Frost 
  and 
  finally 
  ice 
  acted 
  vigorously 
  

   on 
  the 
  bare 
  rock 
  surfaces 
  and 
  pebbles. 
  The 
  streams 
  

   were 
  now 
  strong 
  enough 
  to 
  sweep 
  the 
  detached 
  frag- 
  

   ments 
  out 
  of 
  the 
  plain 
  where 
  they 
  formed 
  the 
  deposit 
  

   now 
  preserved 
  as 
  the 
  Dighton 
  conglomerate. 
  The 
  finer 
  

   material 
  was 
  carried 
  farther 
  from 
  the 
  mountains 
  and 
  

   may 
  have 
  formed 
  the 
  Carboniferous 
  rocks 
  of 
  central 
  

   Massachusetts. 
  

  

  Here 
  our 
  record 
  ends 
  for 
  the 
  Narragansett 
  Basin, 
  but 
  

   to 
  the 
  north, 
  in 
  the 
  Boston 
  Basin, 
  the 
  glaciers 
  reached 
  

   the 
  piedmont 
  slope 
  and 
  deposited 
  one 
  or 
  more 
  beds 
  of 
  

   till. 
  These 
  were 
  apparently 
  replaced 
  in 
  turn, 
  as 
  the 
  ice 
  

   retreated, 
  by 
  lakes 
  and 
  flats 
  in 
  which 
  beds 
  of 
  fine 
  mud 
  

   were 
  deposited. 
  

  

  The 
  history 
  of 
  the 
  Narragansett 
  Basin 
  is 
  the 
  history 
  

   of 
  one 
  of 
  the 
  mountain 
  and 
  climatic 
  movements 
  which 
  

   led 
  to 
  the 
  final 
  great 
  up-folding 
  of 
  the 
  Appalachian 
  

   revolution. 
  In 
  the 
  Devonian 
  delta 
  of 
  Pennsylvania 
  we 
  

   have 
  the 
  record 
  of 
  one 
  of 
  the 
  earlier 
  preparatory 
  move- 
  

   ments. 
  9 
  In 
  the 
  remains 
  of 
  the 
  piedmont 
  of 
  Rhode 
  Island 
  

   we 
  have 
  the 
  record 
  of 
  one 
  of 
  the 
  last 
  of 
  the 
  great 
  up- 
  

   heavals 
  which 
  finally 
  ended 
  the 
  history 
  of 
  Appalachia. 
  

  

  It 
  is 
  to 
  the 
  last 
  of 
  these 
  upheavals 
  that 
  we 
  owe 
  our 
  

   knowledge 
  of 
  the 
  Dighton 
  conglomerate 
  and 
  its 
  history. 
  

   For 
  although 
  Appalachia 
  itself 
  passed 
  away 
  v 
  along 
  with 
  

   most 
  of 
  its 
  piedmont, 
  four 
  great 
  masses 
  of 
  the 
  gravels 
  

   were 
  folded 
  far 
  below 
  the 
  surface 
  and 
  there 
  preserved. 
  

   Subsequent 
  erosion 
  has 
  revealed 
  them 
  to 
  us 
  as 
  the 
  New- 
  

   port 
  areas, 
  and 
  the 
  Dighton, 
  Taunton, 
  and 
  Attleboro 
  

   synclines. 
  

  

  Ehode 
  Island 
  State 
  College. 
  

   August, 
  1919. 
  

  

  9 
  Barrell, 
  J., 
  The 
  Upper 
  Devonian 
  Delta 
  of 
  the 
  Appalachian 
  Geosyncline, 
  

   'this 
  Journal 
  (4), 
  36, 
  429-472, 
  1913; 
  37, 
  87-109, 
  225-253, 
  1914. 
  

  

  