﻿E. 
  H. 
  Perkins 
  — 
  DigMon 
  Conglomerate. 
  71 
  

  

  that 
  there 
  is 
  a 
  certain 
  amount 
  of 
  that 
  element 
  in 
  the 
  

   rocks. 
  The 
  light 
  colors 
  therefore 
  indicate 
  that 
  the 
  iron 
  

   is 
  in 
  the 
  f 
  errons 
  form. 
  In 
  the 
  neighborhood 
  of 
  the 
  coaly 
  

   shales 
  this 
  may 
  be 
  due 
  to 
  reduction 
  by 
  organic 
  matter. 
  

   However, 
  the 
  same 
  light 
  color 
  persists 
  through 
  great 
  

   thicknesses 
  of 
  rock 
  which 
  have 
  no 
  carbonaceous 
  beds 
  in 
  

   their 
  immediate 
  vicinity. 
  It 
  seems 
  most 
  likely 
  that 
  the 
  

   material 
  of 
  the 
  formation 
  was 
  eroded 
  and 
  deposited 
  

   under 
  conditions 
  which 
  did 
  not 
  permit 
  the 
  oxidation 
  and 
  

   dehydration 
  of 
  the 
  iron. 
  Plenty 
  of 
  ground-water 
  would 
  

   perhaps 
  be 
  the 
  most 
  efficient 
  agent 
  for 
  such 
  work. 
  The 
  

   water 
  would 
  fill 
  the 
  pore 
  spaces 
  in 
  the 
  loose 
  unconsoli- 
  

   dated 
  material, 
  keeping 
  out 
  atmospheric 
  oxygen 
  and 
  at 
  

   the 
  same 
  time 
  making 
  drying 
  of 
  the 
  deposits 
  a 
  slow 
  pro- 
  

   cess. 
  In 
  warm 
  moist 
  climates 
  where 
  chemical 
  action 
  is 
  

   rapid, 
  red 
  deposits 
  are 
  now 
  being 
  made. 
  The 
  blues 
  and 
  

   grays 
  of 
  the 
  Dighton 
  beds 
  are, 
  then, 
  an 
  indication 
  of 
  a 
  

   moist 
  cool 
  climate. 
  

  

  Fossils. 
  

  

  No 
  marine 
  fossils 
  have 
  been 
  found 
  in 
  the 
  rocks 
  of 
  the 
  

   Narragansett 
  Basin. 
  Vegetable 
  forms 
  are 
  dominant, 
  a 
  

   list 
  of 
  twenty-six 
  species, 
  mainly 
  from 
  Pawtucket, 
  and 
  

   identified 
  by 
  Leo 
  Lesquereux, 
  being 
  given 
  by 
  Wood- 
  

   worth. 
  7 
  This 
  flora 
  is 
  equivalent 
  to 
  that 
  of 
  the 
  Upper 
  

   Carboniferous 
  in 
  Pennsylvania. 
  As 
  the 
  beds 
  in 
  which 
  

   the 
  plants 
  were 
  found 
  represent 
  the 
  lower 
  half 
  of 
  the 
  

   Coal 
  Measures, 
  there 
  is 
  nothing 
  in 
  this 
  evidence 
  to 
  pre- 
  

   vent 
  placing 
  the 
  Dighton 
  conglomerate 
  several 
  thousand 
  

   feet 
  higher 
  up 
  in 
  the 
  Permian. 
  The 
  same 
  beds 
  which 
  

   yield 
  the 
  flora 
  mentioned 
  have 
  given 
  fourteen 
  species 
  of 
  

   insects. 
  8 
  These, 
  with 
  "the 
  impression 
  of 
  an 
  annelid 
  

   worm, 
  several 
  shells 
  of 
  Spirorbis, 
  and 
  what 
  appears 
  to 
  

   be 
  the 
  track 
  of 
  a 
  gastropod 
  mollusk" 
  are 
  the 
  only 
  traces 
  

   of 
  animal 
  life 
  which 
  have 
  been 
  found 
  in 
  the 
  basin. 
  

  

  Associated 
  Sediments. 
  

  

  The 
  sediments 
  associated 
  with 
  the 
  Dighton 
  conglom- 
  

   erate 
  consist 
  of 
  arkoses, 
  conglomerates, 
  sandstones, 
  

   shales, 
  coal 
  and 
  graphite 
  beds 
  and 
  carbonaceous 
  shales. 
  

   The 
  series 
  starts 
  with 
  a 
  basal 
  arkose, 
  lying 
  between 
  the 
  

  

  7 
  Shaler, 
  N. 
  S., 
  Woodworth, 
  J. 
  B., 
  and 
  Foerste, 
  A. 
  F., 
  op. 
  cit. 
  p. 
  204. 
  

  

  8 
  Op. 
  cit, 
  p. 
  202. 
  

  

  