﻿212 
  GEOLOGY. 
  

  

  This 
  is 
  still 
  more 
  satisfactorily 
  exhibited 
  in 
  the 
  deeply- 
  

   cut 
  channels 
  of 
  rivers 
  running 
  in 
  a 
  direction 
  transverse 
  

   from 
  that 
  of 
  the 
  strata 
  for 
  many 
  miles, 
  which 
  often 
  

   occurs, 
  by 
  which 
  the 
  whole 
  may 
  be 
  distinctly 
  brought 
  

   into 
  view, 
  in 
  regular 
  order, 
  as 
  represented 
  in 
  Plate 
  X., 
  

   Fig. 
  2. 
  This 
  is 
  well 
  exemplified 
  in 
  the 
  Niagara 
  River 
  

   1)elow 
  the 
  falls, 
  as 
  noticed 
  by 
  Mr. 
  Lyell. 
  

  

  Thus 
  it 
  is, 
  by 
  accumulating 
  and 
  collating 
  such 
  data, 
  

   derived 
  from 
  various 
  and 
  distant 
  quarters, 
  aided 
  also 
  by 
  

   the 
  chemical 
  composition 
  of 
  the 
  rocks 
  and 
  their 
  imbedded 
  

   fossils, 
  that 
  our 
  knowledge 
  of 
  the 
  structure 
  of 
  the 
  earth 
  

   is 
  acquired. 
  

  

  The 
  geological 
  structure 
  of 
  this 
  State 
  embraces 
  the 
  

   Quaternary 
  and 
  Tertiary 
  formations, 
  and 
  merely 
  enters 
  

   upon 
  the 
  higher 
  strata 
  of 
  the 
  Secondary, 
  including, 
  

   perhaps, 
  the 
  equivale7its 
  of 
  the 
  ma^stricht 
  beds, 
  and 
  to 
  a 
  

   limited 
  extent 
  those 
  of 
  the 
  Cretaceous 
  group. 
  

  

  The 
  name 
  of 
  this 
  group 
  is 
  derived 
  from 
  the 
  chalk 
  

   which, 
  in 
  Europe, 
  constitutes 
  its 
  prominent 
  feature. 
  Here 
  

   it 
  is 
  characterized 
  by 
  yellow, 
  ferruginous, 
  and 
  green 
  

   sands, 
  and 
  micaceous 
  shales, 
  associated 
  with 
  and 
  replaced 
  

   by 
  limestones, 
  approaching 
  to 
  a 
  chalky 
  aspect, 
  but 
  afford- 
  

   ing 
  neither 
  real 
  chalk 
  nor 
  flints. 
  

  

  Its 
  thickness 
  has 
  been 
  estimated 
  as 
  varying 
  from 
  three 
  

   hundred 
  to 
  six 
  hundred 
  feet. 
  

  

  Its 
  organic 
  remains 
  are 
  nearly 
  all 
  marine, 
  and 
  are 
  en- 
  

   tirely 
  distinct 
  from 
  those 
  of 
  the 
  Tertiary 
  above. 
  

  

  The 
  older 
  rocks 
  of 
  the 
  Secondary 
  and 
  those 
  of 
  the 
  

   Primary 
  formation 
  are 
  not 
  found 
  at 
  all 
  in 
  the 
  State, 
  ex- 
  

   cept 
  in 
  the 
  transported 
  fragmentary 
  pebbles 
  and 
  boulders 
  

   of 
  the 
  diluvium 
  or 
  northern 
  drift. 
  

  

  With 
  these 
  preliminary 
  explanations, 
  which 
  could 
  not 
  

   Ije 
  more 
  briefly 
  stated, 
  and 
  which, 
  however 
  familiar 
  to 
  

   many, 
  may 
  be 
  essential 
  to 
  a 
  general 
  understanding 
  of 
  

  

  