﻿112 
  R. 
  R. 
  Hice 
  — 
  Inner 
  Gorge 
  Terraces 
  of 
  the 
  

  

  Akt. 
  XI. 
  — 
  The 
  Inner 
  Gorge 
  Terraces 
  of 
  the 
  Ujpper 
  Ohio 
  

   and 
  Beaver 
  Rivers 
  ; 
  by 
  R. 
  E. 
  Hice. 
  

  

  In 
  all 
  discussions 
  of 
  the 
  terraces 
  of 
  the 
  upper 
  Ohio 
  region 
  a 
  

   sharp 
  distinction 
  has 
  been 
  drawn 
  between 
  the 
  Upper 
  Rock 
  

   benches, 
  and 
  the 
  terraces 
  lining 
  the 
  inner 
  gorge, 
  first, 
  in 
  the 
  

   character 
  of 
  the 
  alluvium 
  connected 
  with 
  each 
  and, 
  secondly, 
  

   in 
  their 
  structure. 
  

  

  The 
  alluvium 
  of 
  the 
  Upper 
  Rock 
  bench 
  on 
  the 
  Beaver 
  river 
  

   (below 
  the 
  glacial 
  boundary), 
  consists 
  of 
  clayey 
  deposits, 
  with 
  

   occasional 
  pockets 
  of 
  gravel. 
  On 
  the 
  Ohio, 
  above 
  the 
  mouth 
  

   of 
  the 
  Beaver, 
  the 
  proportion 
  of 
  gravel 
  is 
  greater, 
  but 
  below 
  

   that 
  stream 
  the 
  deposits 
  partake 
  more 
  of 
  the 
  clayey 
  character, 
  

   reaching 
  however 
  a 
  much 
  greater 
  thickness 
  than 
  is 
  generally 
  

   found 
  on 
  the 
  Beaver. 
  

  

  The 
  alluvium 
  of 
  the 
  inner 
  terraces, 
  on 
  the 
  contrary, 
  is 
  

   almost 
  entirely 
  gravel, 
  with 
  a 
  large 
  proportion 
  of 
  metamorphic 
  

   material, 
  with 
  its 
  immediate 
  origin 
  in 
  the 
  morainic 
  deposits 
  a 
  

   few 
  miles 
  northward. 
  It 
  cannot 
  be 
  mistaken 
  for, 
  or 
  confused 
  

   with, 
  the 
  gravels 
  found 
  on 
  the 
  higher 
  benches, 
  from 
  which 
  it 
  

   is 
  distinguished 
  (1) 
  in 
  the 
  character 
  of 
  its 
  deposition, 
  (2) 
  in 
  

   the 
  proportion 
  of 
  metamorphic 
  material, 
  (3) 
  in 
  the 
  shape 
  of 
  

   the 
  pebbles, 
  (4) 
  in 
  the 
  apparent 
  greater 
  age 
  of 
  the 
  higher 
  

   gravels. 
  These 
  distinctions 
  when 
  once 
  noted 
  are 
  not 
  easily 
  

   mistaken, 
  and 
  taken 
  together 
  form 
  a 
  certain 
  guide, 
  irrespect- 
  

   ive 
  of 
  difference 
  in 
  elevation 
  above 
  present 
  stream 
  level. 
  

  

  The 
  distinguishing 
  feature 
  of 
  the 
  upper 
  terraces 
  is 
  the 
  ever 
  

   present 
  rock 
  shelf. 
  Prof. 
  White 
  in 
  speaking 
  of 
  the 
  most 
  

   prominent 
  of 
  the 
  upper 
  terraces 
  says 
  a 
  rocky 
  escarpment 
  leads 
  

   up 
  to 
  at 
  every 
  point 
  where 
  it 
  is 
  seen.* 
  In 
  point 
  of 
  fact, 
  the 
  

   true 
  character 
  of 
  the 
  upper 
  terraces 
  has 
  been 
  generally 
  recog- 
  

   nized, 
  in 
  that 
  they 
  represent 
  fragments 
  of 
  the 
  bed 
  of 
  the 
  

   stream, 
  left 
  in 
  the 
  original 
  excavation 
  of 
  the 
  valley. 
  They 
  are 
  

   thus 
  the 
  earliest 
  records 
  we 
  have 
  of 
  the 
  cutting 
  stream, 
  and 
  

   evidence 
  has 
  been 
  heretofore 
  presented, 
  both 
  of 
  a 
  general 
  and 
  

   local 
  character, 
  to 
  show 
  that 
  the 
  original 
  stream 
  flowed 
  to 
  the 
  

   north, 
  and 
  has 
  been 
  reversed. 
  

  

  On 
  the 
  other 
  hand, 
  it 
  has 
  been 
  assumed 
  heretofore, 
  that 
  the 
  

   distinctive 
  mark 
  of 
  the 
  terraces 
  of 
  the 
  inner 
  gorge 
  was 
  the 
  

   absence 
  of 
  any 
  included 
  rock 
  shelf. 
  This 
  assumption 
  presup- 
  

   poses 
  that 
  the 
  inner 
  gorge 
  differs 
  from 
  the 
  upper, 
  wider, 
  and 
  

   older 
  valley, 
  in 
  its 
  freedom 
  from 
  any 
  remnantal 
  benches, 
  and 
  

   from 
  their 
  supposed 
  absence 
  it 
  has, 
  in 
  turn, 
  been 
  assumed 
  that 
  

   the 
  cutting 
  of 
  the 
  inner 
  gorge 
  was 
  a 
  short, 
  quick, 
  continuous 
  

  

  * 
  For 
  principal 
  papers 
  relating 
  to 
  subject, 
  see 
  list 
  at 
  close 
  of 
  paper. 
  

  

  