﻿Upper 
  Ohio 
  and 
  Beaver 
  Rivers. 
  117 
  

  

  greater 
  or 
  less 
  extent. 
  The 
  first 
  four, 
  and 
  those 
  of 
  Monaca, 
  

   Aliquippa 
  and 
  Shannopin 
  are 
  not 
  favorably 
  situated 
  to 
  show 
  

   the 
  presence 
  of 
  an 
  included 
  rock 
  shelf; 
  no 
  stream 
  cutting 
  

   them 
  in 
  such 
  a 
  way 
  as 
  to 
  reveal 
  their 
  structure. 
  

  

  It 
  has 
  not 
  been 
  possible 
  in 
  all 
  cases 
  to 
  assign 
  even 
  approxi- 
  

   mate 
  limits 
  to 
  the 
  observed 
  rock 
  benches. 
  At 
  Raccoon, 
  Bea- 
  

   ver, 
  Rochester 
  and 
  Economy 
  it 
  is 
  evident 
  they 
  underlie 
  but 
  a 
  

   portion 
  of 
  the 
  terrace 
  and 
  there 
  is 
  as 
  yet 
  no 
  data 
  that 
  will 
  

   enable 
  any 
  estimate 
  of 
  proportion 
  of 
  included 
  rock 
  shelf 
  to 
  

   entire 
  terrace 
  to 
  be 
  made. 
  At 
  New 
  Brighton 
  the 
  rock 
  extends 
  

   only 
  under 
  the 
  lower 
  terrace, 
  and 
  whether 
  it 
  underlies 
  more 
  

   than 
  that 
  portion 
  of 
  the 
  terrace 
  lying 
  between 
  the 
  buried 
  and 
  

   modern 
  channels 
  of 
  the 
  river 
  has 
  not 
  yet 
  been 
  determined. 
  At 
  

   Beaver 
  Falls 
  the 
  limits 
  of 
  the 
  rock 
  are 
  well 
  defined, 
  and 
  esti- 
  

   mating 
  from 
  the 
  bottom 
  of 
  the 
  buried 
  channel, 
  one-half 
  of 
  the 
  

   whole 
  terrace 
  would 
  seem 
  to 
  be 
  rock. 
  At 
  Eastdale 
  the 
  rock 
  

   rises 
  practically 
  to 
  the 
  surface, 
  and 
  fully 
  nine-tenths 
  of 
  this 
  

   fragment 
  is 
  rock. 
  At 
  Homewood 
  the 
  rock 
  underlies 
  the 
  whole 
  

   of 
  the 
  gravel 
  deposit 
  and 
  constitutes 
  one-half 
  of 
  the 
  whole 
  (the 
  

   gravel 
  here 
  rising 
  to 
  the 
  level 
  of 
  the 
  outer 
  rock 
  bench). 
  At 
  

   Wampum 
  the 
  greater 
  portion 
  of 
  the 
  terrace 
  seems 
  to 
  be 
  rock. 
  

   The 
  shelf 
  shows 
  for 
  some 
  distance 
  along 
  the 
  river 
  front 
  and 
  

   rises 
  almost 
  to 
  the 
  level 
  of 
  the 
  terrace, 
  which 
  is 
  also 
  true 
  at 
  

   Moravia. 
  In 
  the 
  terrace 
  extending 
  from 
  Baden 
  to 
  Legionville 
  

   the 
  railroad 
  cutting 
  shows 
  rock 
  reaching 
  practically 
  to 
  the 
  surface 
  

   and 
  constituting 
  at 
  least 
  four-fifths 
  of 
  the 
  entire 
  terrace. 
  

  

  It 
  will 
  thus 
  be 
  seen 
  that 
  the 
  data 
  for 
  forming 
  an 
  estimate 
  is 
  

   not 
  sufficient 
  to 
  judge 
  accurately, 
  yet 
  it 
  must 
  be 
  evident 
  that 
  

   the 
  included 
  rock 
  benches 
  form 
  no 
  insignificant 
  portion 
  of 
  the 
  

   inner 
  terraces, 
  and 
  reduces 
  by 
  that 
  amount 
  the 
  immense 
  quan- 
  

   tity 
  of 
  alluvium 
  which 
  it 
  has 
  been 
  supposed 
  made 
  up 
  the 
  ter- 
  

   races. 
  From 
  the 
  present 
  data 
  the 
  writer 
  believes 
  the 
  propor- 
  

   tion 
  of 
  rock 
  will 
  be 
  found 
  over, 
  rather 
  than 
  under, 
  one-half 
  of 
  

   the 
  entire 
  volume 
  of 
  the 
  terraces, 
  measured 
  from 
  the 
  bottom 
  of 
  

   the 
  buried 
  channel. 
  

  

  The 
  attempt 
  to 
  correlate 
  the 
  rock 
  benches 
  has 
  not 
  been 
  

   entirely 
  satisfactory. 
  Taken 
  as 
  a 
  whole 
  the 
  benches 
  on 
  the 
  

   Beaver 
  (Moravia, 
  Wampum, 
  Homewood, 
  Eastdale, 
  Beaver 
  

   Falls, 
  New 
  Brighton) 
  lie 
  at 
  about 
  the 
  same 
  elevation 
  above 
  

   present 
  stream 
  level 
  (30' 
  to 
  40'). 
  The 
  benches 
  on 
  the 
  Ohio 
  

   (Economy, 
  Baden, 
  Rochester, 
  Beaver, 
  Raccoon) 
  lie 
  at 
  a 
  some- 
  

   what 
  higher 
  elevation 
  above 
  stream 
  level 
  (50'db), 
  yet 
  it 
  seems 
  

   they 
  belong 
  to 
  the 
  same 
  series 
  found 
  on 
  the 
  Beaver. 
  The 
  

   Ohio 
  is 
  flowing 
  over 
  its 
  buried 
  channel 
  in 
  this 
  region 
  and 
  has 
  

   eroded 
  its 
  post-terrace 
  channel 
  deeper 
  than 
  the 
  Beaver, 
  which 
  

   has 
  been 
  cutting 
  a 
  new 
  rock 
  channel 
  within 
  about 
  two 
  miles 
  of 
  

   its 
  mouth, 
  and 
  that 
  through 
  the 
  hard 
  Homewood 
  sandstone. 
  

  

  