﻿Plate 
  7 
  

  

  Cliff 
  on 
  the 
  Canadian 
  side 
  of 
  the 
  gorge, 
  showing 
  the 
  receding 
  base. 
  The 
  giaat 
  

   icicle 
  marks 
  the 
  edge 
  of 
  the 
  overhanging 
  ledge 
  (Copyright 
  by 
  Underwood 
  & 
  

   Underwood, 
  New 
  York) 
  

  

  