﻿Spencer 
  — 
  Origin 
  and 
  Age 
  of 
  the 
  Ontario 
  Shore-Line. 
  359 
  

  

  region 
  the 
  approximate 
  age 
  of 
  the 
  

   Ontario 
  Beach 
  is 
  determinable. 
  

   Between 
  these 
  two 
  points, 
  the 
  en- 
  

   croachment 
  of 
  the 
  lake 
  has 
  been 
  

   measured 
  along 
  18 
  lines 
  coordinate 
  

   to 
  the 
  lake 
  shore. 
  These 
  points* 
  

   are 
  indicated 
  on 
  the 
  map 
  (fig. 
  4). 
  

   The 
  recession 
  of 
  the 
  two 
  terminal 
  

   points 
  has 
  been 
  unimportant 
  (re- 
  

   spectively 
  8 
  and 
  3 
  feet 
  in 
  50 
  years), 
  

   but 
  between 
  them 
  the 
  mean 
  lake 
  

   encroachment 
  has 
  been 
  2 
  feet 
  a 
  

   year. 
  

  

  The 
  total 
  recession 
  of 
  Scarboro 
  

   bluffs, 
  since 
  the 
  establishment 
  of 
  

   the 
  Ontario 
  Beach, 
  is 
  determinable 
  

   from 
  the 
  topography. 
  While 
  the 
  

   bluffs 
  reach 
  to 
  350 
  feet 
  above 
  the 
  

   lake, 
  the 
  Iroquois 
  terrace 
  skirts 
  

   their 
  face 
  except 
  for 
  less 
  than 
  half 
  

   a 
  mile, 
  where 
  it 
  has 
  been 
  under- 
  

   mined 
  by 
  the 
  waves 
  (see 
  fig. 
  4). 
  

   This 
  shows 
  that 
  the 
  post-Iroquois 
  

   surface, 
  removed 
  by 
  the 
  lake, 
  rose 
  

   less 
  than 
  200 
  feet 
  above 
  it, 
  and 
  its 
  

   slope 
  should 
  correspond 
  to 
  that 
  of 
  

   the 
  country 
  between 
  the 
  Iroquois 
  

   Beach 
  and 
  the 
  low 
  shore, 
  just 
  west 
  

   of 
  Victoria 
  Park, 
  a 
  distance 
  of 
  

   4,000-4,400 
  feet. 
  Such 
  would 
  in- 
  

   dicate 
  the 
  original 
  extension 
  of 
  the 
  

   Ontario 
  shore 
  in 
  front 
  of 
  Scarboro 
  

   Bluffs. 
  

  

  This 
  location 
  is 
  confirmed 
  by 
  the 
  

   restoration 
  of 
  the 
  natural 
  shore-line 
  

   in 
  front 
  of 
  the 
  indentation 
  in 
  the 
  

   bluffs 
  (see 
  figs. 
  1 
  and 
  4), 
  where 
  

   their 
  truncation 
  represents 
  the 
  

   recession 
  of 
  the 
  original 
  Ontario 
  

   shore. 
  Combining 
  the 
  mean 
  rate 
  

   of 
  recession 
  of 
  2 
  feet 
  a 
  year 
  with 
  

   the 
  amount 
  of 
  encroachment 
  deter- 
  

   mined, 
  the 
  age 
  of 
  the 
  Ontario 
  

   Beach 
  is 
  found 
  to 
  be 
  approximated 
  

   2,000 
  years. 
  

  

  * 
  Mr. 
  F.M. 
  Passinore 
  marked 
  by 
  18 
  corner- 
  

   stones 
  the 
  position 
  of 
  the 
  bluffs 
  in 
  1882-3. 
  

   Messrs. 
  Speight 
  and 
  Van 
  Nostrand 
  re-sur- 
  

   veyed 
  them 
  in 
  1912 
  (for 
  the 
  Toronto 
  Water 
  

   Supply). 
  By 
  comparison 
  of 
  these 
  surveys 
  

   the 
  mean 
  recession 
  has 
  been 
  found. 
  

  

  Fig. 
  4. 
  

  

  

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  Fig. 
  4. 
  Map 
  showing 
  Scar- 
  

   boro 
  Bluffs, 
  Iroquois 
  Beach 
  

   and 
  later 
  encroachments 
  on 
  

   the 
  shore. 
  

  

  Am. 
  Jour. 
  Sci.— 
  Fourth 
  Series, 
  Vol. 
  XLIII, 
  No. 
  257.— 
  May, 
  1917. 
  

   25 
  

  

  