Toronto and Scarhoro' Drift Scries. — Uphain. 311 
tained from them. The stratified snnds were apparently laid down 
like the clays, from materials brought from the north by the Laurentian 
river, but in the shallower water where wave action was effective, 
forming wide sand flats and largely filling the western side of the bay 
previously described. 
A series of interglacial sands and gravels occurs in western Toronto, 
and is well exposed in large pits near Christie and Shaw streets ; but 
its exact relation to the Scarboro' deposits is not certain. Where the 
two series meet near the corner of Dupont and Bathurst streets there 
are two or three beds of clay with peaty layers interstratified with sand, 
suggesting that the sand and gravel are of the same age as the Scarboro' 
clay. 
The sand and gravel beds have a thickness of at least 78 feet, and 
rise 130 or 140 feet above lake Ontario, but their extent is unknown, as 
they are in general buried under boulder clay. It is certain that these 
beds were formed under different conditions from those either of the 
Don or Scarboro'. They are of coarser and more variable materials, 
often showing very marked cross bedding, probably produced by cur- 
rents rather than waves, and sometimes apparent unconformities such 
as are made by a stream changing its bed. We may suppose that an 
interglacial Humber river coming in from the west or northwest, 
brought down sand and gravel at the edge of the great bay, mingling 
them at some points with the clayey delta materials of the Laurentian 
river. 
This brings to a close the series of deposits forming the Toronto 
formation. In all there are four varieties, the sands and clays of the 
Don, with their warm climate trees and Mississippi Unios; the peaty 
clays of Scarboro', with their seventy distinct beetles and their small 
flora, suggesting a cool but not arctic climate; the stratified sands over- 
lying them, probably forming a continuation of the cool climate period ; 
and the western sands and gravels, with elephants, bisons, and some 
shell-fish, affording little evidence as to climate. The maximum thick- 
ness observed in each set of deposits is as follows : 
3. Scarboro' sands 60 feet.' 
2. Scarboro' peaty clays 94 feet. -ur .. . , 
I. Don beds 41 H feet, i 4- Western sands and grav- 
' els 78 feet. 
195^ feet. 
These Toronto and Scarboro' interglacial deposits, after 
being spread as a vast composite delta plain, with gentle lake- 
ward slope, were deeply channeled by several streams before 
the ensuing glaciation covered the whole with alternating 
sheets of till and modified drift. On the present shore these 
valleys, partially filled by the later drift, descend below the 
level of lake Ontario, showing that after the delta accumula- 
tion this part of the lake held for some time a lower level than 
now. 
