TORONTO GLACIAL AND INTER-GLACIAL DEPOSITS. 643 
highest observed level of the shale being about eighty feet above 
the lake at Lambton Mills on the Humber. 
The retreat of the ice was followed by a rise in the water of 
the lake to a level at least 150 feet above the present lake, 
depositing that depth of clay and sand upon the unweathered till. 
The Scarboro’ water, as it may perhaps be called, was then 
drained off to a point below the present lake level, and at some 
points erosion took place to a corresponding depth. It is possi- 
ble that the climate became warmer during this period of erosion 
and that the Don beds were deposited afterwards. 
At the time of the second glacial period the topography of 
the region had greatly changed. The Scarboro’ Heights already 
had an elevation of 150 feet, while valleys reaching the present 
lake level had been cut by Highland Creek and the Don, as well 
as by the Dutch Church stream, which now has no equivalent. 
The retreat of the second ice-sheet was followed by a rise of the 
water to a height of 280 feet above the present lake, the water 
being cold and lifeless, and bearing ice floes. 
Once more the lake was drained, at least partially, and erosion 
went on, for the upper till is found at a sand pit near the corner 
of Bloor and Christie streets in Toronto at a level of about 120 
feet above the present lake. Either the period of dry land was 
short, giving no time for the cutting of deep valleys, or the level 
of the lake of those days was considerably above the present 
Lake Ontario. The contour of the land at the end of this inter- 
glacial period is more difficult to settle than in the former one; 
but it is tolerably certain that the Scarboro’ Heights had almost 
their present height, and that the Don valley was much shallower 
than at present, if it existed at all. 
The retreat of the third ice-sheet was followed as before by a 
rise of water, Lake Iroquois reaching 160 feet above the present 
lake to the north of Toronto, and about 190 at Scarboro’. After 
the draining of Lake Iroquois it is probable that the surface of 
the country presented much the same rolling swells of till as are 
now found north and east of Toronto; for, in general, erosion 
has gone on to a moderate degree only, except where the more 
