642 THE JOURNAL OF GEOLOGY. 
descence of glacial conditions after another interval, is indicated 
by the great morainic loops stretching from Trenton westwards 
to Lake Huron and passing (as the Oak ridges) about eighteen 
miles north of Toronto. 
The post-glacial history of the region near Toronto has not 
yet been satisfactorily worked out, though one episode, that of 
the Iroquois water as described by Dr. Spencer, has left its mark 
very distinctly in the old beach to the north of the city, and 
must have had considerable importance as regards the formation 
of surface deposits. 
Much of the somewhat loess-like fine clayey sands of the 
Humber valley may turn out to be post-glacial; and Dr. Hinde 
supposes that the upper hundred feet of sand and gravel at the 
west end of the Scarboro’ cliffs are of the same age; but my 
own observations incline towards an inter-glacial position for 
these thick and widespread but greatly eroded deposits. Similar 
sands occurring at York Mills and other points north of the city 
are undoubtedly covered by the upper till, which may simply 
have been removed from the more southern parts near the lake. 
Unprotected by a layer of till these sands are easily attacked by 
wind and water and superficially rearranged, so that their original 
structure and relationship becomes obscured. 
Of course the Don and Humber with their tributaries have 
formed in the lower sluggish parts of their courses alluvial 
deposits of clay and sand that are evidently modern, and in some 
instances are added to by every spring flood. 
The succession of events since Pliocene times in the vicinity 
of Toronto may now be reviewed in order to bring to a focus the 
results of the observations described in this paper. 
No Pliocene deposits have been found in this region, suppos- 
ing the earliest advance of the ice to indicate the end of the 
Pliocene; but the lowest till forms a carpet over the eroded 
surface of the Hudson River shales. At the time the earliest 
glacier advanced the Scarboro’ region formed a valley whose 
hollow is now below the surface of Lake Ontario, and there were 
low hills where the Don and Humber valleys now exist, the 
