——-- 
Toronto Interglacial Period.—Coleman., 73 
the last ten years, since careful observations have been made 
of the Don and Humber, these two streams have not appre- 
ciably deepened their channels when running through the 
shale. One hundred years is therefore a small allowance 
for 16 feet of cutting. 
At the very bottom of the Don warm climate beds there 
is a thick mat of deciduous leaves with branches and trunks of 
trees, etc.; and layers with wood and leaves occur at several 
levels above this, separated by beds of stratified clay and sand. 
Unfortunately most of the wood is greatly compressed so 
that the annual rings cannot be counted, but some of the logs 
found were more than 18 inches across. My best specimen, 
a section of wood a little less than 4 inches across, shows 120 
annual rings. From their curvature it is evident that the 
complete trunk was at least 7 inches in radius, so that the 
tree must have been about 200 years old. Probably some of 
the larger logs belonged to trees of much greater age. We 
must assume therefore that the ice had retreated more than 
200 years before the warm climate beds began to form; for the 
logs at their base must have grown somewhere to the north, 
so as to have been undermined and brought down by the 
stream. How many successive generations of forest trees are 
represented in the higher beds containing wood and deciduous 
leaves is uncertain, but it is surely safe to assume that two 
generations matured, requiring at least 400 years. 
The peaty clays often show fine lamination with thin silty 
layers at intervals of 1% or 2 inches, the latter often charged 
with spruce needles, beetles’ wings, etc. These peaty layers 
are not always distinct, and there are beds of the clay 2 or 3 feet 
thick which do not show them, the peaty and silty matter being 
more or less mixed with the clay in these parts. It is natural 
to assume that the silty layers are of an annual character, and 
if we reckon that two inches of clay were deposited annually 
over the delta, which was 18% inches wide, the 94 feet re- 
quired 564 years to form. 
How long the 55 feet of overlying stratified sand needed 
for their formation is hard to guess, but half a foot a year 
seems as rapid a rate of deposit as one can assume for so 
wide a delta. This would give 110 years for the in- 
terglacial sands. The shortest time admissible for the growth 
