222 DRIFT DEPOSITS AND ANCIENT EXTENSION 
tions are spread, had been extensively denuded prior to their deposi-. 
tion upon it. They cover, thus, an undulating and more or less 
broken surface; and their thickness, consequently, apart from the 
denudation to which they have been themselves subjected, is exe 
ceedingly variable. 
2. The lowest of these deposits appear to consist of dark blue or 
greyish clays, with thin layers of yellowish or light-coloured clay in 
places. This deposit is often lamjnated horizontally, and is gener- 
ally very calcareous. It appears also to be free from northern or 
large crystalline boulders. Pebbles of limestone and other fossili- 
ferous rock, mixed with some small pebbles of water-worn gneiss, 
occur abundartly in it in many localities; but northern boulders, 
properly so-called, are either absent or exceedingly rare. Amongst 
. the localities in which these lower and boulder-free clay deposits are 
of marked occurrence, the district around Toronto, and many parts 
of the valley of the Saugeen and western shores of Lake Huron, 
may be especially mentioned; but wherever our drift deposits are 
found to consist of clay and other materials, the clay-beds are almost 
invariably seen to occupy the lower place. At the same time, as 
described more fully in the sequel, beds of yellow and other coloured 
clay, it should be observed, are occasionally found with northern 
boulders in a higher part of the series,—but these are quite distinct 
from the lower clays now referred to. They are, moreover, of no 
great thickness, but alternate with, and are subordinate to, thick 
deposits of gravel and sand; whereas, the lower clays attain in 
places to a thickness of over 100 feet, and present a general uni- 
formity throughout. In these latter beds, no traces of contempora- 
neous fossils have, as yet, been found. 
3. It is generally assumed, as an established fact, that the harder 
rocks beneath the Drift exhibit everywhere the marks of glacial 
action. Although we have numerous examples throughout this sec- 
tion of the Province, of polished and striated rock, I believe it to 
be still an open question as to whether the rocks which underlie 
these lower clays, have been thus affected. I have not been able to 
discover any instances of it, nor can I find any recorded cases in our 
Geological Reports, or in other trustworthy sources. The question, 
hitherto, does not seem to have been mooted,—the Drift accumula- 
tions, generally, being classed together by most observers under one 
