GEOLOGY OF THE WESTERN DISTRICTS OF CANADA. 511 
valley had originally existed, which, during the glacial period, was 
filied up with the materials peculiar to it. 
The average depth of the clay over the area comprised between 
the foot of the slope of the mountain and the lake shore seems to be 
about twelve feet; but at the artesian well at St. Catherines it is 
forty feet thick. There isa remarkable break in the continuity of the 
red marl of the Silurian formation, commencing at the eastern limits 
of Hamilton and terminating at the west side of the old canal; the 
intervening space being filled to an unknown depth with laminated 
clay aud sand. May not this be accounted for by the abrasion and 
grinding down of the older soft marl, produced by the agitation of the 
icebergs which I have supposed to be congregated and imprisoned in 
this locality? The clay has been pierced to a depth of from sixty to 
seventy feet at the passenger station of the Great Western Railway 
without passing through it. 
Succession of Changes.—I shall now in conclusion give a brief 
general retrospect of the probable succession of events which have 
produced the geographical and physical configuration of the region 
under notice. 
The first event to which we must recur is the successive deposition, 
at a time vastly and immeasurably remote, of the. stratified rocks 
shewn in these sections. I have said that they belong to the 
oldest fossiliferous rocks, and probably they contain the records of the 
first of living forms. That they are of marine origin is indisputable 
from the sea weeds and deep sea shells which they contain, but no 
trace of fishes, of vertebrated animals or of terrestrial vegetation 
can be discovered in them, and it seems to have been for many ages a 
creation of molluscs, corals and crustaceans. These rocks remained 
nearly undisturbed and horizontal from the era of their formation to 
a comparatively modern period, during which interval the whole of 
the geological formations subsequent to the Silurian system were 
deposited in different parts of the globe; and the vast succession of 
species of animals and plants whose histories we find written in these 
rocks have flourished and perished and been slowly entombed. 
During this interval also, and while the rocks in question still 
remained submerged in the ocean, they were denuded by currents, 
that is, portions were worn off and transported away, soas to form 
irregularities of surface, such as the basins of our great lakes, and 
