OF LAKE AREA OF WESTERN CANADA. 223 
common term. As the point is of much interest, however, it should 
be kept in view. 
4. Above the lower clay deposits, or resting immediately (where 
these are absent; on the foundation rock of the country, we meet 
with a series of sands and gravels of evidently northern origin, con- 
taining boulders of gneissoid and other rock, and alternating occa- 
sionally with beds of clay, in which northern boulders are also fre- 
quently found. This clay, with scarcely an exception, is remarkably 
free from calcareous matter,—the cause of which will be alluded to 
further on. In some places the clay and gravel are mixed up to- 
gether, and present no signs of stratification; but more usually 
they are distinctly stratified, and the boulders are mostly accumu- 
lated towards the upper part of the series. As a general rule, in- 
deed, the boulders occur in by far the greatest abundance, scattered, 
per se, over the surface of the gravels; or resting immediately on the 
underlying rocks where the clays and gravels are absent. This ap- 
pears to have arisen, in some cases, from the subsequent removal, or 
washing away, of the looser materials in which the boulders were 
originally imbedded ; but the greater number of these were evidently 
thrown down where they now lie, by melting or stranded icebergs, 
after the deposition of the other Drift materials. The boulders, 
whether of gneissoid or fossiliferous rock, belong always to northern 
localities, in relation to the spots on which they now occur. Here 
and there, the infiltration of water containing bi-carbonate of lime, 
has cemented some of these upper Drift deposits into conglomerates 
of considerable solidity. (Burlington Heights; vicinity of Niagara 
Falls ; Georgetown, &c.) 
5. Under the gravels and sands, or where the isolated boulders of 
this series are found, the rocks are always more or less marked by 
glacial action. ‘The more common effects comprise: a smoothed and 
polished surface, and a fine striation—the striz running in long 
straight lines in a general N.E. and 8. W. direction, although follow- 
ing to a certain extent, in hilly and broken districts, the natural 
windings of the rock slopes on which they occur. These effects are 
seen in Western Canada, at various heights above the sea-level, up 
to an elevation of at least 1500 feet. They are well shown on the 
top of the Collingwood escarpment, at about 1000 feet above the 
level of Lake Huron; on the same line of escarpment near Niagara 
Falls; on many of the rock exposures on the north shore of Lake 
