
GLACIAL PHENOMENA AND SUPERFICIAL DEPOSITS. 211 
bution of the limestone debris appear to offer. Icebergs, at some time 
during the glacial period, may have passed southward over the Lauren- 
tian watershed to the north-east, bearing with them fragments from the 
limestone formations of Hudson’s Bay. In this case, it would be neces- 
sary alsg *to suppose a subsequent developement of glaciers on the 
watershed itself, sufficient to remove this older debris to the south, 
as indicated by its position; and there is no sign of a heaping up of 
moraine matter, such as might be expected under these circumstances. 
It is also possible, that at a certain period of submergence of the region, 
ice may have floated eastward, over what is now an expanse of drift and 
detritus, and carried blocks from the Red River and Winnipeg districts, 
where, though no beds of Upper Silurian age are yet known, rocks of 
the Lower Silurian and Devonian are found. This appears to be the 
more probable supposition, as other evidence seems also to point in the 
direction of a south-eastern drift in this region, toward the close of the 
glacial period. Whether, however, it be conceded or not, that the lime- 
stone fragments of the southern part of the lake, are derived from lime- 
stone immediately underlying, it is probable from the general contour of 
the region, that Silurian or Devonian rocks overlap the older formations 
about this place. 
479. The boulders of the northern part of the lake, are exclusively 
derived from Laureutian and Huronion rocks. They are generally accu- 
mulated on the south sides of the islands, which are apt to show bare 
rocky shores to the north. The same is true on a greater scale, with 
regard to their distribution in the region generally, the northern shore 
of Sand-hill Lake, being much encumbered with boulders. About thirty 
miles eastward from the North-west Angle, where the shore is sheltered, 
occasional patches of an old terrace, ten to fifteen feet above the 
present water-level of the lake, are seen both on the main shore, and on 
the southern ends of islands. It is composed of gravel and small 
boulders, and may probably be the littoral representative of the 
terraces of clay and finer material occurring in the south. A clay quite 
similar to that seen in the southern part of the lake, appears underlying 
several feet of sand, in a deep ditch at the side of the Winnipeg Road, a 
few miles from the North-west Angle, and not far above the level of the 
lake. It is rather hard, yellowish-grey in colour, thin-bedded, and mingled 
with very fine sand. The boulders and erratic blocks of Clear-water 
Lake, are also entirely Laurentian and Huronian ; granite, gneiss, diorite, 
eS 
and greenstone conglomerate being most abundant, 
