Geology of the Valley of the St. Lawrence, §c. 315 
= 
ley of St. David’s, about th 
valley appears to have beet u 
where it reaches the great escarpment at St. David’s, and between two 
and three hundred yards wide at the other end, or at the Whirlpool. 
Its steep sides did not consist of single precipices, as in the ravine of 
Niagara, but of suecessive cliffs and ledges. After its denudation the 
valley appears to have been submerged and filled up with sand, gravel, 
and boulder clay, three hundred feet thick. 
A description is next given of certain modern deposits, containing 
fresh-water shells, on the western borders of the Niagara, above the 
Falls, and in Grand Island, in order to show that the future recession 
of the Falls may expose patches of fluviatile sediment similar to those 
in and below Goat Island. 
The author then passes to the general consideration of the boulder 
formation on the borders of Lakes Erie and Ontario, and in the valley 
of the St. Lawrence, as far down as Quebec. Marine shells were ob- 
served in this drift at Beauport, below Quebec, as first pointed out by 
Captain Bayfield, and also near the mouth of the Jacques Cartier river, 
and at Port Neuf and other places; also at Montreal, where they reach 
a height probably exceeding five hundred feet above the sea, the sum- 
mit of Montreal mountain being seven hundred and sixty feet high, ac- 
cording to Bayfield’s trigonometrical measurement, and the shells being 
_ Supposed to be two hundred and forty feet below the summit. These 
shells, therefore, being more than three hundred feet above Lake On- 
tario, we may presume that the sea in which the drift was formed ex- 
tended far over the territery bordering on that lake. The most south- 
ern point at which the author saw fossil shells belonging to the same 
group as those of Quebec was on the western and eastern shores of 
Lake Champlain, viz. at Port Kent and Burlington, in about lat. 44° 
30’. Here, and wherever elsewhere the contact of the drift is seen 
with hard subjacent rocks, these rocks are smoothed, and furrowed on 
the surface, in the same manner as beneath the drift in northern Eu- 
Tope. The species of shells occurring in the drift, to which Mr. Lyell 
has made some additions, are not numerous, and are all, save one, 
known to exist, but are inhabitants, for the most part, of seas in higher 
latitudes. Many of them are the same as those occurring fossil at Ud- 
devalla and other places in Scandinavia, and they imply the former 
prevalence of a colder climate when the drift originated. At Beauport 
there are large and far-transported boulders, both in beds which overlie 
and underlie these marine shells. 
_ The author next describes the ridges of sand and gravel surrounding 
the great lakes, which are regarded by many as upraised beaches. He 
