10 
MUSEUM BULLETIN NO. 24. 
It occurs practically at all altitudes from 130 feet up to 600 feet. 
In the lower portions of the Ottawa valley it is generally finer 
grained and contains less silt and sand. In its upper portion the 
lower clay in places passes upward into sand. This occurs most 
markedly at altitudes from 200 up to 350 feet. In places, as 
along the Rideau river near Rideau junction, the sand overlying 
the lower silty clay is as much as 20 feet thick and is overlain 
by the upper clay. The sand is generally evenly bedded but 
often strongly ripple-marked. In the lower portion of the Ottawa 
valley near Ottawa the sand is generally thin or absent and the 
lower silty clay is overlain directly by the upper clay. The lower 
clay shows every evidence of the presence of floating ice. Glaci- 
ated stones and boulders occur abundantly in the lower portion 
of the clays and the beds in many places are crumpled and 
contorted as if by the grounding of icebergs. This is well seen 
in sections exposed along the shore of Lake Deschenes at the 
foot of Graham bay, at Black rapids on the Rideau river, and 
in the bed of the brook leading up to Kingsmere from the east. 
The contorted beds are in places overlain and underlain by 
undisturbed beds showing practically contemporaneous defor- 
mation. The lower silty and sandy clays form the greater portion 
of the marine sediments and there can be little doubt that they 
were derived from the waters of the melting ice-sheet which 
could not have been far distant when the clays were deposited. 
The upper clay overlies the lower sandy and silty clay at 
practically all altitudes from the lowest part of the Ottawa valley 
up to at least 425 feet. It is generally only 6 to 10 feet thick, 
but in places has a maximum thickness of 20 feet or possibly 
more. The upper clay differs markedly in physical character 
from the lower clay. It is an exceedingly fine-grained plastic 
clay generally interlaminated with sandy bands in its lower 
portion near the contact with the underlying sandy or silty 
beds, but becoming nearly free from sand in its upper portion. 
Boulders occur occasionally in and on the surface of the clays 
as If dropped from floating ice or ice-floes in the manner described 
by Hind, 1 but the upper clays are not known to be crumpled 
or disturbed except where landslides have occurred. The 
Canadian Monthly, Sept., 1875. 
