272 Canadian Record of Sctence. 
150 miles long and 24 miles broad, and in outline very like 
that of the present lake, but approaching the southern side 
within three to seven miles for the whole distance. The 
line of deepest depression along the length of the lake is 
also located about two-thirds of the way across the lake 
towards the New York State side. South of Port Credit 
and Toronto it takes the centre of the lake, but after that 
swerves towards the southern side. Preserving a depth of 
540 to 570 feet for over sixty miles, it reaches the 600-foot 
line area, and finally begins to shallow at about nine miles off 
Oswego, where the depth is 576 feet. The evidence afforded 
by the terraces on either side of Lake Ontario would appear 
to show that, on the elevation of the land to its present 
limit, the rise was greater towards the north ofthe lake than 
to the south. ‘This would cause the strata on the north side 
to dip towards the south, and force the waters of the lake 
more towards the southern side. 
The lake bottom within the 600-foot line is chiefly mud, 
whilst outside, within the 300-foot line, it is largely clay and 
mud, with sand in occasional places. Close to the southern 
and eastern shores, rock is met with for the whole distance, 
but, with one exception, not elsewhere. The only large con- 
nected stretches of sand occur off and to the north-east of 
Oswego, suggesting, though not necessarily, an old outlet 
there. 
Between Stony Point, off Sackett’s Harbor, and South Bay 
Point, on the Canadian side, there is a rise in the level of 
the lake floor, culminating in the Duck and Galloo Islands. 
Between this limiting line and the outlet of the lake at 
Kingston, not only is the depth shallower—not exceeding 
120 feet except in what may be two river channels, on either 
side of Duck Island, running inwards for ten miles towards 
Kingston—but its bottom is in nearly all directions rocky, 
and the contour of its shores—unlike the rest of the lake— 
is irregular, with deep bays and channels, which with the 
islands lie in a general north-east and south-west direction. 
The absence of the mud or clay which overspreads the lake 
elsewhere, and the two river channels opening towards the 
