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Great Lake Basins of the St. Lawrence. 283 
Lake St. Clair has an average depth of about 12 feet and 
a& maximum depth of 22 feet. The floor, except some 
limited areas of mud and clay in the centre, is overlaid 
everywhere with sand. The coast lines are low and often 
marshy, and, along the Canadian side fronting the counties 
of Essex and Kent, the land is barely elevated above the 
lake surface. The whole country here has quite the char- 
acteristics of the modern prairie, and its formation is un- 
undoubtedly due to similar causes which are still in opera- 
tion. Centuries of growth and decay of tall grasses, 
rushes and sedges in the extensive shallow marshes border- 
ing the lake gradually contributed a black loamy soil 
which even now is not much above the level of Lake St, 
Clair. And not only has there been a more intimate con- 
nection with Lake Hrie, but that the lake has at one time 
been somewhat deeper and is gradually filling up, is shown 
by the character of the deposits on its floor and by the ex- 
tensive, progressive delta of the St. Clair River. The 
heavier sediments in the waters coming from Lake Huron 
have been deposited in this lake, whilst the lighter silt 
appears to have been carried onwards towards and to Lake 
Hrie. 
The Detroit River, which now connects Lakes St. Clair 
and Hrie, flows through a flat prairie-like country, but 
slightly elevated in most of its course above the water 
level. At the outlet of the river, on the Michigan side, 
extensive marshes prevail for some distance along the lake 
coast. The soil, however, is a fine yellow or drab-coloured 
silt containing minute grains of sand—the filterings no 
doubt from the coarser material deposited in Lake St. 
Clair. 
For a lake of such wide area, Lake Erie is remarkably 
shallow, A line drawn from the City of Erie in Pennsylvania 
to Port Rowan, near Long Point, would have on its western 
side more than two-thirds of the lake area, and yet the 
maximum depth there does not exceed 84 feet. Again, a 
line from Pt. Pelée to Sandusky would form the eastern 
boundary of a large section, the greatest depth of which, 
