194 Cincinnati Society of Natural History. 
Oth. “ Lacustrine deposits,’ occupying the basin of the lakes, and 
for Lake Erie, divided into the “ blue marly sand,” and the coarse sand 
and gravel. The.“blue marly sand,’ commonly called the blue clay of 
Lake Erie, is seen skirting the shore almost everywhere, if the coast is 
not rocky,—its upper face nearly horizontal, and rising from forty-five 
to sixty feet above the water. It is of a light blue color, so fine as 
scarcely to show between the fingers any grit, homogeneous, and in a 
dry state compact, but brittle. Very rarely, may be seen a primitive 
pebble, thin layers of leaves and lignite. It is distinctly and horizon- 
tally laminated, and at Cleveland is composed of about 75 per cent. im- 
palpable sand, 3 per cent. iron, 6 to 7 per cent. carbonate of lime, 9 per 
cent. carbonate of magnesia, and of vegetable matter and sulphur. It 
is impervious to water, and thus causes thousands of springs to ap- 
pear at its surface, which, passing out over the edges, dissolve and 
carry it away very fast, forming a quick sand. Its edge is presented 
to the action of the waves, which dissolve and carry it away rapidly. 
As it is not tenacious like clay, and not capable of sustaining itself 
under its own weight, and that of the sand stratum that rests upon it, 
there are continual breaks and slides along the banks, on both the 
American and Canadian shores. These avatanches of earth are from 
one to four rods in width, breaking off in irregular patches, and some- 
times sinking, in a night or in a few hours, twenty or thirty feet, leav- 
ing huge fissures through which the water of the springs passes, and 
rapidly washes the earth into the lake. 
At the water’s edge, the slide frequently raises a bank of about the 
width of the break, several feet above the surface, driving back for a 
short time the line of the shore. But the waves acting incessantly 
dissolve the new barrier, and soon commence their attacks upon the 
body of the fallen mass, which disappears, and is before long followed 
by a fresh avalanche from above. 
At the city of Cleveland, where the bluff shore rises 70 feet above 
the lake, the encroachment since the survey of the town in 1796, has 
been at the foot of Ontario street, 265 feet. ‘The Canadian shore, from 
Detroit river to Long point, is losing faster than the American. Be- 
tween Port Stanley and Port Burwell, on the British side, the superior 
face of the blue marl is about sixty feet, or fifteen feet higher than at 
Cleveland, and has in the upper part a lighter or more yellow color. In 
composition the yellowish portion is more argillaceous than the bright 
blue, and appears to correspond with the yellow clay stratum of Lake 
Champlain. The greatest thickness ofthe blue marls can not be com- 
