Lacustrine Deposits in the vicinity of the Great Lakes. 93 
The immediate effect of these storms, as above stated, is to 
carry away the base of the steep bank along the shore, moving 
the sand and pebbles by successive steps towards the south. But 
the finer materials—the soft clays—are suspended in the water of 
the lake, causing it to be muddy for a great distance from the 
land. The quantity of matter suspended in the water, and the 
distance it is carried out, will of course vary according to the 
force and direction of the storm, the configuration of the coast, 
the material of the bank acted upon, &c. When the storm abates, 
the agitation of the water ceases, and the suspended matter is thrown 
down in the form of a thin deposit of mud, on the bottom of 
the lake. If it falls in water so deep as to be beyond the influ- 
ence of the surface waves, it must remain as a permanent deposit. 
Another storm produces another layer, and should it come froma 
different direction, there may be a slight difference in the nature 
of the material deposited. By this process, continued through a 
succession of years, a large amount of fine sediment will be ac- 
cumulated in the bottom of the lake. The analogy between de- 
extremity of Lake Erie. In passing over the railroad westward 
om Detroit, no boulders, or other indications of drift, are found 
on the surface until we pass the ancient lake beach at Ypsilanti, 
beyond which they begin to appear in great numbers. t of 
that beach was evidently once the bottom of a lake. 
Some of the most interesting deposits of this'kind are found 
Within the limits of the city of Milwaukee; and it is from them 
that the material is taken for the manufacture of the much cele- 
brated cream-colored brick, of this city. Such is the richness 
