206 OuIo STATE ACADEMY OF SCIENCE 
and in most instances probably consists of a mixture of materials 
from many places, some of it washed into the bay by streams, 
some derived from action of the waves on the shore. Materials 
from the same sources are found over much of the bottom of the 
bay but I do not recall finding muck or other remains of old 
marshes far from the present shores except in the submerged 
valleys. 
The thickness of the post-glacial deposits in any part of the 
bay can be determined approximately by subtracting the depth 
of the water given on the government chart of Sandusky 
Bay from the depth of the clay shown on Map III, allowing one 
or two feet for difference in water level at the times depths were 
determined. The water in winter is lower than in summer and 
so I have generally found its depth less than that shown on the 
government chart. 
In some places scarcely any mud covers the clay. In many 
places the uppermost part of the clay is so soft that the precise 
level at which it is struck cannot be told from its resistance to 
the auger pushed into it, but when pulled out it clings to the 
auger and an inspection of it as it is being removed with a stick 
rarely leaves any doubt as to whether it is clay or mud. The 
latter not only looks different, but has much less tenacity. In 
a great majority of cases the clay is blue, but in some places both 
near the south shore and the north shore it is red, not having 
been long enough in contact with organic matter to reduce the 
ferric to ferrous compounds. 
In some places, e. g., along the line extending north from the 
foot of Wayne Street to the Outer Range Rear Light, the transi- 
tion from mud to clay is abrupt. Here the mud is so soft that 
it is difficult to tell when the auger first touches it and the 
weight of one man is sufficient to push the auger nearly or quite 
to the clay. The hard and nearly level surface of the latter 
probably indicates that it was planed off by the waves a few 
centuries ago when the lake and bay had reached a high enough 
level. Shore currents probably carried the products of erosion 
away, leaving the bottom free from sediment. When the water 
had become so deep that the lower layers were no longer subject 
to agitation by the waves, light particles easily held in suspen- 
sion and so carried far from their source were deposited here, 
gradually forming a bed of soft mud resting upon the firm 
glacial clay. 
In going north along this same line, which is on the meridian 
of the court house, no sand was noticed until we were a mile from 
shore, where it was barely perceptible, gradually increasing 
toward the north. At a mile and a quarter it was necessary to 
