206 Ohio 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 nearl}^ 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 necessar}^ to 



