210 Ohio State Academy og Science 



under the bay until the water broke through the roof of the mine. 

 Gypsum has also been found near shore between Fletcherville- 

 and Plaster Beds, and in 1902 a good bed was found 13-'2 miles 

 south of the bay on Mr. Meggit's farm in Margaretta Township. 

 In view of its occurrence both north and south of the bay and 

 near the bay near the north shore it seems probable that it 

 once extended over considerable of the region now occupied by 

 the portion of the bay west of the bay bridge. The relatively 

 rapid solution and erosion of the gypsum compared with the 

 more resisting limestone may have produced this broad valley. 

 Much of the earlier plaster was derived from boulders, so it is 

 likely that the glacier assisted in enlarging this valley. East of 

 Sandusky the depth of limestone below the surface is shown on 

 Map VI. An inspection of this chart will show that over most of 

 the region the rock is not far from level. It rises near the 

 Sandusky shore and near Biemiller's cove. It drops off rapidly 

 to the north just as it does along the city front, also to the east 

 of a line extending from the Jarecki Chemical Works to the Lake 

 Laboratory. 



In other parts of the bay I have never struck rock except in 

 a few places near shore, e. g., near the mouth of Mill Creek and 

 near the south end of Johnson's Island. 



CEDAR POINT. 



Cedar Point is the peninsula, 7'ji miles long, forming part 

 of the eastern boundary of Sandusky Bay. It is not, as has 

 been supposed, a mere sand spit, but has a foundation of clay 

 resting upon the rock and extending, in the middle section, nearly 

 up to low water level. It may be divided into three portions 

 which we will call the bar, :the middle or dune section, and the 

 terminal or ridge section. 



The Bar.* 



This is a low narrow strip of sand extending from Rve 

 Beach, 23^4 miles west of the Huron River, to the Carrving 

 Ground, a distance of about -i^i miles. The height of the crest 

 above .mean lake level averages about 6} 2 feet, in the highest 

 places barely exceeding ten and in the lowest descending to a 

 little less than five. From the crest toward the lake a bare 

 beach slopes steeply for a foot or two then gradually to the water 

 whose height of course determines its breadth. At low stages of 

 the water, such as prevail in fall and winter, the breadth is about 

 four rods, continuing for miles with little variation. It does not 



