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Ohio State Academy of Science 



selves might also ascend from the bay toward the lake. So the 

 ridges were dug into in about 150 places altogether with a view 

 to finding the highest trace of water action in each. The 

 accompanying table gives the result, the data being reduced to 

 mean lake level. 



Heights of Principal Ridges and of Valleys Southwest 



OF Them. 



Deepening of Lake Erie. 



As each of the principal ridges was formed by a great north- 

 east storm occurring at a time of high water the progression in 

 level from the older to the higher is due to an elevation of the 

 level of Lake Erie compared with the land. The approximate 

 rate of change is determined by dividing the difference between 

 the heights of the aqueous deposits in any two of them by the 

 number of centuries intervening between their formation. Each 

 ridge higher than all those to the southwest of it was probably 

 formed by one of the greatest if not the greatest storm, of the 

 century or one that was more potent than others because of the 

 high water at the time of its occurrence. That they were 

 formed under similar conditions is evidenced by the fact that in 

 each the highest indication of water action is about 73^ or 8 feet 

 higher than the valley behind it. The accompanying table 

 shows the rate of subsidence based on a comparison of the older 

 ridges with Ridge 6, the highest. Ridge 3 gives a rate consid- 

 erably higher than the others. It may be that it was not formed 

 at the time of the highest water that occurred for many years, 

 though at a time of high water. If we compare it with Ridge 7 



