234 OuIo 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. 
Number Approximate height |Highest aqueous |Height of aqueous 
of of valley southwest deposits deposits above 
Ridge. of ridge, feet. found | valley. 
| | 
1 ZO 
2 3. 4.55 {.59 
3 —2.5 5.4 (ag 
5 15 9.4 7.9 
6 4.5 12.138 7.63 
7 3.3 11.35 8.05 
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 71% 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 
