20 SANDUSKY FLORA. 



length of a mile its height was 20 to 25 feet or more, 

 and along the west side was clay covered with six 

 inches of black soil bearing shell bark hickory trees and 

 white oaks two and one-half feet in diameter. The last 

 of this large island disappeared in 1860. 



Gull Reef, north of Kelley's Island, has for many 

 years been the greater part of the time under water. 

 As late as 1850 it was an island on which stood a fish 

 shanty and a tree that probably took a hundred years 

 to grow. 



DERIVATION OF THE ISLAND FLORA. 



The facts stated in the preceding paragraphs 

 suggest the possibility of many of the plants now on 

 the islands having spread over them when a land 

 connection existed between them and the mainland. 

 Mr. Gilbert and others have concluded from a study of 

 the old lake beaches that when the melting of the ice to 

 the north opened an outlet for the glacial lake at 

 Niagara the waters went down till it occupied only one- 

 sixth the area that Lake Erie does now, and extended 

 no farther west than Erie, Pa. We have seen that the 

 submerged forests and stalagmites in the region about 

 Sandusky and the islands prove a lower condition of 

 the water when these were formed than has existed in 

 the present centurj*, and that the submerged river 

 channels in this region indicate that the depression of 

 the land as compared with the water has amounted to 

 not less than 32 feet. A lowering of the water 22 feet 

 would make it possible to walk from Kelley's island to 

 Catawba, and 30 feet from Put-in-Bay to Catawba, 

 excepting for a narrow channel, like a river which is 

 deeper than the rest. We would be entitled, therefore, 

 to conclude, even without a knowledge of observations 

 made in other regions, that the islands were connected 

 with the mainland in postglacial times. With this 

 conclusion it is much easier to harmonize the facts 



