Goodrich : A Trip to Islands in Lake Erie. 529 



here, though it would have been fair for mainhmd collecting, seemed 

 insignificant after Middle Sister. 



East Sister, close by, was a large island and had been cultivated in 

 previous years. The picking was small, the gaps between snails long, 

 and the Ephemeridce a plague. We "did" one end of the island, the 

 only promising part, and rowed back to the powerboat. We had 

 planned to make Hen Island before dark and, if possible, one or both 

 of the islets known as the Chickens. Halfway to Hen Island, a storm 

 forced the revision of plans, a sudden change of course, and flight to 

 shelter at Put-in-Bay. This proved to be one of the worst gales of 

 the season and reluctantly on the fourth we gave up hope of visiting 

 other islands, the aspect of which from the lake indicated habitation 

 by snails. Some collecting was done at Put-in-Bay, but without 

 turning up anything not represented in Mr. John A. Allen's list, 

 recently published in the Nautilus. The shells here corresponded to 

 those of the mainland and might tend to show that, as an island, 

 Put-in-Bay is of more recent formation than the other islands. 



The rocks of the islands we visited belong to the Silurian series 

 known as Monroe. Where the exposure is on the water, the rocks are 

 very much weathered. In some places they are cut and carved into 

 picturesque caves. With geologists the islands are most distinguished 

 for their glacial records. Upon nearly all of them are beautiful 

 grooves and striae, sculptured by the ice. One series of grooves on 

 North Harbor Island was utilized extensively by the nesting terns. 



The basin of Lake Erie was originally a shallow valley with free 

 drainage. In the successive stages in which the ice M^all retreated 

 and lakes formed at its foot (Lakes IMaumee, Whittlesey, W'ayne, 

 and Warren) what are now the Erie islands were covered with ice 

 and water. In the Lake Algonquin stage, in which the upper lakes 

 discharged through three outlets instead of one as at present (if the 

 the artificial Chicago drainage canal be excepted) the lowlands between 

 Lakes Huron and Erie were uncovered, Lake Erie fell to a level below 

 that of to-day, and the islands appeared above the waters. For a 

 time a few of them may have been parts of the principal land-mass. 

 Probably the peopling of the islands with animal and vegetable life 

 began at this period. Later, and after the final passing of the glacial 

 ice, the Great Lakes passed into the Nipissing stage, the Chicago 

 outlet was closed and an increased volume of water poured through 

 Lake St. Clair and the Detroit river. Still higher water came when 



