270 ANNUAL OF SCIENTIFIC DISCOVERY. 



analogue in the continent of Europe ; and it constitutes in America, 

 the most marked feature in the geology of the quarternary period. 

 Coming from the sea coast, we meet with it first, on the shores of 

 Lake Erie, where it forms slopes, and terraces, composed at the lower 

 parts of blue clay, and hard pan, surmounted by loam and gravel. A 

 moment's observation convinces any one, that these ridges, terraces 

 and slopes, are not the result of violent action ; but that they were 

 deposited in quiet waters. As the fossils are rare, as they differ in 

 many respects from the Laurentian, doubts naturally arise as to their 

 origin, and their age. Are they hiarine, or are they lacustrine ? The 

 same doubts rest upon the loamy deposites, that form the surface 

 material over the vast space, occupied by the States of Wisconsin, 

 Illinois, and Iowa, and the shores of the Mississippi Some geologists 

 have called them by the name of loess, from their resemblance to the 

 " loess " of the Rhine. 



But these doubts have recently been removed, by the discovery by 

 Mr. Whittlesey, in the blue marly clay of Lake Erie, at Cleveland, of 

 fresh water and terrestrial shells, (Heleciance and Planorbis,) at 25 to 

 50 feet above the level of the water. The same gentleman has col- 

 lected numerous specimens of buried timber and leaves, from the same 

 deposites, in which they are very abundant. M. Lesquereux has 

 recognised among them, the leaves of the spruce (Abies nigra^) the 

 common cranberry (Vaccmium) which now grows in that country, 

 and many species of Cyperaceece. 



Mr. Whittlesey soon after discovered fresh water shells in the loess- 

 like deposites, on the shores of the Mississippi, including many species 

 of Planorbis, one of Cyclas, and a Physa, at 60 to 180 feet above the 

 level of the river. The same shells have been recently observed near 

 St. Louis, (250 to 300 feet above the stream,) and at New Harmony 

 upon the Wabash. Very lately, Dr. Rigsby has found on the banks 

 of the river Notawassaga, that empties into the Bay of St. George of 

 Lake Huron, in Canada, a bed of fresh water shells, (Unios) covered 

 with deposites of much thickness, but he has not given us their eleva- 

 tion above the lake. Mr. Murray, of the Canadian Geological Society, 

 has explored the northern shore of Lake Erie, and finds that the 

 superficial deposites are composed of the same materials as those upon 

 the southern shore opposite ; and although he has not discovered there 

 any shells, he does not doubt but the marly clays of Canada, and the 

 sandy and loamy beds resting upon them, were deposited by the same 

 waters, as those on the American side. If we examine the map, and 

 the position of these deposites, and remember the elevation at which 

 the fossils are found, at different points, we must infer, that there 

 existed at the quartenary epoch, two immense sheets of fresh water in 

 North America ; one occupied the basin of the Upper Mississippi, the 

 other, that of the Canadian Lakes, but both formed one vast sea of 

 fresh water ; from which, however, we must exclude the basin of Lake 

 Ontario, which was marine, or salt water. The comparison of the 

 levels, where the shells were found, at Cleveland, and on the Mis- 

 sissippi, shows that these great basins were not then isolated, but com- 



