The ice age in North America and its bearing upon the antiquity of man5th edwith many new maps and illus., enland rewritten to incorporate the facts that bring it up to date, with chapters on Lake Agassiz and the Probable cause of glaciation . aled to by ProfessorNewberry in support of the theory that the ice was a promi-nent agent in the formation (»f the basins of the GreatLakes. As this is so important a region for glacial study, I willgive somewhat in detail the i-esult of my own recent obser-vations. There are twelve or fifteen islands near the west-ern end of Lake Erie, of which Kellys,
The ice age in North America and its bearing upon the antiquity of man5th edwith many new maps and illus., enland rewritten to incorporate the facts that bring it up to date, with chapters on Lake Agassiz and the Probable cause of glaciation . aled to by ProfessorNewberry in support of the theory that the ice was a promi-nent agent in the formation (»f the basins of the GreatLakes. As this is so important a region for glacial study, I willgive somewhat in detail the i-esult of my own recent obser-vations. There are twelve or fifteen islands near the west-ern end of Lake Erie, of which Kellys, North Bass, MiddleBass, South Bass, and Pelee are the principal, each having GLACIAL EROSION AND TRANSPORTATION. 263 an area of several square miles, and none of tlieui rising 100feet above the surface of the lake. They all consist of thehard limestones of the Niagara series. In every instance, asone approaches them from the eastern side, his attention isattracted by the remarkable depth and continuity of theghicial grooves running nearly east and west upon them, andwhich rise out of the water, and continue to the summit ofthe islands, or until they are covered by the ground moi-aincwhich has nut been washed away by the waves. In some. Fi(i. 78.—Glacial grooves ou east side of South Bass Island. Lake Erie, luimiiii; west 10 south. instances, these grooves are tw<^ or three feet deej), and ex-tend many rods in plain sight. Nor are they in all casesstraight, but sometimes are extremely tortuous, winding alongin their course like the channel of a sluggish stream. It isevident, in some cases, that the main features of these deep-est grooves have been determined by preglacial or subglacialwater-action, and that the ice, or the ground m<^traine under
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