262 THE GLACIAL LAKE AGASSIZ. 



the vicinity of Quebec. Theuce its currents pushed up the valley by Alon- 

 treal, and also down the valley, filling the broad estuary of the river to the 

 gulf; and on that tract, at or below Quebec, doubtless the last remnant of 

 the ice barrier was melted away, allowing the sea ingress westward to Lake 

 Champlain, to the mouth of Lake Ontario, and to Allumette Island, in the 

 Ottawa. Previous to this, while an arm of the sea had been washing 

 the ice border and thus increasing its speed of retreat in the Gulf of St-. 

 Lawrence and Avest toward Quebec, the glacial lake's waves on the other 

 side of the narrowing ice belt in this valley had likewise hastened its 

 departure. Gradually this lake, which I have named Lake St. Lawrence,! 

 had extended beyond the basin of Lake Ontario to fill at length the lower 

 part of the Ottawa basin, probably to the mouth of the ]\Iattawa, and it had 

 spread eastward around the northern side of the Adirondacks to Lake 

 Champlain and Montreal, and down the St. Lawrence Valley probably to 

 Quebec or fartlier, when the ice dam between it and the sea disappeared. 

 The glacial Lake St. Lawrence, imtil this time outflowing to the ocean by 

 the Hudson River, then ceased to exist; Lake Ontario became a separate 

 sheet of fresh water; and the sea, at a somewhat lower level than Lake St. 

 Lawrence had held, stretched to the Thousand Islands, where the St. Law- 

 rence River, at first only a few miles long and with scarcely perceptible 

 fall, discharged the outflow of Lake Ontario into the prolonged Gulf of 

 St. LawTence. 



Another branch of this theme needs to be added, telling the history of 

 the continuous Hudson and Lake Champlain Valley during the recession 

 of the ice-sheet, up to the time of this opening of its northern ]X)rtion to the 

 ocean. The absence of marine fossils in beds overlying the glacial drift 

 on the shores of southern New England, Long Island, and New Jersey, 

 and the watercourses which extend from the terminal moraine on Long 

 Island southward across the adjacent modified drift plain and continue 

 beneath the sea-level of the Great South Bay and other bays between the 

 shore and its bordering long beaches, prove that this coast stood higher 

 than now wdien the ice-sheet here extended to its farthest limit. A 

 measure of this elevation of the seaboard in the vicinity of New York 



1 Am. Jour. Sci. (3), Vol. XLIX, pp. 1-18, with map, .Ian., 1895. 



