Page:Popular Science Monthly Volume 49.djvu/25

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13
NIAGARA AS A TIMEPIECE.

broom had swept the accumulated dirt of ages from the northern country and filled up the great valleys, the lake region was covered with water; whether arms of the sea, as is probable, or as lakes, of which the barriers are not indicated, is immaterial in the history of the river, for under either condition the old shores were produced, and these we have surveyed. From them we learn the story that all the lakes formed one broad sheet named the Warren water. From time to time its surface was lowered, and at each pause new stands were formed, only to be abandoned by further sinking of the water. At last the aboriginal Warren water subsided so that it became divided in two smaller sheets—the Algonquin gulf, occupying more or less of the basins of Lakes Huron, Michigan, and Superior, and the Lundy gulf, extending over much of the Erie and the Ontario basins. With the continued lowering of the gulf, or, more correctly, the rising of the land, for no evidence of lake barriers has been found, the Lundy gulf became dismembered, forming Lake Erie, then much smaller than now, and the Iroquois gulf occupying the Ontario basin, the deserted shores of which have now an elevation much above the

PSM V49 D025 View of the american falls.jpg

Fig. 13.—View of the American Falls.

present altitude of the lake. Then Niagara Falls had their birth, and the river descended only a little more than half as great a height as to-day into the gulf (Fig. 10) which came to the mouth of the gorge. The lowering continued until the descent of the river was much greater than at present, and the shores of the lake receded not merely eight miles to the present margin of the