LAKES IN NORTH AMERICA.

183

J 60 feet in depth. It is estimated that 6 70,000tons of water are dashed every minute withinconceivable force against the bottom, andare undermining and wearing down the ad-jacent rocks. Since the banks of the cataractwere inhabited by Europeans, they have ol)-served that it is progressively shortening thedistance from lake Erie to lake Ontario .When it has worn down the intervening cal-careous rocks and effected a junction, theupper lake will become dry land, and form anextensive plain, surrounded by rising ground,and watered by a river or smaller lake, whichwill occupy the lowest part. In this plainfuture geologists may trace successive strataof fresh-water formation, covering the sub-jacent crystalline lime-stone. The gradualdeposition of minute earthy particles, or themore rapid subsidence of mud from suddeninundations, will form different distinct beds,in which will be found remains of fresh-waterfish, of vegetables, and of quadrupeds. Largeanimals are frequently borne along by therapidity of the current, and precipitated downthe cataracts; their broken bones mixt with

calcareous