458 On the Formation of Valleys. 



falls arc not precipitated from aii open height of higher 

 ground, but down into a deep chasm, or rocky valley, 

 formed, undeniably, by the violent action of the water, 

 which has continued, and is still continuing, from the de- 

 tritus of the rock, to remove the fall higher up the stream : 

 such strictly is the case with the far-famed Palls of Niagara. 

 The surrounding country is nearly on the same level, and 

 the river is propelled over an immense bed of rock, down 

 into a profound valJcy, which extends for nine miles below 

 the falls, and with every appearance of having been formed 

 by the progressive removal of the fall backwards, in conse- 

 quence of the gradual waste of the rockby the destructive 

 action of the water. 



But there is another point of view in which this magnifi- 

 cent waterfall ought to be considered as eminently illustra* 

 live of the subject under consideration. The height of the 

 fall, and what are called the rapids immediately above it, is 

 upwards of two hundred feet ; and there is a still further 

 considerable fall -in the descent of the river from the lake 

 above. • - ■ * 



• Now it certainly requires but a small effort of mind to 

 perceive that the vast stratum of imperishable rock which 

 crosses the channel of the river^ has alone prevented the 

 St. Lawrence from excavating one of the largest and most 

 capacious valleys on our -globe, and that the excavation 

 would have extended upwards into lake Ontario, liberating 

 its waters,- and leaving the river to form, for itself, a chan*- 

 jief through the central antl.deepest parts of the exhausted 

 hke. 



•. The retreat of these waters would be productive of another 

 vast fall in the channel from lake Erie, and that fall again 

 excavating a valley upwards, and into the lake, would oc- 

 casion the exit of its waters, which again, would produce a 

 fall and excavation up into lake Huron, the retreat of whose 

 waters would be followed .by falls from, and excavations 

 irito, lakes Superior and Michigan; and hence this exten- 

 sive chain of immense lakes would disappear, leaving iu its 

 im equally extensive chain of valleys and alluvial flats, 

 similar, -but on a far more gigantic scale, to the thousands 



of 



