216 THE CANADIAN NATURALIST. [Vol. ix. 



and beauty. Emerging from the great oolite, the Avon wanders 

 at will over a wide plain or open valley of the Keuper marls and 

 alluvium until it reaches a spur of hard Carboniferous and De- 

 vonian rocks through which it has cut the romantic gorge of 

 Clifton more than two miles long and in some places 300 feet 

 deep between almost vertical walls. With its suspension bridge 

 of 800 feet span, no more exact counterpart of the Niagara rift 

 as seen from the Canadian namesake of the English " Clifton" 

 can well be found, except that in the latter case the work of 

 erosion is still in progress, while in the former it is complete and 

 the cataract has disappeared. 



But coming nearer home, our own rivers in Ohio supply many 

 similar instances. The Little Miami in its upper course flows 

 through a wide shallow valley of glacial drift of depth unknown. 

 But on reaching the village of Clifton (Greene Co.) it comes 

 upon a ledge of the hard Niagara limestone through which it 

 has long been and is still engaged in cutting a deep narrow chasm, 

 in some places about 60 feet in depth and less than 20 feet from 

 side to side with overhanging walls. Lower down the stream 

 where the gorge is older, it is more than 100 feet deep and 200 

 feet from bank to bank. After leaving the Niagara formation, 

 the river comes upon the soft shales and thin stone beds of the 

 blue limestone of the Cincinnati group, where the valley again 

 widens out until its sides are more than a mile apart with smooth 

 and gentle slopes. 



Numerous other examples might be quoted to show that this 

 "beaded" appearance of the channel of a river flowing for long 

 ages over rocks of various powers of resistance is not by any 

 means an uncommon phenomenon on the earth's surface. Not 

 only should it occur in theory but it does frequently occur in 

 reality. There is therefore no improbability in the supposition 

 that this pre-glacial Mohawk cut for itself such a channel. 



2nd. Dr. Newberry says : " The great and unequal depth of 

 the lake-basins renders it impossible that they can have been ex- 

 cavated by a continuous flowing stream." " Lake Huron is 800 

 feet in depth, while the buried channel which connects it with 

 Lake Erie is not more than 200 feet deep." " Lake Erie is 

 generally very shallow, and while its bed is no doubt traversed 

 by an old river channel which is very much deeper than most 

 parts of the lake itself, it is incomprehensible that it should not 

 have been cut as deeply by the old river as Lake Huron was, 

 since the rocks to be removed were the same." 



