368 
GEOLOGY OF THE FOURTH DISTRICT 
Lower falls at Portage, from the west bank of the river. From a sketch by Mrs. Hall. 
CHAPTER XYIIL 
Modern action of rivers—Freezing of water in river channels. 
The numerous examples which we have in the Fourth District, of rivers flowing in deep 
narrow gorges, naturally prompts the inquiry whether the present streams can have formed 
the channels in which they now flow ? Fully to answer this question, would lead to the con¬ 
sideration of numerous circumstances, and open a wide field of inquiry. Every river and 
smaller stream, even the most insignificant, will furnish facts for illustrating the subject. 
Although we may find these modern operations upon a much smaller scale than in the moun¬ 
tainous regions of Northern New-York, still the effects are everywhere visible. The trees 
standing upon the very margin of a stream falling over a rocky stratum, or upon the edge of 
a cliff with their roots projecting more than half over the precipice, or even the tree itself 
prostrated and held suspended only by a few fibres which penetrate the soil beyond the chasm, 
are eloquent monuments of the changes wrought by time upon the rocky cliffs and deep river 
gorges. These show that nature in all her operations is constant and unremitting, and that the 
