^ 



# 



in Massachusetts. 81 



form but a faint idea of tlie force exerted by a stream in 

 such circumstances. The ice^ towards the source of the 

 river^ is generally first brbken in pieces by the swollen 

 waters. Large masses are thus thrown up edgewise^ and 

 forced underneath the unbroken sheet, and the whole bed 

 of the stream is blocked up ; perhaps too where the banks 

 are high and rocky. The water accumulates behind the 

 obstruction until the resistance is overcome ; and the 

 huge mass of ice and water urges on Its way, crushing 

 and jamming together the ice which it meets, and thus 

 gains new strength at every step. Often, for miles, the 

 stream, prodigiously swollen, is literally crammed with ice, 

 so that the water disappears ; and a slowly moving column 

 of ice Is all that Is seen- This presses with such force 

 against the bottom and sides of the stream, as like heavy 

 thunder, to cause the earth to tremble for miles around. 

 Sometimes the body of ice becomes so large, and the fric- 

 tion so great, that the waters are unable to keep it in 

 motion, and it stops; while the river is turned out of Its 

 channel, and is compelled to flow for weeks, and even 

 months, in a new bed. 



It is impossible that such floods should not operate 

 powerfully to modify the surface in alluvial regions, and 

 to excavate the beds of rivers. I am confident that no 

 other agent in the mountainous parts of this state is so 



r 



energetic. Though its efiects are not small in alluvial 

 regions, yet I apprehend that its maximum power is seen 

 in those rocky ravines, through which such rivers as the 

 Deerfield and the Westfield pass, among the mountains. 

 Masses of rocks of various sizes, some ten, fifteen, or 

 twenty feet in diameter, may here be seen, some of them 

 torn up from their beds and removed a considerable dis- 

 tance^ strewing the bottom of the streams, and at low 



