1872.] Le [Perry. 
up of its channel with ice; who has noticed the changes wrought by 
its occasional breaking away of the ice and its subsequent obstruc- 
tion by new barriers; who has patiently inspected the phenomena 
presented in the slow removal of the ice by thawing; who has 
thoughtfully noticed the successive recessions and advances made in 
these ways by the water for weeks; and who has afterward studied 
the deposits laid down in miniature, under such circumstances, over 
the flats; whoever has taken this course, has witnessed within a 
small compass some of the conditions and modes of action which 
were probably prevalent at a former time on a macnificent scale, and 
has seen the consequent irregularity of deposition, as if in connec- 
tion with the ebb and flow of the tide, which is so characteristic of 
some of the stratified glacial deposits. Will one make a study of 
such freshets, from year to year, as they occur in many New Eng- 
land valleys; indeed, on not a few of the streams all around the 
globe, in the colder portions of the temperate zones; will he do this 
remembering that, during the waning power of the Ice-period, there 
were probably annual flows of far greater volume, tending thus from 
time to time to elevate and depress the barriers, and prevent a uni- 
form level of the waters; will he also bring to mind such analogous 
conditions and agencies as naturally suggest themselves to a thought- 
ful observer, he need have little further trouble with the deposits in 
question. 
If this view be substantially correct,—and whether it be or not, 
any one may satisfy himself, who will closely observe such action in 
a limited way, during a New England spring,—it certainly leads us 
to question much that has been advanced by Professor Dana in re- 
spect to those deposits, which he supposes were laid down in part by 
the ocean alone, in part simply by the waning ice-mass, and in part 
by the two operating in connection. As a consequence of his sup- 
posed subsidence of the land, he says, “ unstratified and stratified 
drift” (the latter including the so-called modified drift, as well as a 
large part of the “alluvium” of river valleys) “ were formed simulta- 
neously, and both in the Champlain era.” The connection, in which 
these words occur, clearly shows that, in the view of the author, the 
ice-sheet was already largely beneath the ocean, and that the results 
named were effected under such a state of things. As before inti- 
mated, there is no proof of any considerable submergence at the 
; 1 Paper cited, p. 67. 
