PROGRESSION OF GLACIERS. 
235 
idea of their structure and mode of action, as 
well as to know something of the important part 
they have played in the later geological history 
of our earth. It would, indeed, be out of place, 
were I to undertake here a discussion of the dif- 
ferent views entertained by the various students 
who have investigated the glacier itself, among 
whom Dr. Tyndall is especially distinguished, or 
those of the more theoretical writers, among 
whom Mr. Hopkins occupies a prominent position. 
Removed, as I am, from all possibility of re- 
newing my own observations, begun in 1836 and 
ended in 1845, I will take this opportunity to 
call the attention of those particularly interested 
in the matter to one essential point with reference 
to which all other observers differ from me. I 
mean the stratification of the glacier, which I do 
not believe to be rightly understood, even at this 
moment. It may seem presumptuous to dissent 
absolutely from the statements of one who has 
seen so much and so well as Dr. Tyndall, on a 
question for the solution of which, from the 
physicist’s point of view, his special studies have 
been a far better preparation than mine; and 
yet I feel confident that I was correct in describ- 
ing the stratification of the glacier as a funda- 
mental feature of its structure, and the so-called 
dirt-bands as the margins of the snow-strata 
successively deposited, and in no way originating 
