282 GLACIERS IN THE WHITE MOUNTAINS. 
the unconsolidated snow at the upper part of the mass, move 
down at the rate of from three hundred to five hundred feet 
in a year. The moving of a mass of ice, it may be a dozen 
miles in length, a mile wide, and a thousand feet deep, is 
attended by a tremendous grinding upon the rocks over — 
which the glacier passes. By extended examinations geolo- 
gists have become convinced that in old times these great 
bodies of ice covered immense tracts where now no ice is 
seen, and nothing but the polishing and scratching upon the 
ledges remains. This furrowing and polishing resembles s0 
exactly the results now being produced beneath the present 
glaciers of the Alps, as to be regarded as positive evidence 
of the movement in a former age of vast bodies of ice ovel 
the rocks so scored. ; 
There is at first sight a marked difference between the 
glacial furrows and polishing in the Old World and in the 
New. In Europe these marks upon the rocks are found wd 
certain mountain regions, and always referring Us by nr 
direction to the higher parts of the mountain groups; thus 
showing that the glaciers moved down from the higher . 
the lower lands. This is plainly seen in the Alps, in Sar 
dinavia, and Great Britain. In America, the traces upon 
the rocks, as a general thing, appear to have been produ 
by a far more wide-spread operation, inasmuch as the y 
rows have a prevailing southerly direction, regardless 
topographical features to a remarkable extent, as they pas 
directly over and across some of the largest ranges of gee 
tains. Throughout New England, the most common ppt 
of the furrows is about s.s.ẹ. The wide extent wire 
traces would seem to point to some very general ope sdb 
as a cause. What this operation was, Or rather i A 
> 
how it worked, is by no means yet understood by g°° 
t isto 
nor does it concern us here, as the object at prer atò 
call attention to a different class of glacial gpa S 
appear to show, contrary to the opinion for & long ee 
held, that besides this general operation, which ma, 


