120 GLACIAL PHENOMENA IN MAINE. 
these marks from spot to spot over surfaces 
where they were once continuous. When I 
say that I followed the glacial marks, compass 
in hand, from north to south, over a line a 
hundred miles in length, I do not mean that 
I never lost sight of them for that distance; 
hut simply that one set of lines, which always 
ran due north and south, unless deflected as 
we shall see by some local cause usually ex¬ 
plicable on the spot, might be traced at inter¬ 
vals over all the rocky surfaces. If they dis¬ 
appeared under a stream on its northern shore, 
they reappeared on the southern side; if hid¬ 
den for a time by some mass of vegetation, 
they were found again farther on ; and thus — 
allowing for natural and inevitable interrup¬ 
tions — it may be correctly said that they are 
continuous over the whole country. The gla¬ 
ciated surfaces — to express in one word the 
combined action of glaciers on the rocks over 
which they move — present the most varied 
outlines, sometimes flat, sometimes bulging, 
with inclined slopes. But whether more or 
less prominent, they are always rounded, dome¬ 
shaped, and the larger furrows, like the smaller 
stride and grooves, are invariably straight. 
