1872.] 103 [Perry. 
been disturbed since its deposition, solid rocks have been reached, 
all written over with these strange hieroglyphics. In one instance 
a boulder, which had thus served as a plough-share, was found in the 
very furrow which it had formed.1 
Again it may be objected by some, that the surface of many rocks 
shows no signs of such work. If it be remembered that, in many 
eases, the best polished or striated surfaces, after an exposure of 
fifteen, twenty or thirty years, will have largely lost their striation,— 
that in rocks better able to withstand the action of the elements, a 
century must do a marked work of obliteration,—and that nearly all 
rocks, when first uncovered, have vestiges of such marking, — we 
shall, as we observe exposed surfaces without striz, find our objection 
fast fading into thin air. We may be led to believe that almost every 
weathered rock once bore marks of glacial action. Indeed, the ex- 
perienced observer can often detect such traces in the outline of the 
rock and in many other forms, when the unpractised eye will only 
see a blank, unlettered surface.2 It is thus doubtless true, that the 
vestiges of the ice-plane have been both largely effaced, and are in 
process of effacement, from most exposed surfaces; while almost 
every freshly bared ledge gives unmistakable evidence of former pol- 
ishing and striation. ‘So there are, at many low points, (take as an 
instance the Isle la Motte in Lake Champlain) several sets of strie 
crossing each other at varying angles. These are indicative of dif- 
ferent directions, and thus of successive stages of the glacier; they 
accordinely evince that the glacial times really consisted of several 
distinct, though closely related stages, instead of one uniform pro- 
cess of short duration, as some seem to have supposed. 
Now these facts—these evidences of action on the underlying 
rocks, in the way of denudation, polishing, and furrowing—which 
we encounter all over New England, and which never could have 
* been caused, some of them at all, and most of them even on a very 
limited scale, by icebergs, seem to be the legitimate work of ice 
slowly moving southward, in a vast sheet. ‘The various points cited 
1Emmons’ Geology of the Second District of New York. 
“Tt may be proper for me to quote the following statement by Professor Agassiz, 
which has recently fallen under my eye:—‘‘ These erased and obliterated surfaces 
(rocks moutounés) without scratch or furrow, are often intersected by large dykes, 
ihe surfaces of which show all the markings that have vanished from the adjoining 
rocks. The inequality in the level of the rocky hill and of the dyke shows the 
amount of decomposition since the glacial period.” For other kindred statements 
see his paper On the parallel Roads of Glen Roy. 
