1872.] 109 [Perry. 
at, they are accidents rather than uniform accompaniments, of a con- 
tinental ice-sheet. 
Primarily deserving of notice is the accumulation of travelled mat- 
ter. A prominent form, in which this detrital material occurs, is _ 
strictly an accumulation; since it is found in heaps, or piled up m 
peculiar masses. Angular boulders are also occasionally met with 
in long lines, as if they had been accumulated with design. Both 
these aspects, under which travelled material may be seen in differ- 
ent parts of the country, are calculated at once to arrest the atten- 
tion of the geolocist, and to attract the eye of the ordinary observer. 
Reference is now made to moraines and trains of boulders. As the 
mass of ice slowly melted, the matter which had been pushed on by 
it, and to some extent before it, must have been left, in more or less 
nearly east and west ridges, along its southern border. These, how- 
ever, have been greatly modified by the constant action of agencies 
at work in the closing Glacial period, and during subsequent times. 
But in addition to these deposits, there are still to be met with in 
vast force and in unmodified condition, the detrital materials which 
lay beneath the ice-sheet, and were left in place on its retreat. 
These in one view may be regarded as morainic, though they be 
moraines in a discuised form.t Accordingly the deposits thus left as 
the remnants of the Middle Glacial period, are only now and then 
recognized as terminal moraines. 
The morainic accumulations which found place, as the local gla- 
ciers slowly wasted, near the close of the Drift period, are in much 
sreater degree characteristic, since they have a more marked outline, 
and because they are frequently seen lying at right angles with the 
direction of the ice-movement during what were in New England 
the Middle Glacial times. While the earlier deposits, for the most 
part, cover the whole region, and especially are seen to occur on the 
more elevated grounds, or in the broad level depressions, from which 
the great ice-sheet would first disappear, the later are usuaily found 
in valleys which were probably occupied at a more recent day by 
local ice-streams. But not merely terminal moraines occur; those 
known as lateral are also met with. They were doubtless formed 
during these later times, indeed they must have found place, though 
1] have here, and in another paper, unwittingly called ‘‘ disguised moraines,’’ 
what I now suppose Professor Agassiz has described as ‘‘ ground moraines.” Of 
this I was not aware, until I read his recent paper, ‘‘ On the evidence of the Evxist- 
ence of Glaciers in the White Mountains.” 
