1872. { 63 [Perry. 
nection with the agency of ice, under some form of its working, it is 
difficult to conceive. 
(2.) The location of perched rocks. These masses being likewise 
travelled material, and for the most part angular, are generally known 
as boulders or erratics. Strictly speaking, boulders are such as are 
rounded, while “ erratic” properly applies to an angular block which 
is usually far travelled, reference being had to the fact that it was 
once a rover or wanderer, it having strayed from its parent ledge. 
While boulders and erratics occur in places all over the northern part 
of the continent, these travelled rocks are specially met with on the 
summits of high hills and of mountain peaks, and in some cases in 
extraordinary abundance. Because of the peculiar position in which 
they are often found they have come to be called “ perched,” per- 
haps for the reason that they may occasionally almost remind one of 
so many birds gone to roost. In given cases they are situated in such a 
way as to appear to have been thus placed only by the exercise of con- 
sideration and intelligent care,—as it were with plan and forethought. 
Some of them weighing many tons are almost exactly poised on the 
underlying rock, or upon a small boulder, so evenly balanced, in 
many instances, that they may be tilted with ease. Why these erra- 
tics should thus occur —not so much why they are poised, as why 
they should be found — perched in many cases in unusual numbers 
on the crests of solitary hills, at first sight seems very strange. It is 
thought, however, that by invoking the agency of ice, we discover a 
ready solution of the whole matter. 
(3.) The position of ancient beaches. The remains of what have 
been called old sea-beaches occur at various points, and at considera- 
ble heights along the flanks of our New England mountains. Rolled 
material is met with at these places which, so far as can be judged, 
is just like that of our existing shores. Itis in the form of sand, of 
rounded pebbles, and of stones evidently smoothed in substantially 
the same way as similar materials now found on the banks of streams 
and lakes, and along the sea-coast. ‘That some of these are remnants 
of ancient beaches, that they are the surviving portions of old shore 
lines, is no longer doubted by the many competent observers who 
have examined them with care. The striking peculiarity of these 
old beaches is the great height at which, in several instances, they 
occur. Some of them are at elevations between two thousand and 
twenty-five or twenty-eight hundred feet above the ocean. Such is 
the case with those met with in Ripton, Vermont, and in Peru, Mas- 
