in Pennsylvania, it is certain that the ice was deep enough
to surmount the ridge of the Alleghanies where they are
two thousand and more feet in height. At the least cal-
culation the ice must have been five hundred feet thick,
in order to secure the movement of which there is evi-
dence across the Appalachian range. Supposing this to
be the height of the ice above the sea on the crest of the
Alleghanies, and that the slope of the surface of the ice-
sheet was as moderate as Professor Smock has estimated
it (namely seventeen feet to the mile), the ice would be
upwards of six thousand feet in thickness in the latitude
of the Adirondacks, which corresponds closely with the
positive evidence we have from the mountains in New
England.
