ed through what is now called the Wind-gap, a
place several miles to the westward, and above an hundred feet higher
than the present bed of the river. This Wind-gap is about a mile broad,
and the stones in it such as seem to have been washed for ages by water
running over them. Should this have been the case, there must have been
a lake behind that mountain; and, by some uncommon swell in the waters,
or by some convulsion of nature, the river must have opened its way
through a different part of the mountain, and meeting there with less
obstruction, carried away with it the opposing mounds of earth, and
deluged the country below with the immense collection of waters to
which this new passage gave vent. There are still remaining, and daily
discovered, innumerable instances of such a deluge on both sides of the
river, after it passed the hills above the falls of Trenton, and reached
the champaign. On the New Jersey side, which is flatter than the
Pennsylvania side, all the country below Croswick hills seems to have
been overflowed to the distance of from ten to fifteen miles back from
the river, and to have acquired a new soil, by the earth and clay
brought down and mixed with the native sand. The spot on which
Philadelphia stands evidently appears to be made ground. The different
strata through which they pass in digging for water, the acorns, leaves,
and sometimes branches which are found above twenty feet below the
surface, all seem to demonstrate this."

How little reason there is to ascribe to extraordinary convulsions the
excavations which are made by water upon the surface of the earth, will
appear most evidently from the examination of that natural bridge of
which mention is made above, and which is situated in the same ridge
of mountains, far to the south, upon a branch of James's River. Mr
Jefferson gives the following account of it.

"The natural bridge, the most sublime of nature's works, is on the
ascent of a hill, which seems to have been cloven through its length
by some great convulsion. The fissure, just at the bridge, is by some
admeasurements 270 feet deep, by others 205; it is about 45 feet wide at
the bottom, and 90 feet at the top; this of course determines the length
of the bridge, and its height from the water. Its breadth in the middle
is about 60 feet, but more at the ends; and the thickness of the mass
at the summit of the arch about 40 feet. A part of its thickness is
constituted by a coat of e