unted for by Dr. Fleming, in his "Zoology of
the Bass." "The summits and sides of those hills which were occupied by
our ancestors as _hill-forts_," says the naturalist, "usually exhibit a
far richer herbage than corresponding heights in the neighborhood with
the mineral soil derived from the same source. It is to be kept in view,
that these positions of strength were at the same time occupied as
_hill-folds_, into which, during the threatened or actual invasion of
the district by a hostile tribe, the cattle were driven, especially
during the night, as to places of safety, and sent out to pasture in the
neighborhood during the day. And the droppings of these collected herds
would, as takes place in analogous cases at present, speedily improve
the soil to such an extent as to induce a permanent fertility." The
further instance adduced by the Doctor, in showing through what
protracted periods causes transitory in themselves may remain palpably
influential in their effects, is curiously suggestive of the old
metaphysical idea, that as every effect has its cause, "recurring from
cause to cause up to the abyss of eternity, so every cause has also its
effects, linked forward in succession to the end of time." On the bleak
moor of Culloden the graves of the slain still exist as patches of green
sward, surrounded by a brown groundwork of stunted heather. The animal
matter,--once the nerves, muscles, and sinews of brave men,--which
originated the change, must have been wholly dissipated ages ago. But
the effect once produced has so decidedly maintained itself, that it
remains not less distinctly stamped upon the heath in the present day
than it could have been in the middle of the last century, only a few
years after the battle had been stricken.

The vitrification of the rampart which on every side incloses the grassy
area has been more variously, but less satisfactorily, accounted for
than the green luxuriance within. It was held by Pennant to be an effect
of volcanic fire, and that the walls of this and all our other vitrified
strongholds are simply the crater-rims of extinct volcanoes,--a
hypothesis wholly as untenable in reference to the hill-forts as to the
lime-kilns of the country: the vitrified forts are as little volcanic as
the vitrified kilns. Williams, the author of the "Mineral Kingdom," and
one of our earlier British geologists, after deciding, on data which his
peculiar pursuits enabled him to collect and weigh, t