y monument in the whole
island left us by the Romans, that _time_ hath not injured.

The philosophical traveller may make some curious observations in the
line of agriculture, yet in its infancy.

The only growth upon this wild, is gorse and ling: The vegetation upon
the road and the adjacent lands, seem equal: The pits are all covered
with a tolerable turf.

As this road has been made about 1720 years, and, as at the time of
making, both that and the pits must have been surfaces of neat gravel;
he will be led to examine, what degree of soil they have acquired in
that long course of years, and by what means?

He well knows, that the surface of the earth is very far from being a
fixed body: That there is a continual motion in every part, stone
excepted: That the operations of the sun, the air, the frost, the dews,
the winds, and the rain, produce a constant agitation, which changes the
particles and the pores, tends to promote vegetation, and to increase
the soil to a certain depth.

This progress is too minute for the human eye, but the effects are
visible. The powers above mentioned operate nearly as yeast in a lump of
dough, that enlivens the whole. Nature seems to wish that the foot would
leave the path, that she may cover it with grass. He will find this
vegetative power so strong, that it even attends the small detached
parts of the soil where-ever they go, provided they are within reach of
air and moisture: He will not only observe it in the small pots,
appropriated for garden use, but on the tops of houses, remote from any
road, where the wind has carried any small dust. He will also observe it
in cracks of the rocks; but in an amazing degree in the thick walls of
ruined castles, where, by a long course of time, the decayed materials
are converted into a kind of soil, and so well covered with grass, that
if one of our old castle builders could return to his possessions, he
might mow his house as well as his field, and procure a tolerable crop
from both.

In those pits, upon an eminence, the soil will be found deep enough for
any mode of husbandry. In those of the vallies, which take in the small
drain of the adjacent parts, it is much deeper. That upon the road,
which rather gives than receives any addition from drain, the average
depth is about four inches.

The soil is not only increased by the causes above, but also by the
constant decays of the growth upon it. The present vegetable generation
falling