difficult to
walk over, but the pieces touch each other in so few points, and suffer
the water to run so easily and so far through their cavities, that it
takes a long series of years to enable them either to settle themselves
firmly, or receive the smallest covering of vegetation. Where the
substance of the stone is soft, it may soon be worn down, so that the
irregular form is of less consequence. But in the hard crystallines,
unless they had a tendency to break into flattish fragments, their ruin
would remain for centuries in impassable desolation. The flat shape of
the separate pieces prevents this; it permits--almost necessitates--their
fitting into and over each other in a tolerably close mass, and thus they
become comparatively easy to the foot, less permeable to water, and
therefore retentive both of surface moisture and of the seeds of
vegetation.

3. Security on declivities.

Sec. 9. There is another result of nearly equal importance as far as
regards the habitableness of the hills. When stones are thrown together
in rounded or massy blocks, like a heap of hazel nuts, small force will
sometimes disturb their balance; and when once set in motion, a
square-built and heavy fragment will thunder down even a slightly
sloping declivity, with an impetus as unlikely to be arrested as fatal
in its increase. But when stones lie flatly, as dead leaves lie, it is
not easy to tilt any one of them upon its edge, so as to set it in
motion; and when once moved, it will nearly always slide, not roll, and
be stopped by the first obstacle it encounters, catching against it by
the edge, or striking into the turf where first it falls, like a
hatchet. Were it not for the merciful ordinance that the slaty
crystallines should break into thin and flattish fragments, the frequent
falls of stones from the hill sides would render many spots among the
greater mountain chains utterly uninhabitable, which are now
comparatively secure.

4. Tendency to form the loveliest scenery.

Sec. 10. Of the picturesque aspects which this mode of cleavage produces in
the mountains, and in the stones of the foreground, we shall have to
speak presently; with regard to the uses of the materials it is only
necessary to note farther that these slaty rocks are of course, by their
wilful way of breaking, rendered unfit for sculpture, and for nearly all
purposes of art; the properties which render them convenient for the
peasant in building his cotta