posed to the influence of the atmosphere, like every other
compound mineral body, and to lose that perfect solidity which we find
in the centre of the mass.

We find the granite masses not only subject to decay from the external
surface, by the decomposition of the feltspar, or the dissolution of
its constituent parts, but also liable to be separated into blocks of
different degrees of regularity, commonly rectangular or approaching to
the rhombic shape. This is the consequence, either of larger veins and
fissures, filled with matter which is still more dissolvable than is the
substance of the granite, or else by imperceptible crevices or cutters,
into which the atmospheric influences gradually insinuate, and form at
last a visible separation.

In examining the tops of granite mountains, or where this rock is
exposed to the weather, we may perceive those two species of decay
proceeding together. The external surface of the stone, where there is a
sufficient mixture of feltspar, is separating into grains which form a
species of sand, being nothing but the particles of granite separating
by means of the decaying sparry part. But a similar progress may be
observed, from the external surface penetrating in lines the mass of
solid rock, and dividing that mass into the rectangular blocks into
which those exposed places are gradually resolved.

Now the tops of all those mountains are formed into an assemblage of
pyramids, declining in height from the central pyramid; and all those
pyramids are again in like manner subdivided into lesser pyramids. But
the smallest of those pyramids are no other than the rectangular blocks
into which those granite masses always separate by the influence of the
atmosphere.

It will now be evident, that those mountains, thus resolving into
separate blocks, must acquire this series of pyramidal constructions;
for, in every particular mass of mountain, there must be a central part,
from which the separated blocks cannot be removed, while those around,
or towards the sides, are detached by the swelling water upon freezing,
and separated from the more central masses which are thus the latest of
being removed.

It is impossible to see this series of pyramidal relics, without at the
same time perceiving that manner of formation, by the gradual resolution
of the solid mass of granite, as it comes to be exposed in succession to
the influences of the atmosphere, which M. de Saussure has termed _les
r