ave never had an opportunity of studying the effects of these
tones upon rocks of porphyry; but the beautiful color of that rock in
its interior substance has rendered it one of the favorite materials of
the architects of all ages, in their most costly work. Not that all
porphyry is purple; there are green and white porphyries, as there are
yellow and white roses; but the first idea of a porphyry rock is that it
shall be purple,--just as the first idea of a rose is that it shall be
red. The purple inclines always towards russet[44] rather than blue, and
is subdued by small spots of grey or white. This speckled character,
common to all the crystalline rocks, fits them, in art, for large and
majestic work; it unfits them for delicate sculpture; and their second
universal characteristic is altogether in harmony with this consequence
of their first.

Their second characteristic. _Toughness._

Sec. 16. This second characteristic is a tough hardness, not a brittle
hardness, like that of glass or flint, which will splinter violently at
a blow in the most unexpected directions; but a grave hardness, which
will bear many blows before it yields, and when it is forced to yield at
last, will do so, as it were, in a serious and thoughtful way; not
spitefully, nor uselessly, nor irregularly, but in the direction in
which it is wanted, and where the force of the blow is directed--there,
and there only. A flint which receives a shock stronger than it can
bear, gives up everything at once, and flies into a quantity of pieces,
each piece full of flaws. But a piece of granite seems to say to itself,
very solemnly: "If these people are resolved to split me into two
pieces, that is no reason why I should split myself into three. I will
keep together as well as I can, and as long as I can; and if I must fall
to dust at last, it shall be slowly and honorably; not in a fit of
fury." The importance of this character, in fitting the rock for human
uses, cannot be exaggerated: it is essential to such uses that it should
be hard, for otherwise it could not bear enormous weights without being
crushed; and if, in addition to this hardness, it had been brittle, like
glass, it could not have been employed except in the rudest way, as
flints are in Kentish walls. But now it is possible to cut a block of
granite out of its quarry to exactly the size we want; and that with
perfect ease, without gunpowder, or any help but that of a few small
iron wed