ree of incrustation, from the mere
setting of the larger and more compact stones by preference at the
outside of the wall, to the miserable construction of that modern brick
cornice, with its coating of cement, which, but the other day, in
London, killed its unhappy workmen in its fall.[30] But just as it is
perfectly possible to have a clear idea of the opposing characteristics
of two different species of plants or animals, though between the two
there are varieties which it is difficult to assign either to the one or
the other, so the reader may fix decisively in his mind the legitimate
characteristics of the incrusted and the massive styles, though between
the two there are varieties which confessedly unite the attributes of
both. For instance, in many Roman remains, built of blocks of tufa and
incrusted with marble, we have a style, which, though truly solid,
possesses some of the attributes of incrustation; and in the Cathedral
of Florence, built of brick and coated with marble, the marble facing is
so firmly and exquisitely set, that the building, though in reality
incrusted, assumes the attributes of solidity. But these intermediate
examples need not in the least confuse our generally distinct ideas of
the two families of buildings: the one in which the substance is alike
throughout, and the forms and conditions of the ornament assume or prove
that it is so, as in the best Greek buildings, and for the most part in
our early Norman and Gothic; and the other, in which the substance is of
two kinds, one internal, the other external, and the system of
decoration is founded on this duplicity, as pre-eminently in St. Mark's.

Sec. XXV. I have used the word duplicity in no depreciatory sense. In
chapter ii. of the "Seven Lamps," Sec. 18, I especially guarded this
incrusted school from the imputation of insincerity, and I must do so
now at greater length. It appears insincere at first to a Northern
builder, because, accustomed to build with solid blocks of freestone, he
is in the habit of supposing the external superficies of a piece of
masonry to be some criterion of its thickness. But, as soon as he gets
acquainted with the incrusted style, he will find that the Southern
builders had no intention to deceive him. He will see that every slab of
facial marble is fastened to the next by a confessed _rivet_, and that
the joints of the armor are so visibly and openly accommodated to the
contours of the substance within, that