ep the same height
as the stucco; the motion caused by their shrinking prevents them from
adhering to it, and they are separated from their union with it. Hence
the stucco, no longer joined to the core of the wall, cannot stand by
itself because it is so thin; it breaks off, and the walls themselves
may perhaps be ruined by their settling. This is so true that at Utica
in constructing walls they use brick only if it is dry and made five
years previously, and approved as such by the authority of a magistrate.

3. There are three kinds of bricks. First, the kind called in Greek
Lydian, being that which our people use, a foot and a half long and one
foot wide. The other two kinds are used by the Greeks in their
buildings. Of these, one is called [Greek: pentadoron], the other
[Greek: tetradoron]. [Greek: Doron] is the Greek for "palm," for in
Greek [Greek: doron] means the giving of gifts, and the gift is always
presented in the palm of the hand. A brick five palms square is called
"pentadoron"; one four palms square "tetradoron." Public buildings are
constructed of [Greek: pentadora], private of [Greek: tetradora].

4. With these bricks there are also half-bricks. When these are used in
a wall, a course of bricks is laid on one face and a course of
half-bricks on the other, and they are bedded to the line on each face.
The walls are bonded by alternate courses of the two different kinds,
and as the bricks are always laid so as to break joints, this lends
strength and a not unattractive appearance to both sides of such walls.

[Illustration: VITRUVIUS' BRICK-BOND ACCORDING TO REBER]

In the states of Maxilua and Callet, in Further Spain, as well as in
Pitane in Asia Minor, there are bricks which, when finished and dried,
will float on being thrown into water. The reason why they can float
seems to be that the clay of which they are made is like pumice-stone.
So it is light, and also it does not, after being hardened by exposure
to the air, take up or absorb liquid. So these bricks, being of this
light and porous quality, and admitting no moisture into their texture,
must by the laws of nature float in water, like pumice, no matter what
their weight may be. They have therefore great advantages; for they are
not heavy to use in building and, once made, they are not spoiled by bad
weather.

CHAPTER IV

SAND

1. In walls of masonry the first question must be with regard to the
sand, in order that it may be fit