air, a moderate amount of moisture, and only a small amount of
the earthy, are composed of a mixture which is proportionately rather
light, and so they are of great service from their stiffness. Although
on account of the mixture of the earthy in them they are not hard, yet
their loose texture makes them gleaming white, and they are a convenient
material to use in carving.

10. The alder, which is produced close by river banks, and which seems
to be altogether useless as building material, has really excellent
qualities. It is composed of a very large proportion of air and fire,
not much of the earthy, and only a little moisture. Hence, in swampy
places, alder piles driven close together beneath the foundations of
buildings take in the water which their own consistence lacks and remain
imperishable forever, supporting structures of enormous weight and
keeping them from decay. Thus a material which cannot last even a little
while above ground, endures for a long time when covered with moisture.

11. One can see this at its best in Ravenna; for there all the
buildings, both public and private, have piles of this sort beneath
their foundations. The elm and the ash contain a very great amount of
moisture, a minimum of air and fire, and a moderate mixture of the
earthy in their composition. When put in shape for use in buildings they
are tough and, having no stiffness on account of the weight of moisture
in them, soon bend. But when they become dry with age, or are allowed to
lose their sap and die standing in the open, they get harder, and from
their toughness supply a strong material for dowels to be used in joints
and other articulations.

12. The hornbeam, which has a very small amount of fire and of the
earthy in its composition, but a very great proportion of air and
moisture, is not a wood that breaks easily, and is very convenient to
handle. Hence, the Greeks call it "zygia," because they make of it yokes
for their draught-animals, and their word for yoke is [Greek: zyga].
Cypress and pine are also just as admirable; for although they contain
an abundance of moisture mixed with an equivalent composed of all the
other elements, and so are apt to warp when used in buildings on account
of this superfluity of moisture, yet they can be kept to a great age
without rotting, because the liquid contained within their substances
has a bitter taste which by its pungency prevents the entrance of decay
or of those little creatu