y, and again pebbly; in other places the material is sandy; in a
word, the properties of the soil are as different and unlike as are the
various countries. In particular, it may be observed that sandpits are
hardly ever lacking in any place within the districts of Italy and
Tuscany which are bounded by the Apennines; whereas across the Apennines
toward the Adriatic none are found, and in Achaea and Asia Minor or, in
short, across the sea, the very term is unknown. Hence it is not in all
the places where boiling springs of hot water abound, that there is the
same combination of favourable circumstances which has been described
above. For things are produced in accordance with the will of nature;
not to suit man's pleasure, but as it were by a chance distribution.

6. Therefore, where the mountains are not earthy but consist of soft
stone, the force of the fire, passing through the fissures in the stone,
sets it afire. The soft and delicate part is burned out, while the hard
part is left. Consequently, while in Campania the burning of the earth
makes ashes, in Tuscany the combustion of the stone makes carbuncular
sand. Both are excellent in walls, but one is better to use for
buildings on land, the other for piers under salt water. The Tuscan
stone is softer in quality than tufa but harder than earth, and being
thoroughly kindled by the violent heat from below, the result is the
production in some places of the kind of sand called carbuncular.

[Illustration: TRAVERTINE QUARRIES ON THE ROMAN CAMPAGNA

1. 2. Ancient quarries. 3. A similar modern quarry.

The top of the rock shows the original ground level. The present ground
level shows the depth to which the rock has been removed.]

CHAPTER VII

STONE

1. I have now spoken of lime and sand, with their varieties and points
of excellence. Next comes the consideration of stone-quarries from which
dimension stone and supplies of rubble to be used in building are taken
and brought together. The stone in quarries is found to be of different
and unlike qualities. In some it is soft: for example, in the environs
of the city at the quarries of Grotta Rossa, Palla, Fidenae, and of the
Alban hills; in others, it is medium, as at Tivoli, at Amiternum, or Mt.
Soracte, and in quarries of this sort; in still others it is hard, as in
lava quarries. There are also numerous other kinds: for instance, in
Campania, red and black tufas; in Umbria, Picenum, and Venetia, white
tu