1. Sand.
The composition of Roman mortar and cement is described under STRUCTURA: we here notice the different kinds
of sand employed,--a subject to which Vitruvius has devoted a chapter
(2.4). He reckons four kinds of pit sand (
fossilis), besides sea and river sand; the black (
nigra), the white (
cana), the red (
rubra), and the
volcanic (
carbunculus: cf. Varr.
L.
L. 1.9, 2). Pliny recognises only the distinctions of sea,
river, and pit sand, not those of colours (
H. N. 36.
§ § 54, 55). In another chapter (2.6) Vitruvius
describes the
pulvis Puteolanus, or
volcanic sand of the
[p. 1.179]neighbourhood of
Vesuvius, as a different material, unaware that it is substantially
identical with that of the Roman Campagna. The modern name
pozzolana is applied indifferently to both.
