Illustrated Companion to the Latin Dictionary/Saxum quadratum

This article incorporates text from a publication now in the public domain: Rich, Anthony (1849). The illustrated companion to the Latin dictionary, and Greek lexicon. p. vi. OCLC 894670115. https://archive.org/details/illustratedcompa00rich. 

SAXUM QUADRATUM. A rock of volcanic formation, termed by the Italian geologists "lithoid tufo" (tufa litoide), the same as that which forms the basis of the Capitoline hill, and which received the name from the rectangular masses into which its natural fissures divide it. All the earlier buildings ascribed to the legendary period of the kings, the underground dungeon of Servius Tullius, the Cloaca Maxima, and the substructions of the Capitolium, are built of this material, which in fact was the only one in use until the introduction of the Appian and Gabian stone, now designated by the name of peperino. It is consequently this which Livy designates by the name of saxum quadratum (vi. 4.), when speaking of the foundations of the Capitoline temple; and the same material is intended (x. 23.) when he says that the road from the Porta Capena to the temple of Mars was paved saxo quadrato; not that the stones were regularly squared, like ashlar, since the Romans always employed polygonal blocks for road paving (see the article and illustration s. VIA), but that the material used was lithoid tufo, instead of silex, which in his time was the usual one. Brocchi, Suolo di Roma.