Apart from absolute chronology, what unequivocal evidence can archaeology provide that early Rome was ruled by kings? The ideal evidence would be an inscription, and one was discovered in 1899 in the Forum near the Comitium, where, in the open air in front of the Senate House, the popular assembly met. The inscription is called the _lapis niger_ stele, because it lies under a later pavement of black marble (_lapis niger_), now preserved under a deplorable corrugated iron roof. But the stone on which it is carved is not marble but tufa, identified as having come from the quarries of Grotta Oscura in the territory of Veii, some nine miles north of Rome. On the various kinds of tufa or volcanic stone in use in early Rome there hangs a tale. In 1924 an American, Tenney Frank, published an epoch-making study of Roman building materials in which he put the dating of Roman monuments on a firmer basis by distinguishing several different kinds of tufa used by Roman builders at successive dates. Subsequent studies have blurred the dividing lines and shown the possibility of overlap, but Frank’s nice eye for discriminating tufas has revolutionized the architectural history of the Roman Republic. The following table illustrates Frank’s methods: ---------------------------------------------------------------------- Type Characteristics Quarries Where used ---------------------------------------------------------------------- Cappellaccio flaky dark Rome Capitoline temple grey ash (509 B.C.) Grotta Oscura friable greyish 2½ mi. N. of Forum stele, yellow Prima Porta “Servian” Wall, Tullianum (prison) Fidenae flecked black Castel Giubileo, Castrum, Ostia fragments 5 mi. N. (338 B.C.) (scoriae) of Rome Argentina Temple A (ca. 200 B.C.) peperino peppered; can Marino (Alban Tomb of be carved Hills 11 mi. Scipios (early SE) 3rd cent.) Altar, Argentina C (ca. 186 B.C.) sperone coarse-grained Gabii Milvian Bridge brown (12 mi. E) (109 B.C.) Monteverde reddish, olive Across Tiber Sullan pavement streaks nr. _Lapis niger_