As regards the main drain, archaeology has indeed shown that it was bricked and vaulted at a late date; but there is no reason for thinking that it began its existence with the masonry that now encloses it. The London Fleet and Tyburn suggest the opposite. The most recent volume on the subject is emphatic on this point. “The earliest Roman sewer consisted undoubtedly of a natural watercourse, the channel of which was widened and deepened[1264].” “There is no doubt that the first attempts at artificial drainage date from the regal period. The first part of the city to be drained was the Forum valley[1265].” [Sidenote: and the Forum graves show only (_pace_ Pais) that the cemetery was secularized not later than late in the regal period.] Those who maintain a post-regal date for the building of the Forum base their arguments on the finds of pottery in the Forum graves. The finds have been numerous and their evidence is valuable, and it is necessary briefly to review it. The latest style of pottery found in these graves is the Proto-Corinthian. This very distinctive and widely distributed pottery[1266] has been the subject of much controversy as regards its place of origin, but its chronology is well established. It flourished in the seventh century: during the sixth it persisted in a few stereotyped forms, of which at least two[1267] lived on in a degraded form into the fifth. Vases of this style quoted by Boni[1268] as coming from two of the latest graves in the Forum are illustrated in the _Notizie degli Scavi_[1269] (fig. 36). Both the vases illustrated might well be seventh century. At Rhitsona in Boeotia the types were completely obsolete by the middle of the sixth century, not one example occurring among some 2500 vases excavated from graves of the latter half of the century. This mass of pottery included about 150 Proto-Corinthian vases, but the number is divided about equally between kothons like _J.H.S._ XXXI. p. 75, fig. 4, and small skyphoi such as _J.H.S._ XXIX. p. 319, fig. 7, no. 9, with just two or three pyxides like _J.H.S._ XXIX. p. 312, fig. 2, no. 8. In the Forum graves there are a certain number of vases of other styles that cannot be dated so accurately as the Proto-Corinthian but suggest on stylistic grounds a somewhat later date. None of them however would naturally be put later than towards the end of the sixth century, and very few so late as that[1270]. Occasional burials of a later date would be evidence for a later conversion from cemetery to Forum only if intramural burials were unknown in Rome. As a matter of fact there is explicit evidence that they took place[1271]. [Illustration: Fig. 36. Proto-Corinthian vase found in the Roman Forum.] [Sidenote: Views on the historicity of Servius Tullius.]