There remains one large division of Roman glass which I have purposely left to the last. In this are comprised the engraved and sculptured pieces, the bulk of which belong to a late time; indeed we may pass from work of this kind to glass that is purely Byzantine in character without any violent transition. But to return for a moment to examples taken from quite the other end of the series, we have seen that the glass bowls that are associated with Alexandrian-Greek and early Roman times are mostly finished by a cutting-tool on some kind of lathe. In the case of the bowl of white glass from Canosa in the British Museum, closely imitating in form the well-known _scyphos_ of the Greek potter, the handles are apparently carved out of a solid mass (cf. p. 46); a very similar bowl in the Charvet collection, said to have come from Cumæ, is illustrated by Froehner. Still more interesting is the large shallow bowl or dish of white glass in our national collection; this is again from a tomb at Canosa. A ring of some twenty spurs, each about half an inch in height, arises from the outer margin; these spurs are carved apparently out of the solid glass. A large rosette cut in low relief, representing a full-blown lotus flower, covers nearly the whole of the surface. With this work we may compare the rosettes, much more rudely carved, it is true, on the base of some very similar bowls of late date from the Rhine country. Of quite a different character is the carving on those earlier vessels of which we may take the well-known Portland vase as a type. Here the delicate sculpture in low relief takes us back to the cameos of the Hellenistic Greeks, which, as we have seen, were often executed in a glass paste. But few specimens of work of this kind have come down to us—some half-dozen in all—and of these only two are perfect. The body of these vases is formed by two or more superimposed layers of glass, of which the outer one, generally of an opaque white, is ground away by the wheel of the engraver, leaving a design in low relief upon a basis of blue or other colour.