71.The luxury of forcing vegetable productions, it would appear, had even been attempted by the Romans. Specularia, or plates of the lapis specularis (talc), we are informed by Seneca and Pliny, could be split into thin plates, in length not exceeding five feet (a remarkable circumstance, since few pieces larger than a fifth of these dimensions are now any where to be met with); and we learn from Columella (lib. xii. cap. 3.), Martial (lib. viii. cap. 14. and 68.), and Pliny (lib. xix. cap. 23.), that by means of these specularia, Tiberius, who was fond of cucumbers, had them in his garden throughout the year. They were grown in boxes or baskets of dung and earth, placed under these plates; which were removed in fine days, and replaced at night. Sir Joseph Banks (Hort. Trans., vol. i. p. 148.) conjectures, from the epigrams of Martial referred to, that both grapes and peaches were forced; and Daines Barrington supposes that the Romans may not only have had hot-houses but hot-walls to forward early productions. Flues, Sir Joseph Banks observes (Hort. Trans., vol. i. p. 147.), the Romans were well acquainted with; they did not use open fires in their houses, as we do, but, in the colder countries at least, they always had flues under the floors of their apartments. Daines Barrington's conjecture, however, rests upon no authority; nor is Sir Joseph Banks's much better, as far as regards forcing grapes and peaches. That the Romans had flues to their dwelling-houses is certain; but hot-houses and hot-walls appear to be of comparatively modern invention. The Romans had no chimneys to their houses. In the time of Seneca they warmed their apartments by stoves built in the earth under the house, and the heat was conveyed from these into the various rooms by means of pipes enclosed in the walls. (Seneca, Epist. 90.) Lysons found the flues, and the fireplace whence they received heat, in the Roman villa he has described in Gloucestershire. Similar flues and fireplaces were also found in the extensive villa lately discovered on the Blenheim estate in Oxfordshire. In Italy, the Romans used flues chiefly for baths or sudatories; and in some of these which we have seen in the disinterred city of Pompeii, the walls round the apartment are flued, or hollow, for the circulation of hot air and smoke.