In earlier times the rooms were heated by means of braziers, and in one of the Pompeian baths the tepidarium was warmed in this way to the last. A more satisfactory method was devised near the beginning of the first century B.C. by Sergius Orata, a famous epicure, whose surname is said to have been given to him because of his fondness for golden trout (_auratae_). He was the first to plant artificial oyster beds in the Lucrine Lake, and the experiment was so successful that he derived a large income from them; we may assume that he turned an honest penny also by his invention of the 'hanging baths,' _balneae pensiles_, with which his name has ever since been associated. These were built with a hollow space under the floor, the space being secured by making the floor of tiles, two feet square, supported at the corners by small brick pillars (Fig. 88); into this space hot air was introduced from the furnace, and as the floor became warm, the temperature of the room above was evenly modified. This improved method of heating was not long restricted to the floors. As early as the Republican period, the hollow space was extended to the walls by means of small quadrangular flues and by the use of nipple tiles, _tegulae mammatae_, large rectangular tiles with conical projections, about two inches high, at each corner; these were laid on their edges, with the projections pressed against the wall, thus leaving an air space on the inside. In bathing establishments designed for both men and women, the two caldariums were placed near together. There was a single furnace, _hypocausis_, where the water for the baths was warmed; from this also hot air was conveyed through broad flues under the floors of both caldariums, thence circulating through the walls. Through similar flues underneath, the warm air, already considerably cooled, was conveyed from the hollow spaces of the caldariums into those of the tepidariums. In order to maintain a draft strong enough to draw the hot air from the furnace under the floors, the air spaces of the walls had vents above, remains of which may still be seen in some baths. These vents were no doubt sufficient to keep up the draft after the rooms had once been heated; but in order to warm them at the outset a draft fire was needed,--that is, a small fire under the floor at some point a considerable distance from the furnace and near the vents, through which it would cause the escape of warm air, and so start a hot current from the furnace. The place of the draft fire has been found under two rooms of the Pompeian baths; and a similar arrangement has been noted in the case of Roman baths excavated in Germany. The use of the baths varied according to individual taste and medical advice. In general, however, bathers availed themselves of one of three methods.