HYPOCALTSTUM, (from i;l7o under, and Kavcov to burn,) among the Greeks and Romans, a subterraneous place, in which was a furnace for heating the baths. Another kind of hypocaustum was a sort of kiln to heat their winter parlours.
Several hypocausts have been found amongst the Roman remains still existing in Britain. About three years since, the remains of a portion of a Roman villa were laid open in Lower Thames-street, London, and beneath the floor of one of the rooms was discovered a hypocaust formed of columns about two feet in height, each consisting of fourteen tiles about twelve inches square. These were connected at the top by larger tiles, which formed the superstructure of the floor. Flue-tiles, with varied patterns incised on their surfaces, were likewise tbund amongst the ruins, which originally conveyed warm air up the sides of the building.
More recently, a hypocaust was discovered at Cirencester, and in a most perfect condition, the furnace, which was in existence, still containing some portion of the fuel. In this case, the columns were of two kinds, square and circular, the former being composed of tiles laid one upon the other to the number of ten, and the latter being formed of blocks of stone. Resting upon these pillars were large square tiles, as in the preceding example, and above these a layer of concrete six inches in thickness, on which the pavement was laid. The
room above the hypocaust measured twenty-five feet square, and it is remarkable that the h? pocaust extended only half way underneath, the remaining half of the pavement being laid solid.
Still more recently, the remains of some apartments have been found within a Roman camp at Lynne, Kent. An exten sive hypocaust was discovered under the floor of these apart ments, fimued entirely of layers of large tiles placed at regular intervals, but the pavement had been totally destroyed. Seve ral hollow flue-tiles were also discovered of a similar descrip tion to those above alluded to. These, in all probability, were connected with the hypocaust, and served to convey the hot air from the furnace through the principal apartments of the villa, the hypocausts being used not only for baths, as is by some supposed, but also in the place of fires, and answered an exactly similar purpose to our modern hot-air pipes.
In a hypocaust discovered at Lincoln some few years since, the piers supporting the pavement were all of the circular form.