The contrivance whereby this was effected is curious, and is clearly shewn in the figures here given, in the former of which we see the flat surface of the tiles which lined the Thermal chamber, with their fastenings at each corner; in the latter, a vertical section of the same chamber, shewing the manner in which the tiles were attached to the wall.
Adjoining to the caldarium was the tepidarium, which, as its name implies, admitted the use of only a moderate temperature, a flue passed under it connected with those of the caldarium and hypocaust, but its real warmth proceeded from a large brazier of bronze lined with iron, at one end of it[1], in which the boilers were placed, as exhibited in the figure here given. It has, however, been conjectured that in the great baths at Rome some better system for heating must have been adopted. The supply of water was conveyed by an aqueduct into a cistern placed above them, and open to the air, so that it might be warmed as much as possible by the sun, before it was admitted to the boilers.
In some cases, the water was heated by earthenware pipes, which passed through them full of hot air from the hypocaust. Of this arrangement a more precise notion may be obtained from the woodcut in the following page.
Many practical difficulties co-exist with such a system of heating, and in the cases of the largest Thermæ the radiation was probably so great as to
- ↑ See engraving, Dict. of Antiq., p. 139.
