HISTORY OF WARMING AND VENTILATING ROOMS.

423

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 sur- face of the tiles which lined the Thermal chamber, with their fasteninffs at each corner ; in the lat- ter, a vertical section of the same chamber, shewing tlie manner in which the tiles were attached to the wall. Adjoining to the calda- rium 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 pro- ceeded from a large brazier of bronze lined with iron, at one end of it ^, in which the boilers were placed, as exhibited in the figure here given. It has, h(jL'M_T, hcL'ii roiij. etur(;(l lluil iu llic ^-rcal baths at lium s .i,. in U.'i' 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. Manj' practical difficulties co-exist with such a system of heating, and in the cases of the largest Thermie the radiation was probably so great as to ^ See engraving, Diet, of Antiq., p. 130. 3 I