As the British thermæ is at present in a state of infancy, the question of construction, in reference to the threefold condition, of size of apartment, degree of ventilation and temperature, and materials, is before us for inquiry and research. The common plaster walls of Mr. Witt's Calidarium answer perfectly: they are not too hot for the naked skin, as a glazed or polished material would be; and they admit of cleansing by water, whenever necessary. The red and blue earthen tiles of his bath give a pleasant holding to the soles of the feet on account of their roughness, and with the intramural position of the flue never become too hot. Glazed tiles, although more elegant in appearance, are too hot for contact with the skin, and require, consequently, to be trodden on with wooden clogs; moreover, when at all moistened, they are slippery and dangerous. Therefore, so far as our present means of information go, it would appear that the more economical materials of construction answer in every way the best. We are, however, still open to instruction on these points, as well as in many others appertaining to the bath, and we shall probably be doing best to adhere as closely as possible to the Turkish model. Can the furnace, as at present described, be improved? What combustible material would be the most economical; taking into consideration the questions of price, of rapidity of combustion and of deposition of soot in the flue, requiring more or less frequent cleansing? The flue in Mr. Witt's bath is constructed of galvanized iron plate, and is square in form. This flue answers very well, but Mr. Witt does not approve of iron, because in a hot dry atmosphere particles of the metal are thrown off and mingle with the air. The best material for the construction of the flue is earthen tiles or bricks; probably pipes fitting end to end may, with some modification, be made to answer the purpose, but heretofore they have been found to split with the heat. Then, in the case of building a bath, the relative value of bricks, and especially of hollow bricks, and pierced bricks, and bricks with a surface finish, come under consideration. Immediately over the fine passing around the floor of the Calidarium is a wooden seat; and over the masonry of the furnace, a wooden step and platform affording additional sitting room. On the platform is a wooden couch, shaped like a straddling letter W, called the _dureta_ from the hardness of its material, but in reality forming a most pleasant and agreeable couch, as the angles of the couch correspond with the joints of the body when in a reclining position. The dureta was borrowed by the Emperor Augustus from Spain, or rather from Morocco through Spain,[15] and contributes greatly to the luxury of the bath. [15] "Pillars of Hercules."