SUDATORIUM  , the

term in architecture for the vaulted sweating-room (sudor, sweat) of the Roman thermae, referred to in Vitruvius (v . 2), and there called the concamerata sudatio . In order to obtain the great heat required, the whole wall was lined with vertical terra-cotta flue pipes of rectangular section, placed side by side, through which the hot air and the smoke from the suspensura passed to an exit in the roof .