After the operation of scraping and rubbing dry, they retired into or remained in the tepidarium until they thought it prudent to encounter the open air. But it does not appear to have been customary to bathe in the water, when there was any, which was not the case at Pompeii nor at the Baths of Hippias, either of the tepidarium or frigidarium; the temperature only of the atmosphere in the two chambers being of consequence to break the sudden change from the extreme hot to cold. Returning now to the frigidarium, 8, which according to the directions of Vitruvius has a passage, 14, communicating with the mouth of the furnace, _e_, and passing down that passage we reach the chamber, 15, into which the præfurnium projects, and which has also an entrance from the street, B, appropriated to those who had charge of the fires. There are two stairways in it, one leading to the roof of the baths, and the other to the coppers which contained the water. Of these there were three, one of which contained the hot water, caldarium; the second, the tepid, tepidarium; and the last, the cold, frigidarium. The warm water was introduced into the warm bath by means of a conduit pipe, marked on the plan, and conducted through the wall. Underneath the caldarium was placed the furnace which served to heat the water and give out streams of warm air into the hollow cells of the hypocanstum. These coppers were constructed in the same manner as is represented in the engraving from the Thermæ of Titus; the one containing hot water being placed immediately over the furnace, and as the water was drawn out from these it was supplied from the next, the tepidarium, which was already considerably heated, from its contiguity to the furnace and the hypocaust below it, so that it supplied the deficiency of the former without materially diminishing its temperature; and the space in the last two was in turn filled up from the farthest removed, which contained the cold water received direct from the square reservoir behind them. Behind the coppers there is another corridor, 16, leading into the court, 17, appropriated to the servants of the baths, and which has also the conveniences of an immediate communication with the street by the door, C.