4I have explained how plastering is executed in dry situations; now I shall give directions for it, that it may be durable in those that are damp. First, in apartments on the ground-floor; a height of three feet from the pavement is to have its first coat of potsherds, instead of sand, so that this part of the plastering may not be injured by the damp. But if a wall is liable to continual moisture, another thin wall should be carried up inside it, as far within as the case will admit; and between the two walls a cavity is to be left lower than the level of the floor of the apartment, with openings for air. At the upper part, also, openings must be left; for if the damp do not evaporate through these holes above and below, it will extend to the new work. The wall is then to be plastered with the potsherd mortar, made smooth, and then polished with the last coat.
2If, however, there be not space for another wall, channels should nevertheless be made, and holes therefrom to the open air. Then tiles of the size of two feet are placed on one side, over the side of the channel, and, on the other side, piers are built, of eight-inch bricks, on which the angles of two tiles may lie, that they may not be more distant than one palm from each other. Over them other tiles, with returning edges, are fixed upright, from the bottom to the top of the wall; and the inner surfaces of these are to be carefully pitched over, that they may resist the moisture; they are, moreover, to have air-holes at bottom, and at top above the vault.
3They are then to be whited over with lime and water, that the first coat may adhere to them; for, from the dryness they acquire in burning, they would neither take that coat nor sustain it, but for the lime thus interposed, which joins and unites them. The first coat being laid on, the coat of pounded potsherds is spread, and the remainder is finished according to the rules above given.
4The ornaments for polished stuccos ought to be used with a regard to propriety, suitable to the nature of the place, and should be varied in their composition. In winter triclinia, neither large pictures nor delicate ornaments in the cornice, under the vault, are to be introduced, because they are soon injured by the smoke of the fire, and of the quantity of lights used therein. In these, above the podium, polished pannels of a black colour are introduced, with yellow or red margins round them. The method of finishing plain as well as enriched ceilings having been described, it will not be amiss, in case any one should wish to know it, to explain the construction of the pavements used in the Grecian winter rooms; which is not only economical but useful.
5The floor of the triclinium is excavated to the depth of about two feet; and after the bottom is well rammed, a pavement of rubbish or potsherds is spread over it, with a declivity towards the holes of the drain. A composition of pounded coals, lime, sand, and ashes, is mixed up and spread thereover, half a foot in thickness, perfectly smooth and level. The surface being then rubbed with stone, it has the appearance of a black pavement. Thus, at their banquets, the liquor that is spilt, and the expectoration which falls on it, immediately dry up; and the persons who wait on the guests, though barefooted, do not suffer from cold on this sort of pavement.