as is commonly supposed. The Romans frequently used concrete walls in their aqueduct bridges and other constructions. The cement used was of extraordinary hardness, and has, I believe, never been surpassed, even if equalled, in later times. It might be called the "cement of the Romans," as the term "Roman cement" is now commonly applied to a very inferior article. In making concrete columns, the Romans adopted the practice of inserting layers of their flat bricks, which we should perhaps call tiles, at intervals, and they faced the surface with stones, generally disposed after the fashion known as opus reticulatum. This consisted in placing small cubical blocks of stone against the surface of the concrete, so that the sides of the exposed faces were not vertical and horizontal, but the diagonals were, thus giving the appearance of network, or of a chess-board set up on one corner. These devices assisted greatly in protecting the structure from the weather, and from rough usage. Such walls may

also be very well faced with tiles of various kinds.

Chimney flues. These should be as straight as possible. They should be separate from one another-a matter very often not attended to-and they are better lined with pipes, as these are much more easily cleaned, an updraught is more readily established in them, and they completely disconnect the flue from the structure of the house, and so help to prevent destruction by fire.

It is important that the chimneys should be higher than the surrounding buildings, so that the wind may pass freely over them, and that they may not be sheltered from

its action in any direction whatever. If this is not the case, there will be a down draught in the chimneys when the wind is in a certain direction, and the more the chimneys are sheltered by high buildings the more chances there are of down draughts in them. If necessary, an iron or zinc pipe called a " tall-boy" may be placed on the top of the brickwork, to increase the length of the flue. This is sometimes even carried up adjoining buildings, and is, as a general rule better without a cowl of any kind on the top of it, as will be further explained in the next lecture.

Flooring.-Fire proof floors are most desirable. They may be made of concrete or brick arches between iron girders, in which case there is no space between the flooring of one room and the ceiling of the room below. When timber is used, it should be dry and well-seasoned, with sound boarding and pugging, to ensure separation between the rooms, and to prevent either water leaking from the floor to the ceiling below, or air passing from the room below to that above. Good flooring evidently serves to protect the ceilings of the rooms below. Where there is space between the flooring and the ceiling, and still more especially where a wooden flooring is placed over a concrete or other foundation laid on the ground, it is necessary to provide for ventilation of the space below the flooring. This is usually done by placing a perforated iron grating, instead of a brick, here and there in the outer walls, so that air can pass freely in or out below the floors. For this purpose bricks with conical holes through them, (Ellison's patent) would no doubt be found very useful.

The Roof. This may be constructed either of fire-proof materials, or of timber, and in either case may be covered with slate or tiles, or may be thatched; copper or corrugated iron are also used. Sometimes zinc is used on ac

(a.) Section of perforated brick. (b.) Inner surface. (c.) Outer surface.

count of its cheapness, but it is not a good material, as it does not last long. Lead is largely used, especially upon flat roofs, and it is valuable on account of its lasting properties. Where there are eaves, it is important that they should not drip on to the walls, but project, so as to throw the water off. Cornices and all projections should be constructed so as to throw off the rain, or it will run down the walls. If this is not done the walls will be continually damp and dirty. Rain water gutters may be made of lead or iron. They must have a sufficient fall, and shoot directly into the heads of the rain-water pipes. They should be wide enough inside to stand in, so that the snow

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may be cleared out. If this is not done it will accumulate, blocking up the channel, and when the thaw comes the melted snow will work its way through the tiles or slates of the roof, and injure the ceilings below. Rain-water gutters should not be carried through the house from one side to the other, and especially not through bedrooms. Nor should they be carried, as is sometimes done, round the house inside the walls, and through the rooms. A more or less disagreeable smell is frequently noticed in rooms through which rain-water gutters pass. The rainwater pipes should also be outside the house. They should be of iron, well jointed. Galvanised iron ones are preferable; they are only a little more expensive and last much longer. They should either discharge into rain-water tanks, which must be well ventilated, or on to the surface of the ground or area round the house. They should not be directly connected with the drains or sewers. Neither should they be placed with their hoppers or heads just below the bed-room windows, especially if they discharge into a tank.

Large and high houses, especially if standing alone, require to be provided with lightning conductors. Copper ones are better than iron, and need not be so thick. They must be insulated from the walls of the house. by suitable rings of some non-conducting material, and end in some moist place in the soil. In the case of an isolated house it is also a good plan to have a weather

The remark as to the width of gutters does not apply to eavesgutters.

cock on the roof, and connect that with a registering apparatus in the hall. An anemometer is also useful.

Thus far about the construction of the building itself. We now come to finishing off inside. The floors should be covered with boarding-oak bees-waxed being the best, or deal, stained and varnished, may also be used. The joints are better tongued. Parquet flooring, made of teak, may be placed over the whole of the surface, the object being to ensure, as far as possible, a uniform and impervious surface without cracks or badly made joints in which dust may accumulate. This is especially important. Either of these plans is better than the common one of covering the whole floor with a carpet or drugget; when these are used, a border of stained and varnished or polished boards, or of parquet flooring, should be left all round the This has the advantage that dust does not accumulate so readily in the corners, which are more easily swept and cleaned, and the carpet can be taken up at any time to be beaten without moving the furniture which is against the walls. The skirting boards of wooden floors should be let into a groove in the floor. This will serve to prevent draughts coming through, and dust accumulating in the apertures which are invariably formed by the shrinking of the joints and the skirting. Some floors, such as those of halls, greenhouses, &c., are best tiled.

room.

Wall Coverings.-These, like the floors, are better made of impervious materials which can be washed. Tiles form an admirable wall covering, and are moreover a permanent decoration. Various kinds of plastering, with the