"We must also decide how we shall construct the floors. In Paris, at the present day, they construct all the floors with joists of double T iron, and for bearings of 16 to 20 feet they take iron 4 to 6 inches in vertical section. They pug these iron joists - placed about 28 inches apart, and connected at intervals of about a yard, by iron tie-bars lin. square - with plaster concrete. This is no bad method, cer tainly; but here we have neither the iron joists, which are so easily procured at the great centres, nor the plaster-of-Paris, which is perhaps too lavishly used in the capital, but which is nevertheless an excellent material when it is properly em ployed, especially for the interior. We must construct the floors with wood. But I have already told you that tim bers which have not been soaked for some time, and which have been cut scarcely two years, decay very rapidly when enclosed, chiefly in their bearings, that is their extremities built in the walls. To prevent our floors giving us anxiety respecting their durability, we must leave the timbers visi ble, and not build them in the walls. We will, therefore, adopt the system of bearers attached to the walls to receive the bearings of the joists; and as we have small oak trunks, we will content ourselves with squaring them on two faces, and place them diagonally, as I show you here (Fig. 32). For bearings of i6 to zo feet, which are the largest we have, timbers 7 inches square will be sufficient. If we think them insufficient we will put an intermediate beam; that remains to be seen. These joists, diagonally placed, present moreover their maximum of resistance to deflection. We will place them at 20 inches from centre to centre. Their bearings will be in the notches made in the bearers, as marked at A, and the soffits - which are the spaces between the joists - will be made with bricks placed flat-ways, overlaid with mortar and plastered beneath. We may decorate these ceilings with line painting, which renders them light and agreeable to the sight, as at H. Joists thus placed do not present internal angles difficult to keep clean, and among which spiders spin their webs. A dust with a soft brush readily cleans these soffits.
"As to the bearers B, (placed against the wall, as section c shows), they will be supported by corbels, D, a yard apart at most, and by cramps, I, to prevent these timbers from giving out. This arrangement will take the place of those
cornices run in plaster, which are of no use, and which we could not get executed properly in this neighbour hood, where we have no good workmen in plaster. When partitions above have to be supported, we will put a special joist, the section of which I have sketched for you at E, composed of two pieces, a and b, with an iron plate be tween them - the whole fastened together by iron pins at intervals. Joists like this are perfectly rigid.
"As the joists rest on bearers, we have no need to trouble ourselves about the windows, but we shall require trimmers at the chimney-breasts and under the hearths, and - to re ceive these trimmers - trimmer-joists. You will easily see that it would be dangerous to lay pieces of wood under fire places. Accordingly, we place on the two sides of the jambs of these fire-places, at a distance of 12 inches from the hearth-stones, stronger joists, which receive at 32 or 36 inches from the wall - to clear the width of the fire-place a piece called a trimmer, into which the joists are tenoned.
"For the trimmer-joists we will take the type previously indicated at E; we shall strengthen (Fig. 33) this beam in its bearing with a block, D, resting on a strong stone corbel. bind the two pieces, E and D, by an iron strap, F, and frame the trimmer by a tenon, H, in the mortise G. This trimmer will receive, like the bearers, the ends of the joists at T. The space, G K, will be the under side of the hearth of the fire-place above; it will be 32 inches wide, and will be bedded with brick, laid on tie-pieces of iron, L. These trimmer-joists, E, will have to be let into the wall about 4 inches, to render them firm and bind the structure; but in the neighbourhood of the flues we have no reason to fear the effect of damp on the wood. To sum up, this is the appearance of these joists and trimmers underneath the fire-places (Fig. 34)." All this, it must be confessed, appeared rather strange to Paul, accustomed as he was to the invariable smooth white ceiling, and who had never suspected that such level sur faces could hide such a framework.