"Have you seen whether Branchu has taken care to have the materials extracted from the excavations regularly deposited?" "Yes : but hitherto he has found only thin layers of what he calls rag; but he has them stacked, and tells me they will be very good for foundation walls." "He is right : this rag is liable to injury from frost in the open air, but it is hard, and does very well in cellars; and it makes good strong walling, because it is bedded, - that is, occurs in the natural state in thin parallel layers, 4 to 6 inches thick." "That is just about what he told me; but he added that it swallows up a great deal of mortar, and I did not quite understand what he meant by that." "The fact is this; - the thinner the layers of stone are, the more beds of mortar they require between them; but if you have observed the thin stones in question you will have remarked that they are extremely rough and riddled, with cavities on their beds. There must be plenty of mortar between each course, to fill these rugosities and cavities well: and for that very reason masonry of this kind is excellent, if you are not sparing of mortar; and these rough surfaces adhere to the mortar much better than smooth surfaces could do : they become incorporated with it, and the whole soon forms one solid mass. But then you must not spare lime and sand, and that is why Branchu says this kind of walling swallows up a great deal of mortar." "Branchu also says that he has been finding stone good for making lime, above blocks of building limestone, and asks whether he is to put that aside." "Certainly if the lime-burner at the Mill cannot furnish us with lime, we will make it ourselves; this will not be difficult since we have plenty of firewood from the recent fellings." "Branchu also asked me where he was to put the exca vated earth." "You will tell him to-morrow morning, to have it de posited en cavalier to the right and left of the excavations; we shall want it to level the approaches to the house." "What is a cavalier 1" is an artificial mound of regular breadth and height, so that its solid content can easily be calculated. Thus, when earth is removed from diggings with wheelbarrows, - and this is, as you see, the means we are employing, - we mark out the area this mound is to occupy on the ground, as at A B (Fig. 22), representing the length, and C D the breadth. That done, the point B being farthest from where the excavation is going on, the wheelbarrow men deposit their first loads at B, leaving an inclined embankment not too steep for the barrows to be wheeled up it without too much labour. Thus by degrees an embankment, A E B, is formed. Then, from the middle F half way up the incline A E, they leave a road, a b, 5 feet wide for the barrows to go up and down, and then fill up the triangle, A G F, by inclined layers. Lastly, they fill the triangle, G F E. The road, g D i, remains to be filled up, and the shovellers do this by depositing the soil on the road itself. The mound being thus perfectly regular, its slopes are produced by the run ning down of the soil - that is, they form angles of about 40° with the horizon, according to the nature of the embank ment. The mound being finished, and measuring, say, ro yards long at half its length from 1 to m, and 4 yards wide at half its height from n to b, - multiplying lo yards by 4 yards we get 4o superficial yards at this mean level. Multiplying this number by 2 yards, the height of the mound, we get 8o cubic yards. You know therefore that this quantity of earth has been moved, and consequently, what you have to pay, if your cuttings and embankings are at so much per cubic yard, or what a cubic yard of soil removed costs you if you pay by the day." "This will give us the solid content of the excavation then?" "Not exactly. Earth compressed, - settled down in the natural soil, - occupies a smaller volume than that which, having been moved, leaves many interspaces between the materials of the embankment. Soil when removed is said to increase, more or less. Sea-sand does not increase, while pebbly earth, mixed with vegetable detritus, increases greatly. In your memoranda, therefore, you must take
account of the looseness caused by excavating, to get the solid content of the soil removed; and take the solid content of the mounds when we make use of them, to know the mass of earth we shall have to transport elsewhere." "You will now draw this plan of the cellars to a scale of a quarter of an inch to a foot, so that you may figure the dimensions very legibly where required; then I shall indi cate to you on this plan the points where bedded stone must be placed." "What are bedded stones?" "Dressed stone laid as a foundation is thus designated, and which is only dressed on its beds, - that is to say, which presents no visible faces. Dressed stone has always two beds, which are its horizontal surfaces, one or more faces, which are its exposed surfaces, and its joints, which are its separating surfaces. Thus, let us suppose a corner stone, bearing a pilaster, and having the form indicated here (Fig. 23), the surface abcdef,ghijklare the upper and lower beds. The surfaces a lbg,bgch,cdhi,deij are the exposed faces, and the surfaces efjk,afkl are the joints, as the adjacent stones touch these surfaces. You will easily see that when stones are placed below the sur face, as a foundation, it is not necessary to dress the faces which would be visible only to the moles. This cutting therefore is saved; the stone is left in the rough on its vertical faces, and only those on which it rests are cut. For these bedded stones solid blocks are chosen, which sustain pressure, but which may be very coarse in grain, and even sensible (i.e., liable to be cracked by frost), and which could not be employed in the open air without danger; under ground these stones are preserved from the action of frost. But care must be taken with regard to these stones even more than for those above ground, to place them according to their quarry-bed, and their natural stratified position; otherwise they might be broken or crushed beneath the weight of the masonry above.
"When our plan is drawn, we shall indicate by a par ticular colour the parts where we wish bedded stones to be placed. These will be the angles and the junctions of the walls which sustain the heaviest, pressure relatively to the rest. Between these bedded stones the masonry will be carried up simply in rubble-work.
"The ground being good, we shall content ourselves with foundations only half a yard below the area of the But as soon as we have reached this level, the dressed stones will necessarily have faces visible in the cellars; these stones will therefore not merely be bedded, but faced and jointed. We will not take the best and finest grained, but those that resist pressure best, and which in this district are the coarsest in appearance. We shall put dressed stones in our cellars at the angles, the jambs of the doors and air holes, and in the newels of the stairs.
"But you have enough work for to-day and to-morrow morning.... Ah ! I was forgetting ! If Branchu meets springs, or drippings, that trouble him, inform me, because we must immediately make drains to collect the water. That will determine us as to the level to be given to the bed of our sewer." "What do you mean by the bed?" "It is the part of a channel sluice or a sewer on which the water flows; it is the bottom, which ought to be formed so solidly that the force of the current cannot disturb it. The beds of sewers, therefore, should be made of good flat stones, or, which is still better, of hydraulic cement, when it can be procured, because the water finds its way between the joints of the stones; while, if the cement is properly used, it forms along the whole channel one homogeneous mass perfectly water tight. Besides we take care to give to the bed of a drain a section slightly concave, joining its walls without angles; for water takes ad vantage of angles to effect its work of destruction. Angles, moreover, are not easily cleared out when subterranean channels have to be cleansed. The best form to give to a sewer is the one given here in section (Fig. 24).