FOUNDATIONS. This term is applied to the excava tions made in the ground for the base of a building. The trenches should be sunk till they arrive at firm soil or solid rock ; and in large buildings the ground should be further proved by digging pits, or boring to a consi derable depth. If the ground be rather soft or loose, but tolerably firm, pieces of oak, termed sleepers, are laid across the trench, about two feet distant from each other, their lengths being about two feet more than the bottom of the intended wall, and the spaces between them are filled with dry stone rubbish or iron cinders well ram med. Over these sleepers, planks arc laid to a breadth somewhat exceeding that of the masonry, and are spiked to the sleepers; and this operation must be extended to all the walls, external and internal, that the whole edifice may have an equal bearing. if the ground be very soft and loose, wooden piles must be driven to secure the planking. They should be of a sufficient length to reach the solid ground, and be driven as close together as prac ticable. Their thickness should vary from being about one-sixth of their length in short piles, to one-twelfth in long ones. Whet c the ground is generally firm, but hav ing some soft spaces, arches may be turned over the lat ter. When the superstructure is to stand on narrow piers, inverted arches should be turned between; if the ground under these is loose, piles and planking must likewise be used. When the foundations are upon slanting ground,
the trenches must have their bottoms cut in rectangular steps. Forced earth is unfit for foundations, and can scarcely be rendered fit by any precaution short of mak ing a sufficient platform, connected with the original un moved ground.
Besides the foregoing application of the term Founda tion) it also indicates the substructure, or bottom of a wall, which consists of one or more °netts or steps on each side of its perpendicular faces. These are denomi nated footings. The breadth of this substructure must be proportioned to the weight of the superstructure, and the nature of the ground. Where the texture of the soil appears to be tolerably equal and firm, and the mate rials of similar specific gravity, the breadth will be as the area of the vertical section passing through the line in which it is measured. For example, suppose a wall 40 feet high and 2 feet thick to have a sufficient foundation at the breadth of 3 feet, what should the breadth of the foundation be, when the wall is 60 feet high and 2i feet thick ? By taking the proportion 40 X 2 : S : : 60 X 21, we shall have 54 feet. In stone walls, the least breadth added to that of the superstructure, is one foot. In clamp situations, charcoal, sand, tarred paper, and Park er's British cement, may all be used with advantage.