Chapter VII. Of the qualities of the ground where foundations ought to be laid

THE foundations are properly called the basis of the fabrick, viz. that part of it under ground which sustains the whole edifice above; and therefore of all the errors that can be committed in building, those made in the foundation are most pernicious, because they at once occasion the ruin of the whole fabrick, nor ean they be rectified without the utmost difficulty. For which reason the architect should apply his utmost diligence in this point; inasmuch as in some places there are natural foundations, and in other places art is required.

We have natural foundations when we build on a chalky soil, which in some degree resembles stone *; for these, without digging or any other assistance from art, are of themselves very strong and sufficient foundations, and capable to sustain any great edifice, either on land or in water,

But when nature does not furnish foundations, then art must be made use of; because the places to build on are sometimes either solid ground, gravel, sand, or a moist and marshy fil. Where it is solid, the foundation need be no deeper than what the quality of the building, and the solidity of the ground hall require (according as the judicious architect hall think proper) and must not exceed the sixth part of the height of the whole edifice, if there are no cellars or subterraneous offices wanted.

Observations made in digging of wells, cisterns, and such like, are of great use, and very much hep us to know the solidity of the ground; as do allo the herbs that spontaneously grow thereon, especially if they are such as spring up only in a hard and firm soil. The solidity may likewise be known by throwing a great weight upon the earth, provided it neither shakes or refounds (which may easily be observed by the help of a drum set upon the ground, it the percussion only gently moves it, without making it found, or without moving the water in vessel set near it:) It may also be judged of by the adjacent places,

But when the place is either Cindy or gravelly, regard must be had whether it be on lind or in the water. If it be on land, that only is to be observed which has before been slid concerning dry ground. But if buildings are to be in rivers, the sand and gravel will be elio-gether useless; because the water, by its continual current and flood, is always shifting their bed: We mutt therefore dig until a firm and solid bottom be found. If that cannot easily be done, let some of the sand and gravel be taken out, and then piles, made of oak, must be driven in, until their ends reach the solid ground, upon which one may build,

But if a building is to be raised upon a boggy soil, then it must be dug out, until firm ground be come at, and so deep therein as is in proportion to the thickness of the walls, and the largeness of the fabrick,

Sound and firm soils, fit to sustain buildings, are of various kinds: For, as ALB rrti well observes, in some places the soil is so hard, that iron can searce cut its way into it, and sometimes still harder; in others blackith or with, which is esteem’d the weakest; some are like chalk, or otherwise soft: But the best is that which is cut with the most labour, and when wet does not dissolve into mud.

No buildings should be erected on ruins before their depth is first known, and whether they are sufficient to sustain the edifice.

Wh en the ground is soft, and sinks very much, as it commonly does in bogs, then piles are to be used, whose length ought to be the eighth part of the height of the walls, “and their thickness the twelfth part of their length, The piles are to be driven so close to one another, as not to leave space for others to come in between, Care must allo be taken to drive them rather with blows frequently repeated, than such as are violent; that so the earth may bind the better to fasten them.

The pilings are to be not only under the outside walls, which are placed upon the canals; but also under those which are placed on the earth, and divide the fabrick: For if the foun-nations of the middle walls are made different from those on the outside, it will often happen, that when the beams are placed by each other in length, and the others over them crossways, the inside walls will sink, and the outside ones, by being piled, will remain unmov; which, besides its being very disagreeable to the sight, will occasion all the walls to open, and ruin the whole edifice, This danger therefore is to be avoided by a trifling expence in piling; for according to the proportion of the walls, the piles in the middle will be smaller than those for the outside.

* There are strictly no proper words in English for Tufa or Scaranto,