[Sidenote: _Lib. 2. Chap. 4._] For to make the right use of Sand, you must first consider what it is to be employ'd in; for if it be Mortar for Plastring, you must not make use of Sand that was lately dug out, for it drys the Mortar too fast, which cracks the Plastring; but quite contrary if it be to be employ'd in Masonry, it must not have been a long time expos'd to the Air, for the Sun and the Moon do so alter it, that the Rain dissolves it, and turns it almost all into Earth. [Sidenote: _Lib. 2. Chap. 5._] The Proportion that Sand and Lime ought to have to make good Mortar, should be three parts of Sand that is dug, or two parts of River-Sand or Sea-Sand against one of Lime, and 'twill be yet much better, if you add to the Sand of the Sea and the River a third part of Tiles well beaten. [Sidenote: _Lib. 7. Chap. 3._] One of the Principal Things that is to be observ'd in making Mortar, is, to mix it well. The Grecian Workmen were so careful of this, that they Tewed it a great while, putting Ten Men to every Vessel wherein they wrought it, which gave so great a hardness to the Mortar, that when any big pieces of Plaster fell off the Old Walls, they made Tables of it. ART. III. _Of the Foundation._ [Sidenote: _Lib. 6. Chap. 11._] The Foundation is the most important part of the Fabrick; for the Faults committed in it cannot be so easily remedied as in other parts. [Sidenote: _Lib. 1. Chap. 5._] To lay the Foundation well, you must dig till you come to solid Ground, and even into the solid as much as is necessary to support the Weight of the Walls; it must be larger below than above the Superficies of the Earth. [Sidenote: _Lib. 3. Chap. 3._] When you have found firm Earth to make it more solid, you must beat it with a Rammer; but if you cannot arrive at solid Earth, but find it still soft and spungy, you must dig as far as you can, and drive in Piles of Alder, Olive, or Oak, a little singed, near together, and fill up the void Places between the Piles with Coal. [Sidenote: _Lib. 1. Chap. 5._] In short, you must make all Masonry with the most solid Stone that can be found for this use. To make the Binding of the Stones the stronger in the Foundation of great Fabricks, you must put Piles of Olive a little singed and placed very thick from one Parement or Course to another, which serves, as it were, for Keys and Braces; for this Wood so prepar'd, is not subject to Worms, and will endure for ever, either in the Earth or in the Water, without the least Damage. [Sidenote: _Lib. 6. Chap. 11._] When you would make Cellars, the Foundations must be much larger; for the Wall that is to support the Earth requires a greater thickness to resist the strong Efforts that the Earth makes against it in Winter, at which time it swells and becomes more heavy by reason of the Water it has drunk up. ART. IV. _Of the Walls._ [Sidenote: _Lib. 4. Chap. 2._]