Decorum or Decency, is that which makes the Aspect of the Fabrick so correct, that there is nothing that is not approv'd of, and founded upon some Authority. It teaches us to have regard to three things, which are, _Design_, _Custom_ and _Nature_. The Regard to Design makes us chuse for Example, other Dispositions and Propertions for a Palace than for a Church. The Respect we have to Custom, is the Reason, for Example, That the Porches and Entries of Houses are adorned, when the Inner Parts are Rich and Magnificent. The Regard we have to the Nature of Places, makes us chuse different Prospects for different Parts of the Fabrick, to make them the wholsomer and the more convenient: For Example, the Bed-Chambers and the Libraries are exposed to the Morning Sun; the Winter Apartments, to the West; the Closets or Pictures and other Curiosities, which should always have equal Light, to the North. Oeconomy teaches the Architect to have regard to the Expences that are to be made, and to the Quality of the Materials, near the Places where he Builds, and to take his Measures rightly for the Order and Disposition; _viz._ to give the Fabrick a convenient Form and Magnitude. These Eight Parts, as we have said, have a Relation to the Three first, _viz._ _Solidity_, _Convenience_, _Beauty_, which suppose, _Order, Disposition_, _Proportion_, _Decorum_ and _Oeconomy_. This is the reason that we divide this first Part only into Three Chapters; the first is of the Solidity; the second of the Convenience; the third of the Beauty of the Fabrick. CHAP. II. _Of the Solidity of Buildings._ ARTICLE I. _Of the Choice of Materials._ The Materials of which _Vitruvius_ speaks are, Stone, Brick, Wood, Lime, and Sand. All the Stones are not of one sort, for some are soft, some harder, and some extreamly hard. Those that are not hard are easily cut, and are good for the Inner Parts of the Buildings, where they are cover'd from Rain and Frost which brings them to Powder, and if they be made use of in Buildings near the Sea, the Salt Particles of the Air and Heat destroys them. Those that are indifferently hard, are fit to bear Weight; but there are some sorts of them, that easily crack with the heat of the Fire. There is likewise another sort of Stone, which is a kind of Free-Stone; some are Red, some Black, and some White, which are as easily cut with a Saw as Wood. The best Bricks are those which are only dry'd and not baked in the Fire; but there are many Years required to dry them well: and for this Reason, at _Utica_, a City of _Africa_, they made a Law, That none should make use of Bricks which had not been made five Years: For these sort of Bricks, so dry'd, had their Pores so close in their Superficies, that they would swim upon Water like a Pumice-Stone; and they had a particular Lightness, which made them very fit for all sorts of Buildings.