5. The foundation is usually a stone wall, on which the superstructure of the building rests. The most solid basis on which it is placed is rock, or gravel which has never been disturbed; next to these are clay and sand. In loose or muddy situations, it is always unsafe to build, unless a solid basis can be artificially produced. This is often done by means of timber placed in a horizontal position, or by driving wooden piles perpendicularly into the earth; on a foundation of the latter description, the greater part of the city of Amsterdam has been built.
6. The column, or pillar, is the simplest member of a building, although it is not essential to all. It is not employed for the purpose of inclosure, but as a support to some part of the superstructure, and the principal force which it has to resist is that of perpendicular pressure. The column is more frequently employed in public than in private buildings.
7. The wall may be considered the lateral continuation of the column, answering the purposes both of support and inclosure. It is constructed of various materials, but chiefly of brick, stone, and marble, with a suitable proportion of mortar or cement. Walls are also made of wood, by first erecting a frame of timber and then covering it with boards; but these are more perishable materials, which require to be defended from the decomposing influence of the atmosphere, by paint or some other substance.
8. The lintel is a beam extending in a right line from one column or wall to another over a vacant space. The floor is a lateral continuation or connexion of beams, by means of a covering of planks. The strength of the lintel, and, in fact, every other elementary part of a building used as a support, can be mathematically determined by the skilful architect.
9. The arch answers the same purpose as the lintel, although it far exceeds it in strength. It is composed of several pieces of a wedge-like form, and the joints formed by the contact of flat surfaces point to a common centre. While the workmen are constructing the arch, the materials are supported by a centring of the shape of its internal surface. The upper stone of an arch is called the key-stone. The supports of an arch are called abutments; and a continuation of arches, an arcade.
10. The vault is the lateral continuation of an arch, and bears the same relation to it that a wall bears to a column. The construction of a simple vault is the same with that of an arch, and it distributes its pressure equally along the walls or abutments. A complex or groined vault is made by the intersection of two of the common kind. The groined vault is much used in Gothic architecture.
11. The dome, or cupola, is a hemispherical or convex covering to a building or a part of it. When built of stone it is a very strong kind of structure, even more so than the arch, since the tendency of the parts to fall is counteracted by those above and below, as well as by those on each side. During the erection of the cupola, no centring is required, as in the case of the arch.
12. The roof is the most common and cheap covering to buildings. It is sometimes flat, but most commonly oblique, in shape. A roof consisting of two oblique sides meeting at the top, is denominated a pent roof; that with four oblique sides, a hipped roof; and that with two sides, having each two inclinations of different obliquities, a curb or mansard roof. In modern times, roofs are constructed of wood, or of wood covered with some incombustible material, such as tiles, slate, and sheets of lead, tin, or copper. The elementary parts of buildings, as just described, are more or less applicable in almost every kind of architecture.
13. The architecture of different countries has been characterized by peculiarities of form and construction, which, among ancient nations, were so distinct, that their edifices may be identified at the present day even in a state of ruin; and, although nearly all the buildings of antiquity are in a dilapidated state, many of them have been restored, in drawings and models, by the aid of the fragments which remain.
14. The different styles of building which have been recognised by the architect of modern times, are, the Egyptian, the Chinese, the Grecian, the Roman, the Greco-Gothic, the Saracenic, and the Gothic. In all these, the pillar, with its accompaniments, makes a distinguished figure. The following picture has therefore been introduced by way of explanation. The columns are of the Corinthian order of architecture.