Читать книгу The Art in Ancient Egypt - Perrot Georges - Страница 31

Fig. 69.—The Egyptian "bond."

Upon exterior surfaces, supports take various forms of development which may all be referred to the type which we have defined, namely, the portico. In the interiors the form of support is a logical consequence of the material employed. Whenever the stones which form the roof are too small to bridge over the whole of the space comprised within two walls, they must be made to rest upon intermediate supports; and this necessity springs up in every building of any importance. This very elementary combination fulfils all the requirements of circulation. The number of supports depends upon the number of rows of the flat stones which form the roof. They are sometimes multiplied to such an extent that they remind us of that planting arrangement in our gardens which we call a quincunx.

Fig. 70.—Double-faced wall.

We cannot, however, affirm that the number of supports is invariably decided by the length of the architraves, or of the roofing stones. Some very long monoliths are supported at regular intervals, lest they should break with their own weight or with that put upon them. The walls, architraves, and vertical supports are always far stronger than the mere weight of the roof would require.

Figs. 71, 72.—Elements of the portico.

The following woodcut shows the arrangement of supports, architraves and roof. These simple arrangements constitute a complete system of construction which, belonging exclusively to Egypt, has had results upon which we cannot too strongly insist. Both roof and architraves being horizontal, all the pressure upon the walls is vertical. There is no force tending to thrust the walls outwards nor to affect the immobility of the supports.

Fig. 73.—Egyptian construction, epitomized by Ch. Chipiez.

Consequently, if the proportions of the vertical and horizontal elements of a building, that is to say, its sections, have been skilfully determined, there is in the building itself no latent cause of disruption; its equilibrium is perfect, and can only be destroyed by external physical causes, by long exposure to the weather, by earthquakes, or by the hand of man.[104]

We see then that the first impression caused by the external lines of the architectural monuments of Egypt is confirmed and explained by further study. They are built, as said the Pharaohs themselves, "for eternity." Stability, in a word, in its highest and most simple form is the distinguishing characteristic, the true originality, of Egyptian architecture.

This character is most strongly marked in stone buildings, but it is by no means absent from those built of materials created by human industry. Works in brick form the transition between the construction that we have described and that which we call compact. A stone roof is not often found, and the termination is generally a terrace in which wood is the chief element. In some cases the secondary parts of such edifices, and sometimes the whole of them, are covered in by brick vaults, and maintained by walls of a sufficient thickness.

Although the use of monoliths for roofing purposes was general in Egypt, it must not be thought that the architects of that country were ignorant of the art of covering voids with materials of small size, that is to say, of building vaults. There are numerous examples of Egyptian vaults, some of them of great antiquity, and, moreover, the Egyptian builders constructed their vaults after a method of their own. In spite of the facilities which they afforded, they played, however, but a secondary rôle in the development of art. They were never used in the buildings to which greater importance was attached; they are introduced chiefly in out-of-the-way corners of the building, and in the substructures of great monumental combinations. This method of construction, being confined within such narrow limits, never resulted in Egypt in an architectural system;[105] neither did it give birth to any of those accessory forms which spring from its use.

Egyptian vaults may be divided into two great categories, according to the method of their construction.

1. Off-set vaults. These vaults are composed of courses off-set one from another, and with their faces hollowed to the segment of a circle. (Fig. 74.)

Fig. 74.—Element of

an off-set arch.

Fig. 75.—Arrangement of the courses

in an off-set arch.

If the face of those stones which, in the form of inverted steps, are turned to the void which has to be covered, be cut into the line of a continuous curve, the superficial appearance of a segmental arch or barrel vault will be obtained; but this appearance will be no more than superficial, the vault will be in fact a false one, because, in such a construction, all the stones which enframe the void and offer to the eye the form of a vault, are really laid horizontally one upon another, and their lateral joints are vertical. (Fig. 76.) When the units of such vaults are properly proportioned they are stable in themselves, and they have no lateral thrust.

Fig. 76.—Off-set semicircular arch.

2. Centred vaults. These are true vaults. They are composed of voussoirs, whose lateral joints are oblique, and radiate towards one centre or more. (Figs. 77, 78, and 79.)

Fig. 77.—Voussoir.

Fig. 78.—Arrangement of voussoirs.

This method of construction is very convenient because it enables the builder to utilize constructive units of very small dimensions, such as bricks. But this advantage has a corresponding drawback. These voussoirs thrust one against another and tend towards disintegration. They are not stable in themselves, and in order to give them stability they must be kept in place by surrounding them with opposing forces which will effectually prevent their setting up any movement in the structure of which they form a part. This function is fulfilled by the wall in Egyptian architecture, which is consequently very thick, but the radiating arch never arrived at such a development in Egypt as to lead to the adoption of any contrivance specially charged with the maintenance of vaults in a state of proper rigidity. The Egyptians not only employed the semicircular arch; they made use, in a few instances, of the pointed form, and many of their underground buildings have roofs cut out of the rock in the form of a segmental vault. The fact that these sepulchral chambers affected the aspect of vaulted halls, can only be explained by the supposition that a similar construction was common in the dwellings of the living.[106]

Fig. 79.—Semicircular vault.