CHAPTER V

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INVENTION OF THE ARCH.

Before leaving this early section of architecture, it may be as well briefly to refer to the invention of the true arch, regarding which considerable misconception still exists.

It is generally supposed that the Egyptians were ignorant of the true principles of the arch, and only employed two stones meeting one another at a certain angle in the centre when they wished to cover a larger space than could conveniently be done by a single block. This, however, seems to be a mistake, as many of the tombs and chambers around the pyramids and the temples at Thebes are roofed by stone and brick arches of a semicircular form, and perfect in every respect as far as the principles of the arch are concerned.

Several of these have been drawn by Lepsius, and are engraved in his work; but, as no text accompanies them, and the drawings are not on a sufficient scale to make out the hieroglyphics, where any exist, their date cannot now be ascertained. Consequently, these examples cannot yet be used as the foundation of any argument on the subject, though the curved form of the roofs in the Third Pyramid would alone be sufficient to render it more than probable that during the period of the 4th dynasty the Egyptians were familiar with this expedient.[99]

At Beni-Hasan, during the time of the 12th dynasty, curvilinear forms reappear in the roofs (Woodcut No. 16), used in such a manner as to render it almost certain that they are copied from roofs of arcuate construction. Behind the Rameseum at Thebes there are a series of arches in brick, which seem undoubtedly to belong to the same age as the building itself; and Sir G. Wilkinson mentions a tomb at Thebes, the roof of which is vaulted with bricks, and still bears the name of Amenoph I., of the 18th dynasty.[100]

The temple at Abydus, erected by Rameses II., shows the same peculiarity as the tombs at Beni-Hasan, of a flat segmental arch thrown across between the stone architraves. In this instance it is also a copy in stone, but such as must have been originally copied from one of brick construction. There is also every reason to believe that the apartments of the little pavilion at Medeenet Habû (Woodcuts Nos. 32 and 33) were covered with semicircular vaults, though these have now disappeared.[101]

In Ethiopia Mr. Hoskins found stone arches vaulting the roofs of the porches to the pyramids, perfect in construction, and, what is still more singular, showing both circular and pointed forms (Woodcut No. 105). These, as before remarked, are probably of the time of Tirhakah, or at all events not earlier than the age of Solomon, nor later than that of Cambyses.

[Illustration: 101. Section of Tomb near the Pyramids of Gizeh.]

In the age of Psammeticus we have several stone arches in the neighbourhood of the pyramids; one, in a tomb at Sakkara, has been frequently drawn; but one of the most instructive is that in a tomb discovered by Colonel Campbell (Woodcut No. 101), showing a very primitive form of an arch composed of 3 stones only, and above which is another arch of regular construction of 4 courses. In his researches at Nimroud, Layard discovered vaulted drains and chambers below the north-west and south-east edifices, which were consequently as old as the 8th or 9th century before our era, and contemporary with those in the pyramids of Meroë. They were of both circular and pointed forms, and built apparently with great care and attention to the principles of the arch (Woodcut No. 102).

[Illustration: 102. Vaulted Drain beneath the South-East Palace at Nimroud.]

The great discovery of this class is that of the city gates at Khorsabad, which, as mentioned at p. 181, were spanned by arches of semicircular form, so perfect both in construction and in the mode in which they were ornamented, as to prove that in the time of Sargon the arch was a usual and well-understood building expedient, and one consequently which we may fairly assume to have been long in use.

[Illustration: 103. Arch at Dêr-el-Bahree. (Lepsius.)]

On the other hand, we have in the temple at Dêr-el-Bahree in Thebes, built by Thothmes III., a curious example of the retention of the old form, when at first sight it would appear as though the true arch would have been a more correct expedient. In this example, the lower arch is composed of stones bracketing forward horizontally, though the form of the arch is semicircular; and above this is a discharging arch of two stones used as in the Pyramids. The upper arch is so arranged as to relieve the crown of the lower—which is its weakest part—of all weight, and at the same time to throw the whole pressure on the outer ends of the arch stones, exactly where it is wanted. The whole thus becomes constructively perfect, though it is a more expensive way of attaining the end desired than by an arch.

The truth seems to be, the Egyptians had not at this age invented voussoirs deeper in the direction of the radii of the arch than in that of its perimeter; and the arch with them was consequently not generally an appropriate mode of roofing. It was the Romans with their tiles who first really understood the true employment of the arch.

So far as we can now understand from the discoveries that have been made, it seems that the Assyrians used the pointed arch for tunnels, aqueducts, and generally for underground work where they feared great superincumbent pressure on the apex, and the round arch above-ground where that was not to be dreaded; and in this they probably showed more science and discrimination than we do in such works.

[Illustration: 104. Arch of the Cloaca Maxima, Rome. Scale 50 ft. to 1 in.]

In Europe the oldest arch is probably that of Cloaca Maxima at Rome, constructed under the early kings. It is of stone in 3 rims, and shows as perfect a knowledge of the principle as any subsequent example. Its lasting uninjured to the present day proves how well the art was then understood, and, by inference, how long it must have been practised before reaching that degree of perfection.

From all this it becomes almost certain that the arch was used as early as the times of the pyramid-builders of the 4th dynasty, and was copied in the tombs of Beni-Hasan in the 12th; though it may be that the earliest existing example cannot be dated further back than the first kings of the 18th dynasty; from that time, however, there can be no doubt that it was currently used, not only in Egypt, but also in Ethiopia and Assyria.

It would, indeed, be more difficult to account for the fact of such perfect builders as the Egyptians being ignorant of the arch if such were the case; though, at the same time, it is easy to understand why they should use it so sparingly, as they did in their monumental erections.

Even in the simplest arch, that formed of only two stones, such as is frequently found in the pyramids, and over the highest chamber (Woodcut No. 8), it will be evident that any weight placed on the apex has a tendency to lower the summit, and press the lower ends of the stones outwards. Where there was the whole mass of the pyramid to abut against, this was of no consequence, but in a slighter building it would have thrust the walls apart, and brought on inevitable ruin.

The introduction of a third stone, as in the arch (Woodcut No. 101), hardly remedied this at all, the central stone acting like a wedge to thrust the two others apart; and even the introduction of 2 more stones, making 5, as in Woodcut No. 105, only distributed the pressure without remedying the defect; and without the most perfect masonry every additional joint was only an additional source of weakness.

[Illustration: 105. Arches in the Pyramids at Meroë. (From Hoskins.)]

This has been felt by the architects of all ages and in all countries: still, the advantage of being able to cover large spaces with small stones or bricks is so great, that many have been willing to run the risk; and all the ingenuity of the Gothic architects of the Middle Ages was applied to overcoming the difficulty. But even the best of their buildings are unstable from this cause, and require constant care and attention to keep them from falling.

The Indian architects have fallen into the other extreme, refusing to use the arch under any circumstances, and preferring the smallest dimensions and the most crowded interiors, to adopting what they consider so destructive an expedient. As mentioned in the Introduction (page 22), their theory is that “an arch never sleeps,” and is constantly tending to tear a building to pieces: and, where aided by earthquakes and the roots of trees, there is only too much truth in their belief.

The Egyptians seem to have followed a middle course, using arches either in tombs, where the rock formed an immovable abutment; or in pyramids and buildings, where the mass immensely overpowered the thrust; or underground, where the superincumbent earth prevented movement.

They seem also to have used flat segmental arches of brickwork between the rows of massive architraves which they placed on their pillars; and as all these abutted one another, like the arches of a bridge, except the external ones, which were sufficiently supported by the massive walls, the mode of construction was a sound one. This is exactly that which we have re-introduced during the last 30 years, in consequence of the application of cast-iron beams, between which flat segmental arches of brick are thrown, when we desire to introduce a more solid and fire-proof construction than is possible with wood only.

In their use of the arch, as in everything else, the building science of the Egyptians seems to have been governed by the soundest principles and the most perfect knowledge of what was judicious and expedient, and what should be avoided. Many of their smaller edifices have no doubt perished from the scarcity of wood forcing the builders to employ brick arches, but they wisely avoided the use of these in all their larger monuments— in all, in fact, which they wished should endure to the latest posterity.

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