A History of Art in Chaldaea & Assyria Part 18

In the preceding pages we have determined the _role_ played by the column in a.s.syria, and have explained that in spite of the care and taste lavished upon some of its details, it never rose above the rank of a secondary and subordinate member. There is nothing, then, to surprise us in the fact that the a.s.syrian architect never placed his arches or vaults upon columns or piers; he seems never to have had a glimpse of the great possibilities such a procedure involved, a procedure from which upon the very soil of the East, his remote descendants were to evolve the architecture of the Byzantine church and the Arab mosque. His archivolts and the pendentives of his vaults always rest upon thick walls, and yet almost every variety of the simple arch or tunnel-vault are to be found among the ruins of his buildings.

[Ill.u.s.tration: FIG. 89.--Tomb-chamber at Mugheir; from Taylor.]

Like all the other forms of a.s.syrian architecture the arch was invented in Chaldaea. The use of small sized materials must have led to its early discovery in that country. But the only arches now standing occur in the better preserved monuments of a.s.syria. On the other hand the tombs of Lower Chaldaea furnish more than one example of that false, corbelled or off-set vault, that we have already encountered in Egypt.[280] The chamber figured below is taken from the necropolis of Mugheir, formerly "Ur of the Chaldees." It is built of crude brick bound with mud. The vault is supported by walls sloping upwards and outwards like those of a modern tunnel (Fig. 89).[281]

Such a method of construction is only adapted to buildings of small dimensions; it could not be used for chambers with wide roofs, or where any great weight was to be upheld. The arches upon which, according to both Strabo and Diodorus,[282] the hanging gardens of Babylon were supported, must have been real centred arches. As to whether they were of pise, like those of Khorsabad, the Greek writers tell us nothing. From what we know of the habits of the Chaldaean builder we may conclude that they were true arches with voussoirs either of bricks burnt in the kiln, or so well dried that they were almost as hard and durable as those that had pa.s.sed through the fire. This conjecture is confirmed by the fact that the structures in question lasted till the Macedonian conquest. Strabo and Diodorus speak of the great temple of Bel as so ruinous that its original height could not be guessed, even approximatively. It was otherwise with the hanging gardens.

Of these they give the measurements, on plan, of the platforms and piers, together with their heights, and the heights of the arches. We should find it difficult to explain the preciseness of these measurements and their agreement one with another, unless we supposed that both writers had some exact authority, such as one of the companions or historians of Alexander, to refer to. The kings of Persia lived at Babylon for a part of the year.

These princes may well have been indifferent to the preservation of the national fanes, they may even have hastened their destruction, as Xerxes is said to have done, in order to punish and humiliate the rebellious Babylonians. But in their own interest they would see that proper care was taken of those hanging gardens by which their stay in the city would be rendered more pleasant than it would otherwise have been, from whose lofty platforms their watchful eyes could roam over the city and the adjoining plain, and follow the course of the great river until it disappeared on the south amid groves of waving palm. After the rise of Seleucia and Ctesiphon, however, the gardens would rapidly hasten to decay, but they must have been solidly built in the first instance to last as long as they did. The pise vaults of the Ninevite palaces could never have stood so well. In spite of the layers of lead and bitumen which, as Diodorus tells us, were spread upon their terraces, the summer rains must in time have found their way into their walls and set up a process of disintegration which could have but one end. Real brick with good mortar could alone resist such influences, and those, no doubt, were the materials used in the Babylonian gardens. If their substructures should ever be found and laid open, we have little doubt that arches as carefully built as those of the a.s.syrian ruins will be brought to light.

The gateways of the town built by Sargon at the foot of his palace mound were roofed with semicircular vaults.[283] In order to study their construction more closely, M. Place demolished one of these arches piece by piece, the one numbered three on his plan.[284] It was already condemned to destruction by the necessity for carrying off its sculptures.

The total height from pavement to keystone, was twenty-four feet six inches, from the centre of the keystone to the springing of the arch itself was eight feet, the total width of the opening, measured at the feet of the caryatides, was fourteen feet four inches.

The bricks had not been burnt in a kiln but they had been subjected to a prolonged desiccation. The system of construction was as simple as possible. The perpendicular side walls pa.s.sed into the vault without any preparation, and the arch when complete had no inward projection and no structural ornament but the inner faces of the carefully placed voussoirs; as all the bricks were of the same size and shape something more than their slightly trapezoidal form was required to keep them in place, and a softer clay was used to bind them together. With the addition of this rude cement each brick became a long and narrow wedge and determined the curve of the vault in which it was placed. Some idea of the appearance of this triple arch may be formed from the ill.u.s.tration we have compiled from M. Thomas's elevation of an alcove in one of the harem apartments at Khorsabad (Fig.

90). This vault is not in existence, but its component parts were found among the ruins of Sargon's palace.[285]

[Ill.u.s.tration: FIG. 90.--Interior of a chamber in the harem of Sargon's palace at Khorsabad; compiled from Place.]

There is one detail in the decoration of these doorways that should be carefully noted. Wherever the architect makes use of a round-headed opening he reinforces its outlines with a kind of semicircular frieze, to which brilliant colours or bold reliefs would give no little decorative value.

In what M. Place calls _portes ornees_, this ornamental archivolt is of enamelled bricks, in the subordinate entrances it is distinguished from the rest of the wall merely by its salience. In neither case, however, does it end in any kind of impost, it returns horizontally without the arch and forms an ornament along a line corresponding to the spring of the vault within. We give an example of this peculiarly a.s.syrian arrangement from one of the gateways at Dour-Saryoukin (Fig. 91). Nothing like it is to be found, so far as we know, among the buildings of any other ancient people.

[Ill.u.s.tration: FIG. 91.--Return round the angle of an archivolt in one of the gates of Dour-Saryoukin; compiled from Place.]

From the point of view of the special study on which we are now busy, the inhabited and visible part of an a.s.syrian building is less interesting than those channels hidden in the substructures which acted as drains. These channels existed in all the palaces. Layard encountered them at Nimroud and Kouyundjik,[286] but it was at Khorsabad that they were found in the best condition and most carefully studied.[287] We shall make use chiefly of the observations of MM. Place and Thomas in our explanation of a curious system of sewers that does, perhaps, more honour to the Ninevite builder than any other part of his work. Every detail of their construction is full of interest,--the general arrangement, the choice of materials and the various methods of vaulting brought into play.

In nearly all the rooms there is an opening in the middle of the pavement towards which the rest of the floor has a gentle slope. It is a round hole cut through the centre of a square stone set among the bricks and leading to a circular brick conduit. In the first specimen described by M. Place, this descending pipe is five feet four inches deep, and rather more than eleven inches in diameter. It leads into an almost horizontal conduit with a similar section and of the same materials. This latter channel is gently inclined through the whole of its length; it terminates in the main drain of which the cut on the next page gives a section in perspective (Fig.

92).[288]

The floor of this sewer was formed of large limestone slabs overpa.s.sing the inside width of the channel by several inches. By this means the internal joints were reduced to a minimum, and a further precaution was taken by placing the slabs in a bath of asphalte, which was also used to coat the oblique channels and the foot of the vertical pipe. The low perpendicular walls upon which the vault was to be placed were built upon the outer edge of these wide slabs. They were of four-inch bricks, carefully laid.

The most remarkable thing about this drain is the construction of the vault. The bricks composing it are trapezoidal in shape, two of their edges being slightly rounded, the one concave, the other convex. The radius of this curve varies with each brick, being governed by its destined place in the vault. These bricks go therefore in pairs, and as there are four courses of bricks on each side of the vault, four separate and different moulds would be required, besides a fifth, for a brick of which we shall presently have to speak. The four narrow sides of these bricks differ sensibly one from another. The two curved faces being at different distances from the centre, are of unequal lengths, while, as the lower oblique edge is some inches below the upper in the curve, these two edges have different directions. In their disinclination to use stone voussoirs, the a.s.syrian builders here found themselves compelled to mould bricks of very complicated form, and the way in which they accomplished their task speaks volumes for their skill.

[Ill.u.s.tration: FIG. 92.--Drain at Khorsabad, with pointed arch. Section in perspective.]

If we cast a glance at our Fig. 92 the first thing that strikes us is the absence of a keystone to the vault. The two rows of voussoirs that are in full view thrust against each other only by a single sharp edge; there is no keystone between them. In the row immediately behind, however, there is a stone (imperfectly seen in our ill.u.s.tration) that seems to play the part of a key. Thus we find that only at each alternate vertical course was the arch of burnt and moulded brick complete. The openings left at the summits of the other courses must have been filled in in some way, and, in fact, the line of voids which ran along the top of the extrados was filled in with brick earth, beaten tight and forming the best of keys. So that the vault was completed and consolidated by the same material as that used to make its channel impervious to water.[289]

This vault has another strange singularity which at first is very surprising. The whole structure has a sensible inclination in the direction of its length, suggesting that some accident had happened to it in course of erection. Such an explanation must be rejected, however, because at the moment of discovery the whole arrangement was uninjured, and, moreover, the filling of clay must have rendered any movement of the kind impossible. M.

Place's explanation seems the best. He thinks the slope was given merely to facilitate the work of the bricklayers. The first course of voussoirs would be sloped in this fashion, and would rest upon some ma.s.s of crude brick in the centre of the building. The bricks of the second course would lean against it, and their weight would be brought in to add cohesion and solidity to the whole structure instead of being entirely occupied in adding to the perpendicular thrust, while the ease with which they could be placed without an internal support would be much increased. a.s.sisted by this simple expedient, two bricklayers with their labourers could build the vault at a very rapid rate. We may believe that the notion of building in this way would never have occurred to the a.s.syrian architects but for their habit of dispensing with timber centres.

This slope had an effect upon the arrangement of the bricks which should be noticed. In all other vaults, such as those of the city gates, the units are laid upon their longest sides, and a vertical section shows their shortest diameters. Here, on the other hand, the bricks stand on their edges, and their largest surfaces are in contact, on each side, with the next vertical course. If the full benefit of the natural cohesion between one brick and another was to be obtained, this method of laying them was absolutely necessary.

Internally, the drain we have been studying was four feet eight inches high from the floor to the crown of the vault. Its width was three feet nine inches, and its general slope very slight. It may be followed for a total length of about 220 feet, after which falls of earth have carried away the arch and the whole northern part of the esplanade, so that no trace of the mouth by which it opened on the plain can be traced.

The other sewer described by M. Place may be more summarily dismissed. In spite of their drawings and minute descriptions, explorers have not yet succeeded in explaining the eccentricities of construction it presents. It has two channels, one above the other, which are similar neither in slope nor section. Moreover this double sewer is abruptly interrupted in the middle of the artificial mound through which it runs. Must we believe that it was never finished or used? We shall not attempt to answer this question, but shall content ourselves with pointing to the similarities between this tunnel and the last described. The same large stone slabs upon a layer of bitumen, the same inclination of the body of the vault, the same bricks formed in different moulds according to their place in the vault, are found in each.

Our Fig. 93 shows the two channels and their position one above the other.

The pavement of the terrace, which consists of a double bed of large bricks, rests upon the extrados of the upper channel. This vault is semicircular; it has three voussoirs on each side, which, with the key, make seven in each vertical course. But in consequence either of an error in measurement or of a mistake in calculating the shrinking of the bricks, there was a gap between the third voussoir on the right and the key. This gap was filled in by the insertion of a stone cut into the shape of a wedge. But for this fault--which, however, had no appreciable effect upon its solidity--the vault would be perfect.[290] The narrow triangular opening of the lower channel may be seen below it.

The semicircular vault gradually and insensibly changes into an elliptical one. The side walls become lower, at each yard their height is diminished by the thickness of a brick, and finally they disappear about the middle of the total length. At the point shown in our Fig. 94 the arch has lost its supports and rests directly upon the pavement of the channel. Its ellipse is composed of eight voussoirs, four on each side, and a key with a small wedge-shaped stone voussoir on each side of it. Between the two points shown in our Figs. 93 and 94 the upper and lower sewers have become one, the vaulted roof of the first and the paved floor of the second being continued in a single tunnel. At the point where this tunnel comes to a sudden end it is closed by a wall, through which two small openings are pierced to serve as outlets for the sewer within (Fig. 94).

[Ill.u.s.tration: FIG. 93.--Sewer at Khorsabad, with semicircular vault; compiled from Place.]

At different points on the Khorsabad mound, M. Place found other sewers, some with depressed, some with basket-handle vaults, while, at Nimroud, channels were discovered which were square in section and covered with large slabs of limestone.[291] The a.s.syrian architects seem, however, to have had a decided preference for the vault in such a situation. They expected it to give greater solidity, and in that they were not mistaken.

The vaults of burnt brick, though set without cement, have remained unshaken and close in their joints, and the sewers they inclose are the only voids that have remained clear in the ruins of the buildings to which they belong.

[Ill.u.s.tration: FIG. 94.--Sewer at Khorsabad, with elliptical vault; compiled from Place.]

We may, perhaps, be accused of dwelling too minutely upon these a.s.syrian vaults. We have done so because there is no question more interesting or more novel in the whole history of architecture than the true origin of the keyed vault and the different uses to which it has been put. Ottfried Muller looked upon the Etruscans as the inventors of the vault; he believed that the Greek builders learnt the secret from the early inhabitants of Italy,[292] and that the arches of the Roman _Cloaca Maxima_ built by the Tuscan architects of the Tarquins, were the oldest that had come down to us from antiquity. The archaeological discoveries of the last fifty years have singularly falsified his opinion and given an age to the vault never before suspected. Even in the days of the Ancient Empire the Egyptians seem to have understood its principle; in any case the architects of Amenophis, of Thothmes, of Rameses, made frequent and skilful use of it long before the Ninevite palaces in which we have found it were erected.[293] But the possession of stones of enormous size enabled the Egyptians to dispense to a great extent with the arch, and we need not be surprised, therefore, that they failed to give it anything like its full development. They kept it in the background, and while using it when necessary in their tombs, in the outbuildings of their temples, in their private dwellings and warehouses, they never made it a conspicuous element of their architectural system.

They may well be admired for the majesty of their colonnades and the magnificence of their hypostyle halls, but not for the construction of their vaults, for the imitation of which, moreover, they gave little opportunity.

In Chaldaea and a.s.syria the conditions were different. Supposing the architecture of those two countries to be yet entire, should we find in it vaults rivalling in age the arch in a tomb at Abydos which Mariette attributes to the sixth dynasty?[294] Probably not. So far as we can judge, Chaldaean civilization does not date from so remote a past as that of Egypt, but it appears certain that the principles of the vault were discovered and put in practice by the Chaldees long before the comparatively modern times in which the segmental and pointed arches of Nineveh were erected. The latter alone are preserved because they have been hidden during all these centuries under the heaped-up ruins of the buildings to which they belonged, while those of Chaldaea have been carried away piece by piece, and their materials used again and again by the modern population of Mesopotamia.

In spite, however, of the absence of such direct evidence, we may affirm without fear that the Chaldaean architects soon discovered the principle of the arch, and used it at least in its simplest and least complex forms. We are led to these conclusions not only by their restriction to small units of construction--a restriction which is sure, sooner or later, to lead to the discovery in question--but also by induction from the monuments we have just been studying. The arches under the hanging gardens of Babylon, the vaults of the sewers and gateways, the domes that covered the great square chambers in the Ninevite palaces--all these were derived, we may be sure, from the ancient civilization. We cannot believe that such consummate skill in the management of a difficult matter was arrived at in a day. The purely empiric knowledge of statics it implies could only have been acc.u.mulated by a long series of more or less happy experiments.

Thus only can we explain the ease with which the a.s.syrian builder surmounted difficulties some of which would have puzzled a modern architect, such as the pise vaults erected over s.p.a.cious galleries without any kind of centering, and the domes over square chambers, for which some system of pendentives--that is, of arches or other intermediate forces--by which the base of the cupola could be allied to the top of the supporting wall, must have been contrived. The accurate calculation of forces between the thrust of the vaults and the strength of the retaining walls, the dexterity with which the curves employed are varied and carried insensibly one into the other, the skill with which the artificial materials are prepared for their appointed office, are also surprising. By careful moulding and manipulation the a.s.syrian builder made his brick voussoirs as well fitted for their work as the cut stone of our day. Each brick had its own shape and size, so that it was a.s.signed in advance a particular place in the vault and its own part in a.s.suring the final stability of the building. In all this we cannot avoid seeing the results of a patient and long-continued process of experiment and education carried on through many centuries in all the workshops of Mesopotamia.

The art of building vaults with small units of construction was, then, carried farther in Mesopotamia than in Egypt; it was there more frankly developed; it was there forced with greater success to supply the place of stone and timber. It was in fact more of an indigenous art in the valley of the Tigris and Euphrates than anywhere else, more inspired by the permanent and unchanging conditions of the country--in a word, more national.

In these days the historian sets himself with devotion to follow in all its involutions the long chain of thought and effort by which man has been led from his primitive barbarism to the well-being of modern civilization, and to his domination--every day more complete and more intelligent--over the minor forces of nature. It is the duty of criticism, as its methods gradually perfect themselves, to add daily to its perspicacity and powers of observation, and to lessen as much as possible the occasions, still so numerous, when the thread of evidence breaks in its hands and the true relations of facts to each other become obscured. Even yet we cannot say for certain to which nation of the ancient world the invention of the arch belongs. In those remote ages the principle may have been discovered more than once or twice in different and distant countries whose inhabitants were busied over the same task. We have no reason to believe that Chaldaea learnt the secret from Egypt, or Etruria from the East. It is none the less true, however, that the unknown architects of Babylon and Nineveh made full use of it at an earlier date and in more intelligent fashion than any of their rivals. To them must be given the credit of being the masters and art-ancestors of the men who built the Pantheon and the Church of Saint Sophia, Santa Maria del Fiore, and Saint Peter's in Rome, and more especially of those great modern engineers to whom the principle of the arch has been a chief element in their success.

NOTES:

[280] _Art in Ancient Egypt_, vol. ii. p. 82.

[281] This chamber is 7 feet long, 3 feet 7 inches wide, and 5 feet high.

TAYLOR, _Journal of the Royal Asiatic Society_, vol. xv. p. 272.

[282] STRABO, xvi. 1, 5. DIODORUS, ii. 10.

[283] PLACE, _Ninive_, vol. i. pp. 170-182 and 256-259, vol. iii. plates 9-18.

[284] PLACE, _Ninive_, vol. iii. plate 2.

[285] PLACE, _Ninive_, vol. i. p. 128.

[286] LAYARD, _Nineveh_, vol. i. p. 134; vol. ii. pp. 79 and 261.

_Discoveries_, pp. 162-165.

[287] PLACE, _Ninive_, vol. i. pp. 269-280 and plates 38 and 39.

[288] We have endeavoured to combine M. Thomas's longitudinal elevation, vertical section, and transverse section (PLACE, _Ninive_, plate 38), in our single cut.

[289] The same process was employed at Nimroud in a drain or water channel, of which LAYARD gives a sketch (_Discoveries_, p. 164). In connection with these vaults we must remember that a pointed arch has no key properly speaking; the top stone is merely a joint. It looks as if the a.s.syrian architect had a kind of instinctive appreciation of the fact.

[290] The slope, the height, and the width of this channel are not the same throughout. In some places it is wide enough to allow two men to walk abreast in it.