History of Indian and Eastern Architecture v1.c19.s2: Domes.
History of Indian and Eastern Architecture v1.c19.s2
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- English
Domes.
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It is to be regretted that, while so much has been written on the history of the pointed arch, so little should have been said regarding the history of domes: the one being a mere constructive peculiarity that might very well have been dispensed with; the other being the noblest feature in the styles in which it prevails, and perhaps the most important acquisition with which science has enriched the art of architecture.
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The so-called Treasuries of Mycenæ and Orchomenos, as well as the chambers in Etruscan tombs, prove that as early as ten or twelve centuries before Christ the Pelasgic races had learned the art of roofing circular chambers with stone vaults, not constructed, as we construct them, with radiating vaults, on the principle of the common arch, but by successive layers of stones converging to a point, and closed by one large stone at the apex.
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Whoever invented the true or radiating arch, the Romans were the first who applied it as a regular and essential architectural feature, and who at the same time introduced its complement, the radiating dome, into architectural construction;
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at what period it is not now known. The earliest example, the Pantheon, is also the finest and largest; but we have lost entirely the innumerable steps by which the architects must have slowly progressed to so daring an experiment.
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There is, however, a vast difference between these two classes of domes, which it is necessary to bear in mind in order to understand what follows.
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The Roman arch and Roman dome are always constructed (Woodcut No. 170) on the principle of voussoirs, or truncated wedges, radiating from a centre. This enabled the Romans to cover much larger spaces with their domes than perhaps was possible on the horizontal principle; but it involved the inconvenience of great lateral thrusts, continually tending to split the dome and tear the building in pieces, and requiring immense and massive abutments to counteract their destructive energy.
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170. Radiating Arch.
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171. Horizontal Arch.
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The Indian or horizontal dome never can be made circular in section, except when used on the smallest scale, but almost always takes a form more or less pointed (Woodcut No. 171). From the time of the building of the Treasury of Mycenæ¹ to the birth of Christ, we have a tolerably complete series of arches and vaults constructed on this principle, but few domes properly so called. After the Christian Era the first example is found in a singular tomb at Mylassa,² near Halicarnassus in Caria,³ where the dome exhibits all the peculiarities of construction found in the Jaina temples of India. After this we almost lose the thread of its history till the form reappears in porches like those of the 11th century on Mount Âbû, where it is a perfectly established architectural feature, that must have been practised long before it could be used as we find it in that building. Whether we shall ever be able to recover the lost links in this chain is more than doubtful, but it would be deeply interesting to the history of art if it could be done. In the meantime, there is no difficulty in explaining the constructive steps by which the object is now attained in India. These may also throw some light on the history of the invention, though this is not, of course, capable of direct proof.
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¹ ‘History of Ancient and Mediæval Architecture,’ vol. i. p. 243.
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² *Ibid.* p. 371; and *ante*, p. 209.
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³ Fully illustrated in vol. ii. of the Dilettanti Society’s ‘Antiquities of Ionia.’
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The simplest mode of roofing a small square space supported by four pillars is merely to run an architrave or stone beam from each pillar, and cover the intermediate opening by a plain stone slab. Unless, however, slabs of great dimensions are available, this mode of construction has a limit very soon arrived at. The next step therefore is to reduce the extent of the central space to be covered by cutting off its corners; this is done by
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172. Diagram of Roofing.
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triangular stones placed in each angle of the square, as in Woodcut No. 172, thus employing five stones instead of one. By this means, the size of the central stone remaining the same, the side of the square space so roofed is increased in the ratio of ten to seven, the actual area being doubled. The next step in the process (Woodcut No. 173) is by employing three tiers and nine stones, instead of two tiers and five stones, which quadruples the area roofed. Thus, if the central stone is 4 ft., by the second process the space roofed will be about 5 ft. 8 in.; by the third 8 ft. square; by a fourth process (Woodcut No. 174)—with four tiers and thirteen stones
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173. Diagrams of Roofing. 174.
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—the extent roofed may be 9 ft. or 10 ft., always assuming the central stone to remain 4 ft. square. All these forms are still currently used in India, but with four pillars the process is seldom carried further than this; with another tier, however, and eight pillars (as shown in Woodcut No. 175), it may be carried a step further—exactly the extent to which it is carried in the tomb at Mylassa above referred to. In this, however, as in all instances of octagonal domes in this style, instead of the octagonal form being left as such, there are always four external pillars at the angles, so that the square shape is retained, with twelve pillars, of which the eight internal pillars may be taken as mere insertions to support the long architrave between the four angular pillars.
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175. Diagram of Roofing.
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It is evident that here again we come to a limit beyond which we cannot progress without using large and long stones. This was sometimes met by cutting off the angles of the octagon, and making the lower course of sixteen sides. When this has been done an awkwardness arises in getting back to the square form. This was escaped from, in all the instances I am acquainted with, by adopting circular courses for all above that with sixteen sides. In many instances the lower course with sixteen sides is altogether omitted, and the circles placed immediately
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[Figure: 176. Diagram of Indian Construction. B. Form of bracket capital in the angle of an octagonal dome.]
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on the octagon, as in the temple of Vimala at Âbû (Woodcut No. 284, vol. ii. p. 39). It is difficult to say how far this system might be carried constructively without danger of weakness. The Indian domes seldom exceed 30 ft. in diameter, but this may have arisen more from the difficulty of getting architraves above 12 ft. or 13 ft. in length to support the sides, than from any inability to construct domes of larger diameter in themselves. This last difficulty was to some extent got over by a system of bracketing, by which more than half the bearing of the architrave was thrown on the capital of the column, as shown in Woodcut No. 176. Of course this method might have been carried to any extent, so that a very short architrave would suffice for a large dome; but whether this could be done with elegance is another matter. The Indians seem to have thought not; at least, as far so I know, they never carried it to any extent. Instead of bracketing, however, they sometimes used struts, as shown in Woodcut No. 176, but it is questionable whether that could ever be made a really serviceable constructive expedient in stone architecture.
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The great advantage to be derived from the mode of constructing domes just described was the power it gave of placing them on pillars without having anything to fear from the lateral thrust of the vault. The Romans never even attempted this, but always, so to speak, brought their vaults down to the ground, or at least could only erect them on great cylinders, which confined the space on every side. The Byzantine architects cut away a great deal of the substructure, but nevertheless could never get rid of the great heavy piers they were forced to employ to support their domes; and in all ages were forced to use either heavy abutments externally, or to crowd their interiors with masses of masonry, so as in a great measure to sacrifice either the external effect or the internal convenience of their buildings to the constructive exigencies of their domes. This in India never was the case; all the pressure was vertical, and to ensure stability it only required sufficient strength in the support to bear the downward pressure of the mass—an advantage the importance of which is not easily over-estimated.
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One of the consequences of this mode of construction was, that all the decoration of the Indian domes was horizontal, or, in other words, the ornaments were ranged in concentric rings, one above the other, instead of being disposed in vertical ribs, as in Roman or Gothic vaults.¹ This arrangement allows of far more variety without any offence to good taste, and practically has rendered some of the Indian domes the most exquisite specimens of elaborate roofing that can anywhere be seen. Another consequence of this mode of construction was the employment of pendants from the centres of the domes, which are used to an extent that would have surprised even the Tudor architects of our own country. With them, however, the pendant was an architectural *tour de force*, requiring great constructive ingenuity and large masses to counterbalance it, and is always tending to destroy the building it ornaments; while the Indian pendant, on the contrary, only adds its own weight to that of the dome, and has no other prejudicial tendency. Its forms, too, generally have a lightness and elegance never even imagined in Gothic art; it hangs from the centre of a dome more like a lustre of crystal drops than a solid mass of marble or of stone.
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¹ The tendency of the Indian construction, however, was to make the section of the dome nearly conical as each course or ring of stone, after the first two or three, had about the same amount of projection inwards.
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As before remarked, the eight pillars that support the dome are almost never left by themselves, the base being made square by the addition of four others at the angles. There are many small buildings so constructed with only twelve pillars, as shown in the annexed diagram (No. 177), but two more are oftener added on each face, making twenty altogether, as shown on the upper side of the annexed diagram (No 178); or four on each face, making twenty-eight; or again, two in front of these four, or six on each face, so as to make thirty-six; and the same system of aggregation is carried on till the number of pillars reaches fifty-six (Woodcut No. 179), which is the largest number I ever saw surrounding one dome; but any number of these domes may surround one temple, or central dome, and the number consequently be multiplied almost *ad infinitum*. When so great a number of pillars is introduced as in the last instance, it is usual to make the outmost compartment on each face square, and surmount it with a smaller dome. This is occasionally though rarely done even with the smallest number.
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[Figure: 177. Diagram of the arrangement of the pillars of a Jaina Dome.]
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[Figure: 178. Diagram Plan of Jaina Porch.]
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The first result of this arrangement is, that the Hindûs obtained singularly varied outline in plan, producing the happiest effects of light and shade with every change in the sun's position. Another result was, that by the accentuation of the salient and re-entering angles, they produced those stronglymarked vertical lines which give such an appearance of height to Gothic designs. To accomplish this, however, the Western architects were obliged to employ buttresses, pinnacles, and other constructive expedients. The Hindûs obtained it by a new disposition of the plan without anywhere interrupting the composition. This form of outline also expresses the internal arrangements of the porch better than could be done by the simpler outline of either a square or circle, such as is usually employed in Europe. Its greatest merit, however, is, that the length of the greater aisles is exactly proportioned to their relative width as compared with that of the subordinate aisles. The entrance being in the angle, the great aisle forms the diagonal, and is consequently in the ratio of 10 to 7, as compared to what it would be if the entrance were in the centre of the side, where we usually place it. From the introduction of the octagonal dome in the centre the same proportion (correctly 1000 to 707) prevails between the central and side aisles, and this again is perhaps the most pleasing that has yet been introduced anywhere. In Gothic churches the principal aisles are generally twice as wide as the side ones, but they are also twice as high, which restores the proportion. Here, where the height of all is the same, or, nearly so, this gradation just suffices to give variety, and to mark the relative importance of the parts, without the one overpowering the other: and neither has the appearance of being too broad nor too narrow.
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179. Diagram of Jaina Porch.
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It is, of course, difficult for those who have never seen a building of the class just described to judge of the effect of these arrangements; and they have seldom been practised in Europe. There is, however, one building in which they have accidentally been employed to a considerable extent, and which owes its whole beauty to the manner in which it follows the arrangement above described. That building is Sir Christopher Wren's church of St. Stephens, Walbrook. Internally its principal feature is a dome supported on eight pillars, with four more in the angles, and two principal aisles crossing the building at right angles, with smaller square compartments on each side. This church is the great architect's masterpiece, but it would have been greatly improved had its resemblance to a Hindû porch been more complete. The necessity of confining the dome and aisles within four walls greatly injures the effect as compared with the Indian examples. Even the Indian plan of roofing, explained above, might be used in such a building with much less expense and less constructive danger than a Gothic vault of the same extent.