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.
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.
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; 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.
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.
The Roman arch and Roman dome are always constructed ([Woodcut No. 110]) 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.
| 110. Radiating Arch. | 111. Horizontal Arch. |
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. 111]). From the time of the building of the Treasury of Mycenæ[252] 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,[253] near Halicarnassus,[254] where the dome exhibits all the peculiarities of construction found in the Jaina temples of India. After this we lose the thread of its history till the form reappears in porches like those of the 11th century on Mount Abu, 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.