ARCH. A structure composed of separate inelastic bodies, arranged in such a manner that their lower surface shall form the arc of a curve, being supported at its two extremities.
History. The invention of the arch has been assigned by different writers respectively to Babylonians, Egyptians, Greeks, Romans, and Etruriens.
The claim made for the Babylonians rests principally on a passage found in Strabo, wherein he states, that the Hang ing-Gardens were formed by means of arches : a passage of Herodotus is also quoted, as favouring the supposition. This historian, speaking of the great gates in the eity-wall, relates, that Nitoeris was buried in a chamber above one of them, and it is urged by the supporters of this opinion, that so heavy a superstructure could not have been supported over an aperture of such dimensions by mere beams, or indeed by any other contrivance than that of the arch. On the other side it is argued, that Nitocris would have made use of the arch in the erection of her bridge, had the prin ciples of its construction been understood, instead of the awkward application of horizontal timber beams ; and with respect to the gateways, it is stated, that Herodotus, in this instance, speaks of jambs and lintels, and makes not the slightest mention of an arch. Besides, it is argued, if the arch was used to any extent, we should certainly find some vestiges of it in the ruins of that city, whereas the concurrent testimony of all travellers goes to prove that none such exist, while liinelling has been found in several instances, where the arch might have been applied with advantage.
In favour of the Egyptian title to this distinction, we are referred to specimens of arched work still to be found in the remains of Egyptian temples. The first specimen pro duced is from Abydos, where the roof is certainly of an arched form, but on inspection proves to be constructed of three horizontal stones; the centre one, which is the largest., overlapping the two side-ones. The under surface of these stones is cut out in such a manner as to form a semicircular arch. The other specimens adduced, are without doubt true arches, and if their antiquity be allowed, the question is at once set at rest. These arches are found at Thebes, and are formed of flfr courses of bricks arranged in a semicircle. If the fact of their antiquity, however, be admitted, it is difficult to understand why the arch should not have been more generally employed.
The same reasoning may he applied in the ease of the Greeks, for, although it. is said that true arches are found
in their works, yet it seems probable that they were not in use previous to the second or third century before the Christian era, as, if so, we should naturally expect to find them employed in many cases where they would have proved most useful. The general arrangement of their buildings would scarcely have been such as it is, it' they had been acquainted with the principles of the art.
The first example of any arched construction to be found among the Romans, is that of the cloaca maxima, or public sewer, said to have been built by Tarquin. The identity of the existing remains with the original structure has been doubted, but in fact this is of no great importance, as there is no scarcity of examples of this kind, although of somewhat later date than the reign of Tarquin. There are some who assign the met; of the introduction of the arch among the Romans to the Etrusci, and who are not entirely without reasons for this assumption. They say that Tarquin brought this knowledge with him from Etruria, his native country, and that Etrurians were employed by him in the construc tion of the sewer ; others, however, refer the actual con struction to Greeks. It is possible indeed that the Etrurians may have introduced this form of building, as it is well known that that people had arrived at some excellence in the arts at an early period, and also were in close commu nication with the Romails ; be this, however, as it may, there can be no doubt that we are principally indebted to the latter people for the full development of the power and utility of the arch ; whoever it may have been who first became acquainted with the principles, whether Egyptians, Greeks, Romans, or Etrurians, there never was any doubt as to the people who carried its knowledge into execution. As far as the Greeks or their predecessors are concerned, we might have remained in utter ignorance as to the utility of this style of building. It is to the Romans we owe our practical knowledge on the subject ; they it was who made a worthy application of their knowledge, and put their theories into extensive execution ; and although they em ployed this form to a greater extent than perhaps good taste might sanction ; yet this we judge to be the natural pro cedure of any people upon first becoming acquainted with a principle of so peculiar a character and such unlimited usefulness.