THE

ECLECTIC REVIEW,

For JULY, 1809.

Art. I. A Treatise of the Properties of Arches and their Abutment Piers: containing Propositions for describing geometrically the Catenaria, and the Extradosses of all Curves, so that their several Parts and their Piers may equilibrate; also, concerning Bridges, and the Flying Buttresses of Cathedrals. To which are added, in Illustration, Sections of Trinity Church, Ely; King's College Chapel, Cambridge; Westminster Abbey; Salisbury, Ely, Lincoln, York, and Peterborough Cathedrals. By Samuel Ware, Architect. Royal 8vo. pp. xii. 62. 19 folding Plates. Price 10s. 6d. J. Taylor; Longman and Co. 1809. IT would be a very entertaining and instructive employment, for a man of leisure, with the requisite acquire ments, to trace the progress of arch-building and its gradual modifications, from its first rude origin to the present time. Arches are observed in the most ancient buildings of Greece, such as the temple of the Sun at Athens, and that of Apollo, at Didymas: but these arches were not intended as roofs to any apartment, or as part of the ornamental design; they were concealed in the walls, covering drains or other necessary openings; nor have we found any real arches, such, we mean, as were meant to be seen while they were constructed for purposes of utility, in any monuments of ancient Persia. No trace of an arch is to be seen in the ruins of ancient Egypt: there are, it is true, in the Pyramids, two galleries whose roofs consist of many pieces; but it is manifest from the construction that the builder had no notion of the nature of an arch; they can no more be called arched-vaultings, than many of the Egyptian wide rooms which are covered with a single block of stone. The Greeks appear intitled to the honour of the invention, so far at least as relates to bridges and aqueducts. The arched dome seems to have had its origin in Etruria. This kind of dome, it is conjectured, arose from its fitness for the accommodation of augurs, whose business it was to observe the flight of birds. Their stations for this purpose were templa, so called a templando, on the summits of hills. To shelter an augur from the weather, and at the Vol. V.

same time allow him a full prospect of the country around him, no building was so proper as a dome set on columns. In the later monuments and coins of Italy and Rome, it is common to find the Etruscan dome and the Grecian temple combined the celebrated Pantheon was of this form, even in its most ancient state. The arch is very frequent in the magnificent buildings of Rome, after the Roman conquests, such as the Coliseum, the Dioclesian baths, and the triumphal arches; where elegance of form was manifestly an object of attention. It will be seen that our opinion does not coincide with that of M. Dutens respecting the very early origin of the scientific construction of the arch: indeed, we conceive, that his citations, numerous as they are, cannot produce conviction in any mind accustomed to estimate the value of evidence.

But this kind of inquiry, however interesting, cannot be pursued here. Mr. Ware, by directing his attention to the theory of arches, naturally calls ours thither: and, as it is a subject which but seldom exercises the talents of either our mathematicians or our architects, we shall perhaps be excused by the general reader, if, for the sake of our scientific friends, we indulge in a short disquisition on the present occasion.

The simplest possible case of a covering to an edifice, that of a block of stone placed horizontally upon the top of two parallel vertical walls, gives little scope for the investigations of theorists. Let but the block hang over sufficiently and equally on the exterior side of each wall; and no weight, short of that which would crush the wall or the block, would by its vertical pressure on the middle of the roof endanger the structure. But, instead of a single block, suppose there were two equal ones which are to be set in a sloping direction from the top of each wall, and to meet in an angle or edge in the midway between the two walls: then it is evident, that some care will be requisite in the adjustment of the magnitude and weight of the blocks, their angle of inclination to the horizon, &c. that the lateral pressure, or thrust, should not be sufficient to force out the walls from their vertical position, and thus overset the whole. Conceive the sloping blocks separated by a horizontal block placed between them, so as to operate upon all below like a wedge, and the condition of equilibrium will again be changed. And if a fourth block be interposed, so as to give the whole the shape of what is now called a kirb roof, those conditions will of course receive another alteration. Let other blocks or stones be conceived superposed in a variety of ways,-so, for example, as to make the structure assume the shape of a polygon or a curve beneath, while it has a horizontal right line above; and the conditions of equilibrium will become still more complex. Now