[50] The making of a Roman road was a formidable enterprise. H. M. Scarth, in his “Roman Britain,” relates how a portion of the Fosse Road at Radstock, about ten miles south-west of Bath, was opened in February, 1881, and that its work showed the following details in constructive method. 1. Pavimentum, or foundation, fine earth, hard beaten in. 2. Statumen, or bed of the road, composed of large stones, sometimes mixed with mortar. 3. Ruderatio, or small stones well mixed with mortar. 4. Nucleus, formed by mixing lime, chalk, and pounded brick or tile; or gravel, sand, and lime mixed with clay. 5. Upon this completed foundation the summum dorsum, or surface of the paved road, was laid with infinite care. So the men of a day built roads for the centuries, and were proud to be servants to the unborn.
[51] Professor Fleeming Jenkin. If any reader wants to continue the study of timber bridges, let him turn to Colonel Emy and to the huge volumes compiled and edited by Hosking. But it is clear enough that timber bridges belong to the past; in these days they are ludicrously out of joint with the needs of social life, owing to the rapid advance which “progress” has made in artillery, in high explosives, in airships, and in aeroplanes.
[52] These date from about the year 1816, when Galashiels Bridge was constructed. It was only 112 ft. in length. But in 1819 Telford designed the Menai Bridge, in which the span of the catenary is 570 ft. and the dip 43 ft. The success of this work gave rise to much imitation, and in several places very great projects were carried through with success. At Pesth, for instance, the span was 666 ft., and at Fribourg 870 ft. But engineers, having no imagination and but little prudence, went too far, so they had to retreat from their cocksureness. Soon it became evident that a long suspended bridge of metal suffered much from the lateral oscillation caused by wind, and that its flexibility made it unfit for railway traffic. “The platform rose up as a wave in front of any rapidly advancing load, and the masses in motion produced stresses much greater than those which could result from the same weights when at rest. Moreover, the kinetic effect of the oscillations produced by bodies of men marching, or even by impulses due to wind, may give rise to strains which cannot be foreseen, and which have actually caused the failure of some suspension bridges. On the 16th of April, 1850, a suspension bridge at Angers gave way when 487 soldiers were passing, and of these 226 were killed by the accident.”—Professor Fleeming Jenkin.
[53] From information kindly supplied by the Rev. O. M. Jackson.
[54] “A Voyage to South America,” Antonio de Ulloa, translated from the Spanish by John Adams, Fourth Edition, Vol. II, p. 164.
[55] Such caves are frequent on the coast of Pembroke, in the Little England beyond Wales. Lydstep Arch is a far-famed example, and the Devil’s Punch Bowl, opened within the area of a prehistoric camp by the falling in of the roof, has an archway to the sea. “Bocherston Mere is a very small aperture, which, like a widening funnel, spreads out below into a large cavern. During the prevalence of gales from the south-west, the sea, driven by wind and tide in at the arched entrance, is ejected through the upper hole in jets of foam and spray some forty or fifty feet high, like geyser spouts. The limestone naturally pierced with caverns lends itself to be thus riddled and rent.”—S. Baring-Gould, “Book of South Wales,” p. 196.
[56] There is no need to multiply examples, for every reader must have seen how rocks have been vaulted, and lands tunnelled, by underground rivers. At one part of her course, for example, the Guadiana flows underground for twenty miles, forming a vast bridge above which 100,000 sheep can pasture.
[57] When the glacial theory of their formation was young and argumentative it encountered at first a sneering opposition from Sir Roderick Murchison, the famous geologist, who in 1864 wrote as follows to Sir William Denison: “In my anniversary address to the Geological Society you would see the pains I have taken to moderate the icemen, who would excavate all the rock-basins by glaciers eating their way into solid rocks.” But he failed to “moderate the icemen”; and Sir Roderick himself, a few years before his death, gave what is called “a tardy acquiescence” to their evidence. He became a frigid iceman. As Dr. Robert Munro has said, evidence which may be clear and convincing to one trained mind may not have the same effect on another—a fact which should at least warn us to be tolerant in matters of opinion.
[58] Dates in Egyptian history are obscure, but these give the period approximately.
[59] “Encyclopædia Britannica,” 11th edition, article “Arpino.”