Piers of Bridges, [114], [200], [264], [316], [338], [341], [342], [353], [354]. There are other references also, but the reader will be able to follow the history of piers from the natural bridge of stepping-stones through the many changes and defects mentioned in the text. To-day, with the rapid improvements in airships and aeroplanes, new armoured piers will have to be designed, strong enough to bear the great weight of a roofed superstructure of armour-plate steel, yet not thick enough to obstruct rivers. Now that bridges are as vulnerable as Zeppelin sheds, engineers have an excellent chance to serve their countries well by inventing new and powerful bridges. How to protect piers—at least as much as possible—from direct artillery fire is one very difficult problem; how to protect them from falling shells and bombs is another. When London is fitted adequately with new defensive bridges her river will be as impressive as a fleet of super-Dreadnoughts. See also [“Abutment Piers.”]

Pisa, her chapelled bridge, [209]. The late Mr. S. Wayland Kershaw wrote as follows in 1882: “The most remarkable bridge chapel abroad is the one dedicated to Santa Maria del’ Epina on the side of the bridge over the Arno at Pisa, erected about 1230. Built of the rich stone and marble of the district, it is ornamented with niches and figures, and, though renovated and repaired, still presents a graceful appearance.”

Pontist Brothers or Friars, or Frères Pontifes, [83], [90], [91], [92], [296], [297], [342]. St. Bénézet was one of the leaders in this religious brotherhood of good craftsmen.

Many railway bridges over strategical rivers can be displaced by tunnels, but many others must be armoured with cone-shaped roofs as a protection against overhead wars from airships and aeroplanes, [358]. See Albi Railway Bridge, the plate facing page [8], and Cannon Street Railway Bridge, the plate facing page [48].

Rameses II, Temple of, at Abydos, has a primitive vault built with horizontal courses of stone, showing its descent from the rock archways made by Nature, [155].

Relief Bays for Flood Water, they were introduced by the Romans, 284, and were copied by mediæval bridgemen; witness the Pont des Consuls at Montauban, [255], [256], and the Pont St. Esprit, [293], [297]. Pontists should note both the difference of shape in flood-water bays and the variation of their position in the architecture. At Mérida, for example, in the great squat Roman bridge, they are long and round-headed, and rise from the low and bold cutwaters, which are overgrown with grey-green mosses and grass. On the other hand, a Moorish bridge of four arches near Tangier has much smaller relief bays with round heads, and they are pierced high up through the spandrils. They look like three little windows that give light and air to a work of sun-bleached antiquity. Moreover, their shape is repeated in about a dozen little holes cut through the base of the parapet, perhaps to help in the drainage of the roadway, perhaps to be useful in military defence. This Moorish bridge has semicircular arches, and the road is inclined over each abutment, just like the Roman bridge at Rimini. But the technical sentiment is less virile than the Roman.