Perronet, after considering this fact, wished abutment piers to be revived in a discreetly effective manner (_footnote_ p. 338), but their excellent advice was not followed. Defenceless bridges became fashionable everywhere, though they added innumerable anxieties to the perils of military war. The Valentré Bridge at Cahors should be studied as the best example of a mediæval battle-bridge, but the abutment piers might have been improved, 283-4. To-day a new era in bridge-building is heralded by rapid improvements in airships and aeroplanes; there should be a congress of architects and engineers to discuss the urgent questions of national defence that the piers and footways of bridges bring before our common sense, 335, 358. ABUTMENTS, the end supports of a bridge. ABYDOS, one of the most ancient cities of Upper Egypt; an early arch there in the temple of Rameses II, 155. ACARNANIA, the most westerly province of ancient Greece; early examples of the semicircular arch, 160. ACCIDENTS, THE, OF CIVILIZATION, they claim as many lives in a century as do the casualties on stricken fields, 34 _footnote_. ACCIDENTS TO OLD LONDON BRIDGE, 218. ADAM OF EVOLUTION, THE, had sense enough probably to lay a flat stone from bank to bank of a deep rivulet, 60; his personal appearance, 115-16; his character, 116, 117; his attitude to tree-bridges, 116; and to several other bridges made by Nature, 118-19. ADDY, SIDNEY O., his book on “The Evolution of the English House,” 139 _footnote_. ADRIAN IV, Pope, sanctioned in 1156 the building of a chapel on the Roman bridge over the Vidourle at Pont Ambroise in France, 82. ÆLIUS, PONS, built by Hadrian in A.D. 13, 194, 324. AEROPLANES, in their relation to bridge-building and national defence, vii, viii, 59, 335, 358. AFRICAN NATIVES, their tree-bridges and their want of initiative, 123, 148. AFON MYNACH, the cataract in South Wales, 67. AGOWE DISTRICT, Equatorial Central Africa, a primitive suspension bridge partly made with very thick vines, 148. AGRIPPA, son-in-law of Augustus Cæsar, the reputed founder of the Pont du Gard, about 19 years B.C., 174. AIRMEN SCOUTS, their relations to future wars, 335, 358. AIRSHIPS, their influence on bridge-building and on national defence, vii, viii, 59, 335, 358. AIRVAULT, DEUX-SÈVRES, Le Pont de Vernay, a famous bridge with ribbed arches, French Romanesque Period, Twelfth Century; See the colour plate facing page 96; and the remarks on ribbed arches, 93-100. ALAMERI, HALAF, a famous bridge-builder in Spain, 286-7. ALBARRACIN, in Aragon, its timber bridge with stone piers, 275. ALBI BRIDGE over the Tarn, famous in the history of pointed arches, 84, 86, 89, 90, 91, 92; See also the illustrations facing pages 72 and 92.