Note 9 — Chapter I · ROADS AND BRIDGES

This practice was inherited from the Roman builders, whose formularies continued to be transcribed throughout the middle ages. See Victor Mortet: “Un Formulaire du VIIIe siécle pour les fondations d’édifices et de ponts d’après des sources d’origine antique,” in “Bulletin monumental . . . de la Société française d’Archéologie,” vol. 71, 1907, p. 443. The brief chapter in the “Mappæ Clavicula” (still copied in the twelfth century), entitled “De fabrica in aqua,” recommends that, “Si fabricam in aqua necesse fuerit erigere, facis arcam triangulam,” arca meaning caisson. In this we see, Mr. Mortet writes, “la disposition venue de l’antiquité, transmise et maintenue au moyen-âge, de la forme prismatique triangulaire des avant-becs des ponts” (p. 461). This characteristic was conspicuous, e.g. in the Avignon and London bridges (see the picture, p. 45) as well as in the famous Roman Pont du Gard.