In the thirteenth century walls and towers were provided with movable wooden scaffoldings, as shown at A in the figure. Spaces were left in the masonry of the walls for the insertion of wooden beams, which, projecting from the curtain, supported an overhanging gallery. This, being pierced with traps or apertures in the flooring, commanded the base of the wall, and was an important element in defensive operations. But as it was found that these timber galleries were easily set on fire by assailants, they were replaced in the fourteenth century by stone machicolations, as shown at B, consisting of corbels, supporting an embattled parapet. Between the inner face of the parapet and the outer face of the curtain the supporting corbels alternated with openings for the defence of the base, as already described. This arrangement, among the earliest examples of which are the square towers of Avignon, was soon generally adopted by architects in the construction of city ramparts. [Illustration: 170A. MACHICOLATIONS] "The art of fortification, which had made great advances at the beginning of the thirteenth century, remained almost stationary to the end of it. During the Hundred Years' War, however, it received a fresh impetus. When order had been restored in the kingdom, Charles VII. set about the restoration or reconstruction of many fortresses recaptured from the English. In the defensive works of such towns and castles, and in various new undertakings of a like nature, we recognise the method and regularity proper to an art based on well-defined principles, and far advanced towards mastery."[62] [62] Viollet-le-Duc, _Dictionnaire_, vol. i. In the Abbey of Mont St. Michel the successive modifications applied to military _enceintes_ from the thirteenth to the fifteenth century, are illustrated in the fullest and most interesting manner. [Illustration: 171. RAMPARTS OF ST. MALO (FIFTEENTH CENTURY)] Of the fourteenth century fortifications, which surrounded the original town at the summit of the rock, connecting the ramparts with the _Merveille_ on the north, and the abbey buildings on the south, some fragments still remain. The tower on the north is intact. The walls are crowned with machicolations, in accordance with the then novel system of massing the defences at the top of the ramparts. The gate of the _enceinte_ was to the south-east, judging from the miniatures in the _livre d'heures_ of Pierre II., Duke of Brittany, which show the arrangement of the original _enceinte_ at the close of the fourteenth century.