144 MILITARY SCIENCES. 



The military engineers of the middle ages, like our own, were required 

 to solve the problem, so to arrange their works that they should mutually 

 defend each other ; whence it followed that the interior works must com- 

 mand the exterior. Accordingly the fortifications of the middle ages 

 consisted usually of a ditch surrounding the whole place, of a closed circum- 

 scribing wall, and a place of retreat, in which the garrison could defend 

 themselves even when the wall was in possession of the enemy. In the 

 cities, whenever these were walled, there was a citadel for this purpose ; in 

 the castles, a tower, which was stronger than the rest, and independent of 

 the other parts of the fortification. 



In the fortification of the middle ages, which we must study in burghs and 

 castles, the following objects are to be considered : 



a. Ditches. The most ancient ditches were simple excavations without 

 revetment, at least on the outer side (joZ. 44, jig. 1 *), for on the inner the 

 vertically rising wall made the wall of the ditch. The outer side of the 

 ditch, the counterscarp, took the natural slope of the earth, and not until 

 later was this also made steep and revetted with masonry. Wherever it 

 was possible, the ditches were filled with water, but frequently there was in 

 the middle of the floor of the main ditch a narrower ditch, the cunette, 

 which alone was filled with water, while the rest of the ditch was dry {jig.\ ^). 

 The dry ditches were always thickly set with caltrops (/>/. 51, Jig. 54). 



b. Bridges. The passage over the ditch was by bridges, or rarely by 

 dikes crossing it. The most ancient bridges were simple ; very soon, how- 

 ever, wide drawbridges were constructed, in which one part was fixed and 

 one movable, so that it could be hoisted up. PL 44, Jig. 12, shows the 

 drawbridge of St. John's gate at Provins, from without ; Jig. 13, from 

 within. The draw part was attached by chains to two long beams, which 

 reached back inside of the gate, were pulled down at that end, and thus 

 raised up at the other, carrying the draw with them. If the draw was 

 very light, for foot passengers alone, it was constructed as in Jig, 11. If, 

 on the contrary, the river was very broad, and the bridge of stone, there 

 were usually one or more towers in the centre to afford a multifold and 

 enduring defence. PL 46, Jig. 1, shows a bridge thus secured at Sutri in 

 Italy. 



c. Outworks. To cover the bridge, a small fortification was erected on 

 the opposite bank, frequently only a breastwork with palisades, sometimes, 

 especially when a remote point of importance was to be secured, a sepa- 

 rate tower, which was connected with the main work by a subterranean or 

 other covered passage. PL 44, Jig. 14, shows the ground plan of such a 

 fortification (bridge-head) lying opposite the bridge of Vincennes ; Jig. 15 

 gives the elevation also. PL 46, Jig. 11, is the ground plan of the old 

 Louvre, where at F, such a bridge-head and detached work may be seen. 



d. Gates. The gates of old fortifications are almost always placed in a 

 very thick walls and flanked by two towers, so that the entrance could be 

 more readily defended. Often the gate is double, and between the two 

 there will be found a court inclosed by walls. The old gate of San 

 Vincente in Spain {fig. 2) shows such a court, and the gallery which con- 



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