Page:The American Cyclopædia (1879) Volume VII.djvu/339

 FORTIFICATION 331 terings made in the front. The cuts K K are made to isolate its extremities from the salient portion, and prevent the enemy from driving the defence from the redoubts of the reentering places of arms if he should gain possession of the demilune. The demilune redoubt J is for the purpose of sweeping at close range the terreplein of the demilune, and render its de- fence more obstinate by the support it receives from the redoubt. The covered way D D, bordering the ditches of the main work and demilune, forms a secure communication around the entire work. It is an indispensable out- work, and is of the highest importance where an active defence is to be made. Traverses, a,, are placed at intervals to protect the troops in it from ricochet fire, and are arranged for defence. The covered way is broken forward in the reentering angles for the purpose of enlarging the covered way at these points, and producing a flanking arrangement by which the glacis can be swept and a cross Glacis. GlacU Glacis. FIG. 2. A A A A, the enceinte or body of the place, or main enclosure; B B, the bastions; COCO, the main ditch, or the ditch of the enceinte; D D D D, the bastion and demilune covered ways; E E, the reentering places of arms; F. the salient place of arms; G, the demilune; H H, the demilune ditch; J, the demilune redoubt; K K, cuts in the demilune; L L, the ditch of the demilune redoubt; M M, the redoubts of the reentering places of arms; N N, ditches of the redoubts ; O, the tenaille ; P, double caponniere ; X X, exterior side ; a a, traverses of the covered way. fire brought to bear upon the ground in front of the salients. Within this enlarged space, or reentering place of arms, a redoubt M is placed. Its object is to strengthen the covered way and sweep with its fire the enemy's estab- lishments on the glacis of the demilune. Some- times a redoubt is placed in the salient place of arms. The surface of the embankment of the covered way is made, from the interior crest to the exterior, with a gentle slope. The principle to be attended to in arranging these glacis planes is, that they should all be swept by the artillery fire of the works in their rear, and by the musketry fire at least of the bastion face. From what has been said, it will be seen that in this system, when the relief and plan are suitably arranged, the fortification possesses the advantage of having its ditches thoroughly swept from within the main work itself, of bringing a cross and flank fire to bear upon the approaches on the salients, and fur- nishing a strong direct and cross fire upon the