FORTIFICATION. 495 



behind the parapet, is called the terre-pleine ; which is sometimes 

 lowered, by excavation : and if there be a large central space, it is 

 called the parade ground. 



A redan, (PL XL, Fig. 2), is a triangular work, two sides of 

 which, called faces, are fortified ; while the third side, or gorge, 

 towards the rear, is often left open. A small redan, is sometimes 

 called a fleche, or arrow. A bastion, (Fig. 3), has a salient angle, 

 and two faces, in front; connected with two shorter lines, called 

 flanks, which are less divergent, and extend to the gorge ; this latter 

 being either open, or palisaded, or completely intrenched. A small 

 bastion is also called a lunette. A bonnet, mitre, or swallow tail, 

 (Fig. 4), has two salient angles in front, as if it were two redans 

 united, side by side, with a common gorge. These different works 

 are sometimes associated, to form a fortified line, or lines ; whether 

 separate, but defending each other by their fires ; or connected, by 

 intermediate trenches, from gorge to gorge. Any one of these 

 works, completely enclosed, is called a redoubt; and a work which 

 is large enough to admit of flanking arrangements, so that one side 

 may enfilade, or fire along the ditch of another side, to defend it, is 

 called a field fort. When the work is designed for receiving can- 

 non, it is often called a battery; the cannons firing through cross- 

 cuts in the parapet, called embrasures; the high parts between 

 which, called merlons, serve to protect the men. 



Field works may be farther protected, by palisades, or rows of 

 stakes, presenting their sharp points outward, along the scarp, or in 

 the ditch ; as also by wolf-pits, or holes dug close to each other 

 alo-ng the exterior ; or by abattis, which are fallen trees, placed with 

 their top ends outward, to impede the enemy, while he is exposed to 

 the fire of the work ; or by chevaux-de-frise, (wooden horses), 

 which are timbers, armed with stakes, projecting in various direc- 

 tions, for the same purpose. Marshes, ponds, deep streams, preci- 

 pices, and other natural obstacles, are often resorted to, in aid of the 

 defence ; the great object of which, is to prevent the access of the 

 enemy. A work on low ground, is said to be commanded, when it 

 is overlooked by any other work or ground, so as to be exposed to a 

 fire therefrom. From such heights, the position, if it is an import- 

 ant one, should be defiladed ; by making the exposed side the high- 

 est, so that it may shelter the other side. 



2. Permanent Fortifications, or fortresses, are stronger forts, 

 usually built in masonry, around cities, or on the frontiers of coun- 

 tries, and designed for permanent use. The immediate object of a 

 fort, is to separate the defenders, or garrison within it, from the 

 enemy without; whose superior numbers are thus kept in check. 

 This is effected by means of a high wall ; on the outside of which 

 is usually a deep ditch ; both of them extending quite around the 

 fort ; of which they form a principal part. The ditch varies, in dif- 

 ferent works, from 12 to 20 feet in depth, and from 30 to 100 feet 

 in width ; but it should always be too wide to admit of crossing it 

 by ladders or portable bridges. The wall within the ditch, is called 

 the scarp : and is usually made about 30 feet high ; so that it cannot 

 be easily scaled, if vigilantly guarded. As the scarp is built up from 



