Tambour, a kind of work formed of palisades, 10 feet long, and 6 inches thick, planted close together, and driven 2 or 3 feet into the ground; so that when finished it has the appearance of a square redoubt cut in two. Loop-holes are made 6 feet from the ground, and 3 feet asunder, for the soldiers to fire through, who are placed on scaffolds 2 feet high. They have often been used by the French with great advantage.
Têtes-de-pont. See [Bridge-heads].
Trous-de-loup are holes dug in the ground, circular at top, about 4¹⁄₂ feet diameter, and 6 feet deep, pointed at bottom, like an inverted cone, or sugar loaf. A stake six feet long is fixed in their centre, driven 2 feet into the ground, and made sharp at top. Two or three rows of them are dug chequerwise, about 6 paces from the ditch of a field-work. They prevent the approach of horse, &c.
Perpendicular Fortification.
The principles of Vauban for direct or horizontal works, are the most perfect of all others: indeed all the masters of the art in modern times, who have introduced any thing new, allow that their works are only improvements of Vauban. The writings of Cormontagne are the most approved of the late writers on military defence. The principles of elevated works to cover naval roads and harbors, is among the improvements on Vauban; the works at Cherbourg, in France, and at fort Columbus, New York harbour, are very happy examples of the power of such works, as well as of the talents of the Engineers who erected them. Those at New York were by Col. Williams of the United States engineer corps.
Subterraneous Fortification.
These consist of the different galleries and branches which lead to mines, to the chambers belonging to them, or to fougasses, and which are required whenever it is found necessary to explode for the purposes of attack or defence. A subterraneous fortification may be of a permanent or temporary construction, offensive or defensive nature. Whenever this sort of work is adopted to strengthen and secure a fortified place, it is generally built of stone or brick, and made sufficiently solid to last a long time; it is then called permanent and defensive. Any place which is put in a state to withstand the subterraneous attacks of a besieging enemy, is said to be countermined.
When the besieger wishes to make an impression on a fortification of this sort, he must first construct galleries which he covers with wood, &c. He then practices offensive and temporary fortifications of the subterraneous sort. These works are well calculated to aid him in securing a lodgment for his subterraneous artillery, and in establishing chambers, fougasses, &c.
With respect to fortification in general, different authors recommend different methods; but the principal are those of Pagan, Blondel, Vauban, Coehorn, Belidor, Scheiter, and Muller.
It must, however, be constantly recollected by every engineer, that his views are not to be confined to the mere art of fortification. He ought further to know the use which different generals, in different periods, have made of natural strength and position; without an attention of this sort, he will fall very short of that extensive knowlege, which every military man, who aims at military fame, must be ambitious of acquiring. Chains of mountains, and volumes of water, together with the influence which different climates have upon the latter element, should always constitute a part of the natural system that ought to form an essential portion of his application. Hydrography will likewise assist him in this pursuit. To enlarge upon this important branch of geography, and to point out the great means which it affords of natural defence and offence in fortification, would be to exceed the limits of our present undertaking. We shall, therefore, refer our military readers to Belair’s Elemens de Fortification, and content ourselves with submitting a short account of the different authors who have either given original systems, or have greatly improved those that were already known. Independent of whom, may be named the following writers, who have likewise contributed to the general knowlege of fortification, viz. Errard, Deville, Belidor, D’Alembert, Cormontagne, Folard, Clairac, Muller, Robins, LeBlond, Didier, Marshal Saxe, Cugnot, Tielke, Landsberghen, Trincano, Fallios, Rosard, Belair, &c.