Part 46

The manner of making the materials for field works, may be seen under the heads _Fascines_, _Gabions_, _Hurdles_, &c. and the manner of estimating the quantity of materials for works of this kind, may be seen under the word _Battery_. See _Am. Mil. Lib._

FORTIFICATION...._Permanent_.

A parapet, to resist cannon should never be less than 18 feet thick in earth, and 8 or 9 in masonry. A wall need only be two feet thick in masonry to resist musquetry. The parapet should always be 4¹⁄₂ feet above the banquette, and 7¹⁄₂ or 8 feet above the rampart, or terre-plein.

The _Rampart_ should always be sufficiently wide to allow for the platform, and for two carriages passing each other; about 9 fathoms at top. A parapet of earth, though it takes more room, is always preferable to one of masonry, when it can be raised; though the only objection to the masonry, is the number of splinters it produces.

Entire _Revetements_ of masonry are not advantageous for the same reason. The masonry of revetments should not be so high as to be seen or battered from a distance; earth parapets are battered in vain, as the earth forms a natural slope.

The best _Scarp_ is made of masonry, either in wet or dry ditches, be the earthen one ever so well fraized or palisaded. The earthen one may be stormed without making a breach. The scarp should be 30 or 35 feet high.

The _Counterscarp_ should also be of masonry, and not less than 12 feet high. The inconveniences of an earth or low counterscarp, are the impossibility of defending to the last the covert way; as the enemy may descend into the ditch, and again mount the covert way, and so get in the rear of the traverses. The enemy may find his way along the natural slope of an earth counterscarp, and is not delayed by a tedious operation of getting into the ditch. Besides the natural slope of the end of an earth traverse prevents its effectually covering the covert way.

Ditches are generally 15 or 18 toises wide. Dry ditches are always preferable to wet ones, on account of the shelter they afford the troops, and the ready communication with the outworks, without the constant trouble and danger of bridges.

The _Covert way_ should be 5 toises wide; less would croud the troops, and more would allow room for the enemy to erect batteries in it.

The whole of the glacis should be seen, not only from the crest of the parapet, but from the embrasures in the parapet.

The _Tenaille_, must not be so high as to prevent the flank guns in one bastion seeing the breach that may be made in the collateral one.

_Ravelins_ are best without flanks; their faces directed to 10 toises from the shoulders of the bastions.

The crest of the parapet of the body of the place should be 8 feet above the crest of the glacis, to command it across a ditch of 15 or 20 toises.

The crest of the parapet of the ravelin is 3 feet lower than that of the body of the place, in order that it may be more effectually commanded from the place; and therefore to enable the parapet of the ravelin to command its own glacis, the ditch is only made 10 toises, and this glacis is a foot lower than that of the body of the place.

There must be an equilibrium of defence established through every front of a fortified place; for it will be needless to strengthen any particular front, if the others from their weakness be left exposed. The following remarks may enable an observer to appreciate the value of particular works, in the proper application and arrangement of which that equilibrium consists.

_Intrenchments_ within the works add much to their defence. In large bastions with obtuse flanked angles, the best intrenchment is formed of the front of a fortification, or of two demi-bastions and a curtain, connecting the angles formed by the flank and curtain. If this intrenchment be advanced to the shoulders of the bastion, so as to include its flanks, as is often the case, it will be subject to be taken in the rear, by the fire from the counter batteries opposed to the flanks. But in bastions with acute flanked angles which do not afford sufficient space for this kind of intrenchment, Cormontaigne proposes one in the form of a cavalier, whose faces and flanks are parallel to those of the bastion. The first kind of intrenchment does not operate in the defence of the place, till after the passage of the ditch; till which time it remains entire, and then capable of a very great defence. The second kind becomes a support to the bastion from the first commencement of the siege; but it is therefore subject to have its defence destroyed at a distance. Nor is its defence equal to that of the other form.

_Counterguards_ should possess the three following properties: 1st. They must cover effectually the principal work before which they are placed; at least that part of it, which can be battered in breach. 2d. They must be lower than the work which they cover; but not so low as to permit its revetement to be seen. 3d. They must be so narrow as not to afford room for the besiegers to erect batteries in them, against the work which they cover, and therefore not leave the besiegers a choice of positions. The counterguards in Coehorn’s system are only of earth, through which it is necessary to make an opening, before the capital work can be battered.

_Horn_ or _Crown works_, unless to occupy some important point, to strengthen some weak side, or to afford more room for a confined garrison are rather a weak than a strong arm to a place. This is particularly the case when they are constructed with smaller, and consequently weaker fronts, than that part of the body of the place which they cover: as they facilitate, when taken, the approaches to the body of the place. This is remedied by constructing their fronts of the same strength as the front or fronts which they cover. They also facilitate the taking of the place, by exposing the revetement of the work on which their branches are directed to be battered in breach, along the ditches of those branches. This is a great evil, even to an outwork, but is of serious consequence if they rest upon the body of the place. This defect has been remedied by placing these works altogether outside of the covert way, and allowing their ditch no communication with those in the rear. In this case their gorge must be made very secure to prevent its being turned.

An _Advanced Covert way_, is esteemed amongst the best means of adding to the defence of places. Besides the advantages common to the usual covert way, it has many peculiar to itself. It however seems necessary to ensure to it the many advantages of which it is susceptible, (beside being properly palisaded,) that it should be secured in the rear by a wet ditch, as the only means of giving it an inaccessible counterscarp, and at the same time keeping it under the fire of the musquetry of the place. This kind of covert way is generally supported by redoubts upon the capitals of the bastions and ravelins which from their position cannot mask the fire of the place; and being mounted with artillery, oblige the besiegers to commence their attack at a great distance, and very much to extend their operations; and as their establishment upon this covert way must effectually mask the fire of their first batteries, it must greatly increase their labor. The retreat from these redoubts must be secured by an underground passage.

_Countermines_ are undoubtedly one of the first means of strengthening places. For this article we refer to the word _Mines_.

_Detached redoubts_, when circumstances of situation favor them, are employed with great success. They are usually detached and totally unconnected with any of the works of the place, by any covert way or other above ground work; and have for objects, either the opposing an additional obstacle to the besiegers at the point they occupy, or the rendering the adjoining fronts inaccessible, by an enfilade or reverse fire upon the approaches. They also afford at their gorge, a most excellent rendezvous and retreat for sorties; upon the level of the country, and without the difficulty of filing troops through the barrier of a covert way.

But in order to insure to the detached work or works, all these advantages, it is necessary that they should be either totally inaccessible to the besiegers, by reason of the natural difficulties of their situation, as in an inundation, morass, &c. or be made secure by art, from being taken by storm, and only attackable by regular approaches. They should be under cover of the fire of the place; but if their distance be too great for that, an intermediate work must be established to give them support. Their best form is that of a bastion with retired flanks; and a strong system of countermines the most effectual way of prolonging their resistance.

_General remarks_...The larger the flanked angles of works, the more direct will be their fire, and that of their covert way, upon the approaches; the greater extent will they oblige the besiegers to occupy in their parallels and batteries; and the more will they oblige the besiegers to expose themselves to the fire of the fronts collateral to the one attacked. Faces of works directed to inaccessible situations, such as rivers, lakes, &c. from whence they cannot be enfiladed by ricochet batteries, add greatly to the strength of a front.

If the flanked angle of a ravelin be so advanced as to see in reverse any battery erected upon the crest of the glacis, or in the covert way of the bastions, it will increase the strength of that front; because it will oblige the besiegers to gain possession of the ravelin, before they can make any lodgment, from which they can batter the bastions. This is the case in Cormontaigne’s system: and a place thus fortified, obliges the besiegers to attack and gain two ravelins to get at the bastion between them. Beside, if this system be applied to a right line, or to a polygon of many sides, the prolongations of the faces of the bastions will be intercepted by the flanked angle of the ravelins, and consequently make the establishment of enfilading batteries against them very difficult. A work which admits of a breach being made in it (particularly the body of the place) at a distance, very much facilitates its being taken. The ditch of the ravelin affords an opening through which the besiegers may make a breach in the face of the bastion from the glacis, opposite the flanked angle of the ravelin, and is therefore subject to this defect. A counterguard before the bastion, lessens this evil, by transferring the breach from the body of the place to the ravelin; but it requires a counterguard also before the ravelin, effectually to cure it. A crown or horn work also produces this evil; its remedy was given, in speaking of those works.

The direction of the flanks or faces of a work is not so material as relating to the fire of artillery, as to that of musquetry; for artillery is never fired without being pointed, but musquetry is fired mechanically, and perpendicular to the parapet, without much attention to the object to be struck.

A work in the neighborhood of a height must be defiladed[8] from that height, that is, instead of being built upon a horizontal plane, it must be erected upon an imaginary inclined plane, passing from somewhere in the interior of that work, over the most commanding points of the height: and every part of the works must bear the same relation to this inclined plane, that they would do, to a horizontal plane in a level country.

[8] _The French use the word_ defile _in a contrary sense to_ enfile; _and as we admit the words enfilade and enfiladed from the latter, we cannot refuse the terms defilade and defiladed from the former_.

A work is not therefore always to be condemned, because it is in the neighborhood of a height; for if it be properly defiladed from that height, it will receive a great advantage over the approaches of the besiegers, carried on down an inclined plane towards it. But a work to be properly constructed in the neighborhood of heights, must not uniformly preserve the same distance from those heights, unless their summits be all upon the same level; but must approach them at their lowest parts, and recede from them as they rise; thus will the necessary plane of defilement preserve nearly the same degree of obliquity throughout.

_Dimensions of Walls and their Counterforts, from 10 to 50 Feet high, having a Slope of ¹⁄₅ their Height._

+---------------------------+-------------------------+ | Wall. | Counterforts. | +-------+---------+---------+--------+--------+-------+ | |Thickness|Thickness|Distance| | | | | at | at | between| | | |Height.| Top. | Bottom. | them. |Breadth.|Length.| +-------+---------+---------+--------+--------+-------+ | Ft. | Ft. In. | Ft. In. | Feet |Ft. In. |Ft. In.| | 10 | 4 0 | 6 0 | 8 | 2 8 | 4 -- | | 15 | 4 3 | 7 3 | 10 | 3 4 | 5 -- | | 20 | 4 6 | 8 6 | 12 | 4 0 | 6 -- | | 25 | 4 9 | 9 9 | 14 | 4 8 | 7 -- | | 30 | 5 0 | 11 0 | 16 | 5 4 | 8 -- | | 35 | 5 3 | 12 3 | 18 | 6 0 | 9 -- | | 40 | 5 6 | 13 6 | 20 | 6 8 |10 -- | | 45 | 5 9 | 14 9 | 22 | 7 4 |11 -- | | 50 | 6 0 | 16 0 | 24 | 8 0 |12 -- | +-------+---------+---------+--------+--------+-------+

The heights in the above table are taken only from the bottom of the ditch, and do not include the foundations.

When the rampart is partly walled and partly turfed; then ¹⁄₅ of the height of the turfed part must be added to the breadth of the wall at the top given in the table.

The bases of all inward slopes of earth should be equal to their height, if not more.

The bases of all outward slopes of earth ²⁄₃ of their height.

The superior slopes of all parapets ¹⁄₆ of their breadth.

The slope of all walls, or revetements ¹⁄₅ of their height.

Though the above principles given for the erection of field works may assist an officer’s recollection who may be employed on that duty, the memorandums given respecting _permanent_ fortification pretend to no such object: but may serve to remind an officer, if he should visit a fortification, of its essential requisites; and may assist his observations in passing round the works.

FORTIN, FORTLETT, or FORTILAGE. See FIELD-FORT.

FORTRESS, any place strongly fortified.

FORWARD, a word of command, which is given when a regiment, or company has been interrupted in its regular movement, and the march is continued. On this occasion every succeeding division must preserve its proper distance and mark time until the word _Forward_, is given. This frequently occurs in the passage of obstacles, and in the winding of roads, streets, &c.,

_Right_ or _Left_ _shoulders_ FORWARD, an absurd word of command, used in the British exercise. It is a gross misconception of the French _line of science_, which requires the whole body to face in the given inclination; every man must see that it is impossible for a soldier to march either with ease or grace in such a position. See LINE OF SCIENCE.

FOSSE, in fortification. See DITCH.

FOSSES _pleins d’eau_, _Fr._ Wet Ditches. See FORTIFICATION.

FOSSES _secs_, _Fr._ Dry ditches.

FOSSES _revétus_, _Fr._ Ditches that are lined.

FOSSES _non revétus_, _Fr._ Ditches that are not lined.

FOUCADE, FOUGADE, a small mine.

FOUGASS, in _mining_, a small mine, from 6 to 8 feet under ground: It is generally placed under the glacis or dry ditches.

FOUGETTE. _Fr._ Indian sky-rocket, a species of fire-work which is frequently used by the Asiatics. The author of a late military production in France makes the following observations relative to advantages which might be derived from this weapon against cavalry, and for the defence of fortified places, or intrenchments. He observes, that the fougette, in shape, resembles a sky-rocket, whose flight is gradually brought to run along an horizontal direction. By throwing several fougettes into parks of artillery and upon the caissons, &c. considerable damage might be occasioned from the fire which would inevitably be communicated to some part. A fougette forces itself immediately forward, cuts as it penetrates, by the formation of its sides, which are filled with small spikes, becomes combustible and on fire at all its points; and possesses within itself a thousand various means by which it can adhere to whatever object it is destined to set on fire or to destroy. This weapon would be more effectual, because it might be more variously applied, to defend the mouth of a harbor against an enemy’s shipping, than red-hot balls can ever prove. Fougettes might be used on board ships of war, but there would certainly be some danger in the experiment; although, in my humble opinion, a little experience would effectually remove that difficulty; in which case ships might run along a coast, and easily destroy the wooden works that are sometimes erected upon it. They would in the first place occasion more havoc than red-hot balls; and in the next, they might be used whilst the vessel was in full sail; which cannot be done in the first instance. By means of their natural velocity they would do more execution in a less space of time, than the most active piece of ordnance could effect; and they would require fewer hands, as the only necessary operation would be to light and dart them forward. As a defensible weapon it must naturally be allowed, that, where a small body of men is attacked, the fougette might be adopted with considerable advantage.--The writer of this article, who, we find, is likewise the inventor of a fougette which has been submitted to the French government, continues to argue much in favor of its adoption. If, adds he, our enemies should imitate the invention, we must then have recourse, especially in sea-fights to those pieces of ordnance which are calculated to do more execution at a distance; and it will then be our business to contrive fougettes that shall reach their shipping, by means of a greater degree of force and velocity which might be given to them, than they would be capable of attaining. See ROCKET.

FOUILLER, _Fr._ To search. In a military sense, it signifies to detach small bodies of infantry round the flanks of a column that is marching through a wood, for the purpose of discovering an ambuscade, and of giving timely notice that it may be avoided. The same precaution is necessary when a body of men advances towards or enters a village.

FOUNDATION, in military architecture, is that part of a building which is under ground, or the mass of stone, brick, &c. which supports a building, or upon which the walls of a superstructure are raised: or it is the coffer or bed dug below the level of the ground, to raise a building upon; in which sense, the _foundation_ either goes to the whole area or extent of the building, as when there are to be vaults, galleries, casemates, or the like; or is drawn in cuts or trenches, as when only walls are to be raised. Sometimes the _foundation_ is massive, and continued under the whole building, as in the antique arches and aqueducts; but it is more usually in spaces, or intervals; in which latter case, insulated pillars, bound together by arches, should be used.

There are several things to be well considered in laying the _foundation_ of a military building. We must first examine the bed of the earth upon which we are to build, and then the under fillings or substruction. We are not to rest upon any seeming solidity, unless the whole mould through which we cut has likewise been solid; and in such cases, allow ¹⁄₆th part of the height of the building for the hollowing or under-digging, unless there be cellars under ground, in which case it may be something less. There are many ways to try the firmness of the ground; but the following, in our opinion, is the best. Take an iron crow, or such a borer as well-diggers use, which at once will point out the goodness and tenacity of the ground.

Engineers should use the utmost diligence in this point; for, of all the errors that may happen in building, those are the most pernicious which are committed in the foundation, because they bring with them the ruin of the whole building; nor can they be amended without very great difficulty.

FOUNDATIONS are either natural, or artificial: natural, as when we build on a rock, or very solid earth; in which case we need not seek for any other strengthening; for these, without digging, or other artificial helps, are of themselves excellent _foundations_, and most fit to uphold the greatest buildings. But if the ground be sandy or marshy, or have lately been dug, in such case recourse must be had to art. In the former case, the engineer must adjust the depth of the _foundation_ by the height, weight, &c. of the building: ¹⁄₆th part of the whole height is looked upon as a medium; and as to the thickness, double that of the width of a wall is a good rule. If you build upon mossy and loose earth, then you must dig until you find sound ground. This sound ground, fit to support a building, is of divers kinds: in some places so hard, as scarcely to be cut with iron; in other places very stiff; in other places blackish, which is accounted the weakest; in others like chalk, and in others sandy: but of all these, that is the best which requires most labor in cutting or digging, and when wet, does not dissolve into dirt.

If the earth to be built upon is very soft, as in moorish grounds, or such that the natural _foundation_ cannot be trusted, then you must get good pieces of oak, whose length should be the breadth of the trench or about 2 feet longer than the wall; these must be laid across the foundation about 2 feet asunder, and being well rammed down, lay long planks upon them; which planks need not lie so broad as the pieces are long, but only about four inches on a side wider than the basis, or foot of the wall is to be. But if the ground be so very bad, that this will not do, then you must provide good piles of oak of such a length as will reach the good ground, and whose diameter must be about ¹⁄₁₂th part of their length. These piles must be driven down by an engine for that purpose, and must be placed as close as one can stand by another; then lay planks upon them, and pin them fast. But if the ground be faulty in some parts, and firm in others, you may turn arches over those loose places, which will discharge them of the weight. You must not forget to place the piles under the inner, as well as the outer walls; for if these should sink, it would be a means to make the outer walls crack, and so ruin the whole building.