Chapter D: Caldwell, (19)

_Flank of the bastion_, is the part between the face and the curtain; the flank of one bastion serves to defend the ditch before the curtain and face of the opposite bastion.

_Flanking_, is the same thing in fortification, as defending.

_Retired flanks_, are those made behind the line which joins the extremity of the face and the curtain, towards the capital of the bastion.

_Concave flanks_, are those which are made in the arc of a circle.

_Direct, or grazing flank_, is that which is perpendicular to the opposite face produced, and oblique or fichant, when it makes an acute angle with that face.

_Second flank._ When the face of a bastion produced does not meet the curtain at its extremity, but in some other point, then the part of the curtain between that point and the flank, is called the second flank. The modern engineers have rejected this method of fortifying. See FLANK.

_Flêche_, a work of two faces, often constructed before the glacis of a fortified place, when threatened with a siege, in order to keep the enemy as long at a distance as possible.

_Gallery_, is a passage made under ground, leading to the mines: galleries are from 4¹⁄₂ to 5 feet high, and about 3¹⁄₂ or 4 feet broad; supported at top by wooden frames, with boards over them.

_Genouilliere_, the undermost part of the rampart of a battery, or that part from the platform to the sole of the embrasures.

_Glacis_, is the part beyond the covert way, to which it serves as a parapet, and terminates towards the field in an easy slope at any required number of fathoms distance. Sometimes double glacis are made parallel to the esplanade, and at the distance of 16, or 20 fathoms.

Some authors think these works never answer the expence; however, M. Vauban was so sensible of their utility, that he never failed to make them when the ground was convenient for it; because, when such works are defended by a skilful governor, they will afford the means of being valiantly supported.

_Gorge_, of a bastion, is the interval between the extremity of one flank and that of the other.

_Gorge_, of any work, is that part next to the body of the place, where there is no rampart or parapet; that is, at the counterscarp of the ditch.

_Half-moon._ (_Fr._ _Demi-Lune_.) Is an out-work that has two faces which form a saliant angle, the gorge of which resembles a crescent. It owes its original invention to the Dutch, who use it to cover the points of their bastions. This kind of fortification, is, however, defective, because it is weak on its flanks. Half-moons are now called ravelins; which species of work is constructed in front of the curtain. See RAVELINS.

_Gorge of a half moon_, the distance between the two flanks, taken on the right of the counterscarp.

_Head of a work_, its front next the enemy, and farthest from the place.

_Horn-work_, is composed of a front and 2 branches: the front is made into 2 half bastions and a curtain: this work is of the nature of a crown-work, only smaller, and serves for the same purposes. The use of horn-works in general is to take possession of some rising ground advanced from the fortification; the distance of which determine that of the horn-work; and they are placed either before the curtain, or before the bastions, according to circumstances.

_Horse-shoe_, is a small round or oval work, with a parapet, generally made in a ditch, or in a marsh.

_Insult._ A work is said to be _insulted_, when it is attacked suddenly and openly.

_Interior side of a fortification_, an imaginary line drawn from the centre of one bastion to that of the next, or rather the curtain produced till they meet.

_Lodgment_, See SIEGE.

_Loop-holes_, are either square, or oblong holes, made in the wall, to fire through with musquets. They are generally 8 or 9 inches long, 6 or 7 inches wide within, and 2 or 3 feet without; so that every man may fire from them direct in front, or oblique to right or left, according to circumstances.

_Lunettes_ in fortification, are works made on both sides of a ravelin: one of their faces is perpendicular to half or ²⁄₃ds of the faces of the ravelin, and the other nearly so to those of the bastion.

There are likewise lunettes, whose faces are drawn perpendicular to those of the ravelin, within ¹⁄₃ part from the saliant angle; whose semi-gorges are only 20 fathoms.

These kind of works make a good defence, and are of no great expence; for as they are so near the ravelin, the communication with it is very easy, and one cannot well be maintained till they are all three taken.

_Lunettes_, are also works made beyond the second ditch, opposite to the places of arms: they differ from the ravelins only in their situation.

_Lunettons_, are small lunettes.

_Merlon_, is that part of the breast-work of a battery which is between the embrasures.

_Orillon_, is a part of the bastion near the shoulder, which serves to cover the retired flank from being seen obliquely: it is sometimes faced with stone, on the shoulder of a casemated bastion, to cover the cannon of the retired flank, and hinder them from being dismounted by the enemy’s cannon.

Of all the works in a fortification, there is none more capable of defending the passage of the ditch, and to destroy the miner, wheresoever he enters himself, than the orillon. Experience in the last war has shewn us of what vast advantage it is to have 2 or 3 reserve pieces of cannon, which command the ditch, and the face of the opposite bastion, in such a manner as to destroy the attempts of the miners, and see the breach in reverse. Hence the great advantages of a double flank thus concealed weigh so very much with us, and convince us so entirely of their usefulness, that we affirm no place to be well fortified without the orillon, and that the straight flank is fit for nothing but field works.

The orillon is as old as the bastion, and was first made use of about the year 1480; and we find it frequently mentioned in the works of Pasino and Speckle, first published in 1579.

_Out-works._ See WORKS.

_Palisades_, in fortification, are a kind of stakes made of strong spars about 9 feet long, fixed 3 deep in the ground, in rows about 6 inches asunder: they are placed in the covert-way, at 3 feet from, and parallel to the parapet of the glacis, to secure it from being surprised.

_Parapet_, in fortification, is a part of the rampart of a work, 18 to 20 feet broad, and raised 6 or 7 feet above the rest of the rampart: it serves to cover the troops placed there to defend the work against the fire of the enemy.

_Parallels._ See SIEGE.

_Port-cullice_, in fortification, is a falling gate or door, like a harrow, hung over the gates of fortified places, and let down to keep out the enemy.

_Place_ is the term commonly used in fortification instead of a fortified town.

_Regular place_, one whose angles, sides, bastion, and other parts are equal, &c.

_Irregular place_, one whose sides and angles are unequal, &c.

_Place of arms_, in fortification, is a part of the covert-way, opposite to the re-entering angle of the counterscarp, projecting outward in an angle. It is generally 20 fathoms from the re-entering angle of the ditch on both sides, and the faces are found by describing a radius of 25 fathoms.

_Places of arms._ See SIEGE.

_Pits_, or _ponds_, in fortification, are little holes dug between the higher and lower curtains, to hold water, in order to prevent the passing from the tenailles to the flanks.

_Profiles_, in fortification, are a representation of the vertical sections of a work; and serve to shew those dimensions which cannot be described in plans, and are yet necessary in the building of a fortification; they may be very well executed and constructed upon a scale of 30 feet to an inch. By a profile are expressed the several heights, widths, and thicknesses, such as they would appear were the works cut down perpendicularly from the top to the bottom. See PROFILES.

_Rampart_, is an elevation of earth raised along the faces of any work, 10 or 15 feet high, to cover the inner part of that work against the fire of an enemy: its breadth differs according to the several systems upon which it may be constructed: for De Ville makes them 12¹⁄₂ fathoms, M. Vauban 6, and others 10 fathoms.

_Rams-horns_, in fortification, are a kind of low work made in the ditch, of a circular arc; they were first invented by Mr. Belidor, and serve instead of tenailles.

_Ravelin_, in fortification, is a work placed before the curtain to cover it, and prevent the flanks from being discovered sideways, it consists of 2 faces meeting in an outward angle. Some ravelins are counter-guarded, which renders them as serviceable as either the cunettes, or tenaillons.

_Gorge of the ravelin_, is the distance between the two sides or faces towards the place.

_Gorges_, of all other outworks, are the intervals or spaces which lie between their several wings or sides towards the main ditch. See GORGES.

_Redans_, in fortification, are a sort of indented works, consisting of lines or facings that form sallying or re-entering angles, flanking one another, and are generally used on the sides of a river running through a garrisoned town. They were used before bastions. Sometimes the parapet of the covert-way is carried on in this manner.

_Redoubt_, is a kind of work placed beyond the glacis, and is of various forms. Its parapet, not being intended to resist cannon, is only 8 or 9 feet thick, with 2 or 3 banquettes. The length of the sides may be from 10 to 20 fathoms.

_Redoubt_, is also the name of a small work, made sometimes in a bastion, and sometimes in a ravelin, of the same form.

_Redoubt_, is likewise a square work without any bastions, placed at some distance from a fortification, to guard a pass or to prevent an enemy from approaching that way.

_Detached-redoubt_, is a kind of work much like a ravelin, with flanks placed beyond the glacis: it is made to occupy some spot of ground which might be advantageous to the besiegers; likewise to oblige the enemy to open their trenches farther off than they would otherwise do. Their distance from the covert-way should not exceed 120 toises, that it may be defended by musquet shot from thence.

_Redouts-en-cremaillere_, so called from their similitude to a saw; the inside line of the parapet being broken in such a manner, as to resemble the teeth of a saw; whereby this advantage is gained, that a greater fire can be brought to bear upon the defile, than if only a simple face was opposed to it, and consequently the passage is rendered more difficult.

_Retrenchment_, in fortification, is any work raised to cover a post, and fortify it against an enemy, such as fascines loaded with earth, gabions, sand-bags, &c.

_Revetement_, in fortification, is a strong wall built on the outside of the rampart and parapet, to support the earth, and prevent its rolling into the ditch. When the revetement of a rampart goes quite up to the top, 4 feet of the upper part is a vertical wall of 3 feet thick, with a square stone at the top of it, projecting about 5 or 6 inches, and a circular one below, or where the slope begins, of 8 or 10 inches diameter. They go quite round the rampart, and the circular projection is called the _cordon_.

_Rideau_, in fortification, is a small elevation of earth, extending lengthways on a plane, and serving to cover a camp, or to give an advantage to a post. They are also convenient for the besiegers of a place, as they serve to secure the workmen in their approaches to the foot of a fortress.

_Rideau_ is also used sometimes for a trench, the earth of which is thrown up on its sides, to serve as a parapet for covering the men.

_Sap._ See SIEGE.

_Scarp_, is, properly speaking, any thing high and steep, and is used in _fortification_ to express the outside of the rampart of any work next to the ditch.

_Sillon_, in fortification, a work raised in the middle of a ditch to defend it when too broad. This work has no particular construction, but as it runs, forms little bastions, half moons, and redans, which are lower than the rampart of the place, but higher than the covert way. It is not much used at present.

_Sillon_ means literally a furrow. In fortification, it is a work raised.

_Swallow’s-tail_, a kind of out-work, only differing from a single tenaille, in that its sides are not parallel as those of the tenaille, but narrower towards the town than towards the country.

_Talus_ signifies a slope made either on the outside or inside of any work, to prevent the earth’s rolling down; it is of various denominations, viz.

_Talus of the banquette_ is that gentle slope from the top of the banquette to the horizontal line.

_Interior talus of the parapet_, the slope from the top of the parapet to the banquette.

_Talus of the top of the parapet_, that slope which lessens the height of the parapet towards the berm, by which means the troops firing from the banquette can defend the covert way.

_Exterior talus of the parapet_, the slope of the parapet from the top to the berm.

_Interior talus of the ditch_, the slope from the top of the ditch to the bottom, within.

_Tenailles_ are low works made in the ditch before the curtains; of which there are three sorts. The first are the faces of the bastion produced till they meet, but much lower; the second have faces, flanks, and a curtain; and the third have only faces and flanks. Their height is about 2 or 3 feet higher than the level ground of the ravelin. Their use is to defend the bottom of the ditch by a grazing fire, as likewise the level ground of the ravelin, and especially the ditch before the redoubt within the ravelin, which cannot be defended from any other quarter so well as from them.

_Tenaillons_ are works made on each side of the ravelin, much like the lunettes; with this difference, that one of the faces in a tenaillon is in the direction of the ravelin; whereas that of the lunette is perpendicular to it.

_Terre-pleine_, in fortification, the horizontal superficies of the rampart, between the interior talus and the banquette. It is on the _terre pleine_ that the garrison pass and repass; it is also the passage of the rounds.

_Tower bastions_ are small towers made in the form of bastions; first invented by M. Vauban, and used in his second and third method; with rooms or cellars underneath, to place men and artillery in them. As these towers are almost a solid piece of masonry, they must be attended with great expence, though their resistance can be but little; for it has been found by experience, that the casemates are but of little use, because as soon as they have fired once or twice, the smoke will oblige the defenders to leave them, notwithstanding the smoke holes: hence it may be concluded, that the strength of these tower bastions does by no means answer their expences; and that, if small bastions were made instead of them, without casemates, they would be much better, and less expensive.

_Traditore_, in fortification, signifies the concealed or hidden guns in a fortification, behind the reverse of the orillon.

_Traverse_, in fortification, is a parapet made across the covert way, opposite to the saliant angles of the works, and near the places of arms, to prevent enfilades; they are 18 or 20 feet thick, and as high as the ridge of the glacis. There are also traverses made in the caponniers, but then they are called _tambours_.

_Traverses_ are likewise made within other works, when there are any hills or rising grounds from whence the interior parts of these works may be observed. Traverses that are made to cover the entrances of redoubts in the field, need not be above 8 or 10 feet thick.

_Trous-de-loup_, or wolf holes, round holes made about 5 or 6 feet deep, with a stake in the middle: they are generally dug round a field redoubt, to obstruct the enemy’s approach; circular at top, and about 4¹⁄₂ feet diameter; pointed at the bottom like an inverted cone. Two or three rows of them are dug chequerwise, about 6 paces from the edge of the ditch, viz. two rows of holes exactly opposite to each other, and a third row in the middle, covering the intervals.

_Wicket_, a small door in the gate of a fortified place, at which a man on foot may go in, and which may be opened though the gate itself be kept shut.

_Works._ All the fortifications about a place, are called the _works_ of a place.

_Out-works._ All detached _works_ in a fortification are so called. See _Dehors_.

_Zig-Zag._ See SIEGE.

_The principal maxims of fortification_, are these, viz. 1. That every part of the works be seen and defended by other parts, so that an enemy cannot lodge any where without being exposed to the fire of the place.

2. A fortress should command all places round it: and therefore all the out works should be lower than the body of the place.

3. The works farthest from the centre should always be open to those that are nearer.

4. The defence of every part should always be within the reach of musquet shot, that is, from 120 to 150 fathoms, so as to be defended both by ordnance and small fire arms; for if it be only defended by cannon, the enemy may dismount them by the superiority of their’s, and then the defence will be destroyed at once; whereas, if a work is likewise defended by small arms, if the one be destroyed, the other will still subsist.

5. All the defences should be as nearly direct as possible; for it has been found by experience, that the soldiers are too apt to fire directly before them, without troubling themselves whether they do execution or not.

6. A fortification should be equally strong on all sides; otherwise the enemy will attack it in the weakest part, whereby its strength will become useless.

7. The more acute the angle at the centre is, the stronger will be the place.

8. In great places, dry ditches are preferable to those filled with water, because sallies, retreats, succors, &c. are necessary; but, in small fortresses, wet ditches, that can be drained, are the best, as standing in need of no sallies.

_Field_ FORTIFICATION is the art of constructing all kinds of temporary works in the field, such as redoubts, field forts, star forts, triangular and square forts, heads of bridges, and various sorts of lines, &c. An army intrenched, or fortified in the field, produces, in many respects, the same effect as a fortress; for it covers a country, supplies the want of numbers, stops a superior enemy, or at least obliges him to engage at a disadvantage.

The knowlege of a field engineer being founded on the principles of _fortification_, it must be allowed, that the art of fortifying is as necessary to an army in the field, as in fortified places; and though the maxims are nearly the same in both, yet the manner of applying and executing them with judgment, is very different.

A project of fortification is commonly the result of much reflexion; but in the field it is quite otherwise: no regard is to be had to the solidity of the works; every thing must be determined on the spot; the works are to be traced out directly, and regulated by the time and number of workmen, depending on no other materials than what are at hand, and having no other tools than the spade, shovel, pick-axe, and hatchet. It is therefore in the field, more than any where else that an engineer should be ready, and know how to seize all advantages at first sight, to be fertile in expedients, inexhaustible in inventions and indefatigably active.

_Quantity and quality of the materials which are required in the construction of field-fortification._

1. Every common fascine made use of in the construction of field works or fortifications, should be 10 feet long and 1 foot thick. A fascine is raised by means of 6 pickets, which are driven obliquely into the earth, so that 2 together form the shape of a cross. These pickets are tied with willows, or birch twigs. It is upon supporters or tressels of this kind, that fascines are made, which are properly fagots bound together with rods, at intervals of 1 foot each in breadth. Six men are required to complete each fascine; viz. 2 to cut the branches, 2 to gather them up, and 2 to bind the fascines. Six men may with great ease, make 12 fascines in an hour. The smaller sort of willows, or birch twigs, are best calculated for this work. The fascines are fastened to the parapet, which would otherwise crumble and fall down. A redoubt, constructed _en crémaillere_, must have fascines 8 feet long.

2. There must be 5 pickets for each fascine, and each picket must be 3 or 4 feet long, an inch and a half thick, and sharp at one end; they serve to fasten the fascines to the parapet.

3. When you cannot procure wood for the fascines, the parapet must be covered or clothed with pieces of turf, 4 inches thick, and a foot and a half square; these are fastened to the parapet with 4 small pickets 8 inches long.

4. The fraises, or pointed stakes, must be 8 feet long, 5 inches thick, and be sharp at the top. The beams upon which they are laid, must be 12 feet long and 6 inches thick. These beams are spread horizontally along the parapet, and fraises are fixed to them, with nails 7 inches long; after which the beams are covered with earth. Two men will make 12 fraises in an hour.

5. The palisades, by which the ditch or fossé of a work is fortified, must be 9 or 10 feet long, and 6 inches thick; they must, likewise, be sharpened at the end. If you cannot procure them of these dimensions, you must use smaller ones; in which case you will have the precaution to mix a few large stakes.

6. The pickets, which are fixed in _trous-de-loup_ or wolf-holes, must be 6 feet long, 4 inches thick, and sharp at the top.

7. The beams belonging to a _cheval-de-frize_ must be 12 feet long, and 6 inches broad. The spokes which are laid across, must be 7 feet long, 4 inches thick, and placed at the distance of 6 inches from each other. These _chevaux-de-frizes_ are made use of to block up the entrances into redoubts, to close passages or gates, and sometimes they serve to obstruct the fossé.

8. Gabions are constructed of various sizes. Those which are intended for field works, must be 3 or 4 feet high, and contain 2 or 3 feet in diameter. These gabions are made by means of long stakes, 3 or 4 feet long, which are placed so as to form a circle, which is 2 or 3 feet in diameter. The pickets must be covered and bound in the same manner as hurdles are. Gabions are chiefly of use in embrasures. They are fixed close to each other, and are afterwards filled with earth. There are also gabions of one foot, with 12 inches diameter at the top, and 9 at the bottom. The bank of the parapet is lined with gabions of this construction, behind which troops may be stationed, so as to fire under cover through the intervals. A quantity of large wooden mallets, rammers, hatchets, axes, and grappling irons, is required for this work.

_Names of all works used in field_ FORTIFICATION.

_Bridge heads_, or _têtes de pont_, are made of various figures and sizes, sometimes like a redan or ravelin, with or without flanks, sometimes like a horn or crown work, according to the situation of the ground, or to the importance of its defence. Their construction depends on various circumstances; for, should the river be so narrow, that the work may be flanked from the other side, a single redan is sufficient; but when the river is so broad, that the saliant angle cannot be well defended across the river, flanks must be added to the redan; but should a river be 100 toises, or more across, half a square may be made, whose diagonal is the river side; and where the river is from 3 to 500 toises broad, a horn, or crown-work should be made. All the different sorts of _heads of bridges_, are to be esteemed as good works against a sudden onset only, and their use is almost momentary, as they sometimes serve but for a few days only, and at most during a campaign.

_Dams_ are generally made of earth, but sometimes of other materials, as occasion may require: their use is to confine water.

_Flêche_ a work consisting of two faces, terminating in a saliant angle of 90°, the faces are generally 75, or 80 feet long, the parapet 6 feet thick, and the ditch 7 feet broad.

_Forts_, in field fortification, are of various sorts, viz.

_Field forts_ may be divided into two kinds: the one defending itself on all sides, as being entirely surrounded; the other, bordering on a river, &c. remain open at the gorge. They have the advantage of redoubts, in being flanked, and the disadvantage in containing less within, in proportion to their extent.

_Star forts_ are so called, because they resemble that figure. They were commonly made of 4 angles, sometimes of 5, and very rarely of 6; but we find them now made of 7 and 8 angles. Let their figure however, be what it will, their angles should be equal; if formed of equilateral triangles, so much the better; for then the flanking angle being 120°, the fires cross better and nearer; and as the 2 flanks are on the same line, the space not defended before the saliant angle, is reduced to a parallelogram, whose smallest side is equal to the gorge.

_Bastioned forts_ differ in nothing from that of places, except that the figure is less, and the attack supposed of another kind. It is reckoned sufficient to flank them with half bastions.

_Triangular forts._ As these kind of _forts_ contain less in proportion than any other, they are consequently used as seldom as possible.

_Square forts_ are in many respects preferable to the triangular ones. See FORT.

_Lines_, in field fortification, are of several sorts, viz. the front of a fortification, or any other field work, which with regard to the defence, is a collection of lines, contrived so as reciprocally to flank each other.

_Lines of intrenchment_ are made to cover an army; or a place indifferently fortified, and which sometimes contains the principal magazine of an army; or to cover a considerable extent of ground, to prevent an enemy from entering into the country to raise contributions, &c.

_Lines_, of whatever form or shape, should be every where equally strong, and alike guarded.

_Maxims._ 1st. To inclose with the work as much ground as possible, having regard to circumstances. This attention chiefly concerns redoubts and small works.

2d. If there are several works near each other, their lines of defence should be so directed, as to defend each other without being annoyed by their own fire.

3d. Not to depend on the defence of small arms, but where they can fire at right angles; as they too generally fire without aim, and directly before them.

4th. Not to have recourse to the 2d flank or fire of the curtain, but when there is an absolute necessity.

5th. That the flanking angle be always a right one, or at least obtuse, but never to exceed 100°, if possible, there being no fear here, as in a fortification, of the flank being too much exposed. Besides, it is not necessary to graze the faces, or even to fire obliquely on them; since there is no danger of being exposed to the defence of a breach, or lodgment of the miners. The only thing to apprehend, is a sudden attack.

6th. That the flanking parts be sufficiently extended, so that the interior of their parapets at least may rake the whole breadth of the opposite ditch.

7th. Never to make an advanced ditch in dry ground, unless it can be enfiladed throughout, and under a proper angle be defended by the work which it covers, or surrounds.

8th. Not to allow more than from 60 to 80 toises for the lines of defence, when they proceed from two flanks separated by two branches, forming a saliant angle, or when not made to cross, though produced.

9th. That the parts most extended, and consequently the weakest in themselves, be as much defended as possible, and have at least the fire of two flanks, besides their own direct fire.

_Redans_ are a sort of indented works, consisting of lines and faces, that form saliant and re-entering angles, flanking one another. Lines are often constructed with redans: their saliant angles are generally from 50 to 70°.

_Indented redans_ are when the two faces are indented, in that case the faces of each indented angle is 8¹⁄₂ feet only.

_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.

FORTIFICATION, according to the method of Pagan, consists in three different sorts, viz. the great, the mean, and little, whose principal dimensions are contained in the following

TABLE.

+-----------------------------------+---------------+---------------+
| The great FORTIFICATION. | The mean. | The little. |
+-------------------+-------+-------+-------+-------+-------+-------+
| | for |for all| for |for all| for |for all|
| |squares| other |squares| other |squares| other |
| | | poly- | | poly- | | poly- |
| | | gons | | gons | | gons |
+-------------------+-------+-------+-------+-------+-------+-------+
|Exterior side | 200 | 200 | 180 | 180 | 160 | 160 |
+-------------------+-------+-------+-------+-------+-------+-------+
|The perpendicular | ?7 | 30 | 24 | 30 | 21 | 3? |
+-------------------+-------+-------+-------+-------+-------+-------+
|The face | 60 | 60 | 55 | 55 | 45 | 50 |
+-------------------+-------+-------+-------+-------+-------+-------+
|The flank | 22 | 24 2| 19 1| 24 | 18 3| 23 2|
+-------------------+-------+-------+-------+-------+-------+-------+
|The curtain | 73 2| 70 5| 63 4| 60 4| 63 5| 50 4|
+-------------------+-------+-------+-------+-------+-------+-------+
|The line of defence| 141 4| 141 2| 126 1| 126 5| 115 5| 112 3|
+-------------------+-------+-------+-------+-------+-------+-------+

Blondel fortifies within the given polygon: he establishes two sorts of fortification; the great one, whose exterior side is 200 toises, and the lesser one 170; because he will not have the line of defence exceed 140 toises, which is the greatest musquet shot, nor less than 120 toises, not to increase the number of bastions. He begins by the diminishing angle, which may be found by taking 90 degrees from the angle of the polygon, and by adding 15 degrees to the third of the remainder.

Vauban’s method is divided into little, mean, and great: the little is chiefly used in the construction of citadels; the mean, in that of all sorts of towns; and the great, in particular cases only.

TABLE.

+-----------------------+--------------------------++
| | Forts. ||
+-----------------------+---+---+------+---+---+---++
|Side of Polygon | 80| 90|100 |110|120|130||
+-----------------------+---+---+------+---+---+---++
|Length of perpendicular| 10| 11| 12¹⁄₂| 14| 15| 16||
+-----------------------+---+---+------+---+---+---++
|Faces of Bastions | 22| 25| 28 | 30| 33| 35||
+-----------------------+---+---+------+---+---+---++
|Capital of Ravelins | 25| 28| 30 | 35| 38| 40||
+-----------------------+---+---+------+---+---+---++

+-----------------------++---------------++-------+-------+
| || Little. || Mean. | Great.|
+-----------------------++---+---+---+---++---+---+---+---+
|Side of Polygon ||140|150|160|170||180|190|200|260|
+-----------------------++---+---+---+---++---+---+---+---+
|Length of perpendicular|| 20| 21| 23| 25|| 30| 31| 25| 22|
+-----------------------++---+---+---+---++---+---+---+---+
|Faces of Bastions || 40| 42| 45| 47|| 50| 53| 55| 60|
+-----------------------++---+---+---+---++---+---+---+---+
|Capital of Ravelins || 45| 50| 50| 52|| 55| 55| 60| 50|
+-----------------------++---+---+---+---++---+---+---+---+

In the first horizontal row are the numbers expressing the lengths of the exterior sides from 80 to 260.

In the second, the perpendiculars answering to these sides.

In the third, the lengths of the faces of the bastions; and in the fourth, the lengths of the capitals of the ravelins.

Belidor’s method is divided also into little, mean, and great: and in all three the exterior side is 200 toises; the perpendicular of the little is 50, that of the mean 55, and the great 40: the faces of the first 70, the second 70, and the third 55 toises.

Scheiter’s method is divided into the great, mean, and small sort. The exterior side of the polygon for the great sort is 200 toises, the mean sort 180, and the small 160. The line of defence in the first is 140 toises, the second 130, and the third 120. This line is always rasant. All the other lines are fixed at the same length for all polygons, whose structure chiefly depends upon the knowlege of the exterior side, of the capital, or of the flanked angle, the rest being easily finished.--See the TABLE.

TABLE _of capitals and flanked Angles_.

+---------------------------+------+-----+-----+-----+-----+
| Polygons. | IV | V | VI | VII | VIII|
+---------------------------+------+-----+-----+-----+-----+
|The flanked angles in the | deg. | | | | |
|3 sorts of fortification. | 64 | 76 | 84 | 90 | 95 |
+---------------------------+------+-----+-----+-----+-----+
| |toises| | | | |
|Capital for the great sort.| 46 | 49 | 51 | 52 | 53 |
+---------------------------+------+-----+-----+-----+-----+
|Capital for the mean sort. | 42 |44¹⁄₂|46¹⁄₂|48¹⁄₂| 50 |
+---------------------------+------+-----+-----+-----+-----+
|Capital for the small sort.| 39 |41¹⁄₂|42¹⁄₂| 45 | 46 |
+---------------------------+------+-----+-----+-----+-----+

+---------------------------+-----+-----+-----+-----+
| Polygons. | IX | X | XI | XII |
+---------------------------+-----+-----+-----+-----+
|The flanked angles in the | | | | |
|3 sorts of fortification. | 97 | 99 | 101 | 103 |
+---------------------------+-----+-----+-----+-----+
| | | | | |
|Capital for the great sort.|54¹⁄₂|56¹⁄₂| 58 | 59 |
+---------------------------+-----+-----+-----+-----+
|Capital for the mean sort. | 51 |52¹⁄₂| 54 | 54 |
+---------------------------+-----+-----+-----+-----+
|Capital for the small sort.|47¹⁄₂|48¹⁄₂| 50 |50¹⁄₂|
+---------------------------+-----+-----+-----+-----+

Errard, of Bois le-Duc, who was employed by Henry IV. and was the first that laid down rules in France respecting the best method of fortifying a place so as to cover its flank, constructs that flank perpendicular to the face of the bastion; but by endeavoring to cover it effectually, he makes the gorges too exiguous, the embrasures too oblique, and leaves the ditch almost defenceless.

The Chevalier de Ville, who succeeded Errard, draws the flank line perpendicular to the curtain; but here again the embrasures are too oblique, especially in the polygons, and the ditch is necessarily ill guarded. This engineer’s method of fortifying is stiled by most authors, the _French method_. His favorite maxim is to make the flank angle straight, and the flank equal to the demigorge.

Count Pagan makes the flank perpendicular to the line of defence, which method seems to agree perfectly with this maxim, because by that means the flank so raised covers as much as possible the face of the opposite bastion; but notwithstanding this apparent advantage the flank becomes too small and is too much exposed to the enemy’s batteries. This engineer acquired great reputation during the several sieges which he assisted in conducting under Louis XIII. His system has been improved upon by _Alain Marrison Mallet_, and his construction in fortification is to this day esteemed the most perfect. It differs very little from Marshal Vauban’s first system. Count Pagan has pointed out the method of building casemates in a manner peculiar to himself.

Marshal Vauban has judiciously steered between these different methods. He has drawn his flank in such a manner, that it does not stand too much exposed, nor does its collateral line of defence extend too far from the direct line of defence. He has effected this by lengthening out his flank and giving it a circular form.

It cannot be disputed but that large and extensive flanks and demi-gorges are superior to narrow and confined ones. The more capacious the flank is, the better calculated will it prove for the disposition of a formidable train of artillery. From this conviction many writers in their proposed systems of fortification, have added a second flank, in order to augment the line of defence; but they did not foresee, that this second flank is not only incapable of covering the face of the opposed bastion, except in a very oblique and insecure direction, but that the right flank, or the flank of the bastion, is thereby more exposed to the enemy’s batteries, which, it must be acknowleged, is a great fault.

The prevailing system of the present day is to make the flanks of the bastion as wide as possible, without having recourse to a second flank, unless it be absolutely necessary. Those gorges are likewise best which are most capacious, because they afford space and ground in the bastion for the construction of intrenchments within, should the enemy have effected a practicable breach.

All parts of a fortification which stand exposed to the immediate attacks of a besieging enemy, must be strong enough to bear the boldest attempts, and the most vigorous impressions. This is a self-evident maxim, because it must be manifest to the most common understanding, that works are erected round a place for the specific purpose of preventing an enemy from getting possession of it. It consequently follows, that flanked angles are extremely defective when they are too acute, since their points may be easily flanked and destroyed by the besieger’s cannon.

The Dutch construct at sixty degrees; but according to Vauban’s method, no work should be under seventy-five degrees, unless circumstances and situation should particularly require it.

A place to be in a state of defence, should be equally strong in all its relative directions; for the enemy would of course make the weak part his object of attack, and finally succeed in getting possession of the town. The body of the place must have a command towards the country, and no quarter in the outward vicinity of it must overlook, or command either the place itself, or its outworks. Those works which are nearest to the centre of the place, must have a greater elevation than the more distant ones.

The first regular system of fortification which appeared and was adopted in France, owed its origin to Errard of Bois-le-Duc, whom we have just mentioned. His method, however, has been uniformly rejected by able engineers; and if we may give credit to the report of Ozanan, Errard himself never carried his own system into practice.

Next to Errard of Bois-le-Duc, came the Chevalier Antoine de Ville, who was engineer under Louis XIII. and published an excellent treatise upon fortification. His method is stiled by most authors, the _French method_. Others call it the _Compound System_, or _Systeme à trait Composé_, because it united the Italian and Spanish methods. He was, indeed, by no means an advocate for new systems; for he generally observed, that any new method, or invention was extremely easy, so long as it was confined to the mere alteration of something in the measure, or in the disposition of those parts of fortification which have been discussed by other authors.

The Count de Pagan followed after, and had the good fortune to propose a system which entirely superseded the other two. We have already mentioned the principal feature, in his method.

Marshal Vauban, whose reputation rose upon the manifest superiority which his skill gave him over all others that had written upon fortification, likewise proposed three methods, with considerable improvements: _viz._ The _great_, the _mean_, and the _little_.

The great method, according to Vauban, contains on its exterior side from 200 to 230, or 240 toises. This extent is not uniformly the same throughout all the sides of a place, but is confined to that side which lies along the banks of a river, where he uniformly erects considerable outworks.

Vauban made use of his second method in fortifying Béfort and Landau. On account of the bad local situation of Béfort, and the impossibility of fortifying it with common bastions that would not be exposed to an enfilade in almost every direction, in spite of the traverses or _rechutes_ which might be made: he invented arched bastions that were bomb proof, which he called _tours bastionnées_, or _towers with bastions_. These arched bastions are covered by counter-guards, the height of whose parapet almost equals the elevation of the towers themselves. Although strictly speaking, both these places are irregularly fortified, nevertheless a method of regular defence may be established from the construction of their works.

Vauban’s third system grows out of the second, and for that reason it is called _ordre renforcé_, the _reinforced order or method_. It was adopted in the fortifications of New Brisac. Vauban left nothing untried to bring this system to perfection, and he had the ingenuity to execute his plan at a less expence, than it would otherwise have been effected, by means of half revetements which he threw up in the outward works called the dehors.

This system, however, (ingenious and unrivalled as it certainly is,) has not escaped the censure of some writers. It must nevertheless be acknowleged, that their remarks are either founded in envy, or that they proceed from ignorance.

There are other systems of fortification which have been proposed by the writers of other countries besides France. We shall give a brief detail of them, and leave the inquisitive to go more at length into the nature of their methods, by referring them to the different treatises.

The Italians have furnished several authors who have written variously on the subject of fortification. The method proposed by Sardis has been generally esteemed the best.

The Spaniards in their methods of fortifying, never adopt that which adds a second flank. The obtuse flanked angle is not looked upon by their best engineers as a defective system in fortification.

Both the Italians and the Spaniards speak frequently of the _ordre renforcé_, which was originally invented to lessen the number of bastions in a great town or fortified place, and to render consequently the line of defence equal to the range of musquetry.

The Chevalier St. Julien, a very able engineer, has published a method, by which, he asserts, that works may be constructed not only at a less expence than others require, but in a manner that must render his defence or attack more formidable. He has likewise invented a new method for the defence of small places, which is preferable to the first, although it is not without faults. According to his system, the reach of the musquet is taken from the centre of the curtain. To this end he directs, that a covert lodgment, 7 feet high, and 10 toises wide, be constructed from that spot to the gorge of the half moon or ravelin. Cannon is disposed along the faces, and a gallery is erected for the musquetry, which likewise serves as a passage to the ravelin.

Francis Marchi, a gentleman of Bologna, in his folio edition, has furnished us with upwards of 160 different methods of constructing fortifications.

The Dutch uniformly pursue the system published by Marollois.

Bombelle has likewise established three sorts of fortification, the great royal, _grand royal_; the mean; and the little royal, _petit royal_. His method agrees with the sound maxims of good fortification much more than any of the preceding ones.

Blondel has published a system of fortification, which he divides into two principal heads; the _great_, whose exterior side contains 200 toises; and the _little_, where the side does not exceed 170 toises. His reason is, because he objects to the line of defence having more than 140 toises, which is the furthest reach of musquetry, or less than 120 toises, to prevent an unnecessary increase of bastions. The principles of Blondel’s system resemble, in a great degree, those upon which Pagan’s is founded, and chiefly consist in methods of fortifying inward posts. The invention has certainly great merit, but its adoption must prove expensive in all its practical branches. It must, moreover, be manifest, that the four long batteries which are supported by flanks of his construction, must serve as so many scaling ladders, or steps to the besiegers, the instant they have effected a breach by cannon shot, or shells.

In 1689, a work was published, entitled:

_Nouvelle maniere de fortifier les places, tirée de methodes du Chevalier de Ville, du Comte de Pagan, et de M. de Vauban; avec des remarques sur l’ordre renforcé, sur les desseins du Capitaine Marchy, et sur ceux de M. Blondel._ This work is full of strong reasoning, from the result of which the author has formed a new method, containing indeed, nothing original, but giving references to what has already appeared, and disposing the different parts in so judicious a manner, as to shew how a place may be rendered stronger, and be subject at the same time to a less expence. This writer divides fortification into three parts, the great, the mean, and the little.

There is a second and a third method proposed anonymously, and containing mere simple designs. That method in which a modern author gives it the preference over the system of New Brisac, contains little useful information, and contributes less to the real art of fortifying places.

Donato Rosetti, a Canon belonging to Livournia, professor of mathematics in the academy at Piedmont, and mathematician to the Duke of Savoy, has written upon a method of constructing works in what he calls _fortification à rebours_, or fortification in reverse; so called not only because the re-entering angle of the counterscarp is opposite to the flanked angle; but because, in his idea, it will be necessary to attack it from the reverse side of other works. His system is very simple, and does not require a sacrifice of much money, or stand in need of many men to defend the works: although he can, on his side, pour as much fire upon the enemy, as could be furnished by more complicated methods.

Antonio de Herbart, major of artillery, in the Duke of Wurtemberg’s service, in 1735, published a treatise on fortifications with square angles, which he calls _angular polygons_.

Monsieur de Montalembert has lately endeavored to bring arches, which are so much condemned by the Chevalier de Ville, into repute. He treats the subject in a manner, and upon principles so similar to those proposed by Antonio de Herbart, that it is almost impossible to separate the two systems. M. de Montalembert asserts, that the science of fortification, (as it is established and taught at present) can only be valued by the public on account of its illusion. He looks upon the use of bastions, as the effect of prejudice; he rejects them wholly, and substitutes in their room, a front of _angular tenailles, polygons with small wings, and angular polygons_. The engineers of the present day assert with confidence, that the chief security to be derived in works that are supported by bastions, must depend upon cross and reverse firing directed against the enemy’s lodgments on the glacis. Large half-moons are made, not only for the purpose of covering the curtains and the flanks of bastions, but principally to obtain a reverse firing, which effectually prevents the enemy from maintaining his ground on the glacis of a bastion, before he has taken the two collateral half-moons.