in the first vertical column are the numbers saliant angle; as likewise all ditches are in expressing the lengths of the exterior sides from general. cighty to 260. In the second, the perpendiculars When the ravelins are made with flanks, as in answering to these sides. In the third, the plate I. fig. 3, the faces should terminate on those lengths of the faces of bastions; and in the of the bastions, at least five toises from the fourth, the lengths of the capitals of the ravelins. shoulders. The flanks are made by setting off The forts are mostly, if not always, squares : ten toises from the extremities of the faces, from for which reason, the perpendiculars are made f to h, and from m to l; and from the points one-eighth of the exterior sides ; because, if they h, 1, the flanks h k,l p, are drawn parallel to the were more, the gorges of the bastions would be capital LO of the ravelin. come too narrow. There are sometimes redoubts made in the raIn the little fortification or citadels, chiefly velin, such as in fig. 2, which is done by setting pentagons, the perpendiculars are made one- off sixteen toises from the extremities of the faces seventh of the exterior side. In mean fortifica- on the semi-gorges from N to h, and from M to tion, from any number of sides to an hexagon up- a; and from the points b, a, the faces are drawn wards is used; and the great is seldom used but parallel to those of the ravelin; the ditch before in an irregular fortification, where there are some the redoubts is six toises, and its counterscarp sides that cannot be made less without much ex- parallel to the faces. pense; or in a town which lies near a great Of Tenailles.-A tenaille is a work made in the river, where the side next the river is made from ditch before the curtains; the parapet is only 200 to 260 toises; and, as that side is less ex- two or three feet higher than the level ground of posed to be attacked than any other, the per- the ravelin. There are three different sorts; the pendicular is made shorter, which saves much first are those, as in fig. 4, which are made in the expense. direction of the lines of defence, leaving a pasThe faces of the bastions are all two-sevenths of sage of five toises between their extremities and the exterior sides, or nearly so, because the frac- the flanks of the bastions, as likewise another of two in the middle for a bridge of communication In general, in all squares, the perpendicular to the ravelin. is one-eighth of the exterior side, and all penta- The second sort are as those in fig. 5. Their gons one-seventh, and in all the rest upwards faces are in the lines of defence, and sixteen of one-sixth. toises long, besides the passage of three toises Of the Construction of Orillons and retired between them and the flanks of the hastion ; Flanks. Describe the front MPQRST as be- their flanks are found by describing arcs from fore, and divide the flank into three equal parts, one shoulder of the tenaille as centre through the of which suppose Sr to be one; from the op- other, or on which are set ten toises for the flanks posite flanked angle M draw a line Mr, in desired. which take the part mr of five toises ; take like The third sort are those as in fig. 6. Their wise Rn in the line of defence MR, produced faces are sixteen toises, as in the second sort, equal to five toises, and join nm, upon which as and the flanks are parallel to those of the basa base describe the equilateral triangle npm, tions. and from the angle p, opposite to the base as The use of tenailles, in general, is to defend centre, is described the circular flank nm. And the bottom of the ditch by a grazing fire, as likeif Sr be bisected by the perpendicular 1, 2, and wise the level ground of the ravelin, and espeanother be erected upon the face ST, at S, cially the ditch before the redoubt within the the intersection 2 of these two perpendiculars ravelin, which can be defended from no where will be the centre of the arc which forms the else so well as from them. orillon. The first sort do not defend the ditch so well The orillons are very useful in covering the as the others, as being too oblique a defence; retired flanks, which cannot be seen but directly but, as they are not subject to be enfiladed, M. in the front; and, as these orillons are round, Vauban generally preferred them in the fortifythey cannot be so easily destroyed as they would ing of places, as in the citadel of Lille, at Lanbe if they were of any other figure. dau, New Brisac, and in many other places. Of the Construction of Ravelins or Half-moons. The second sort defend the ditch much better Fig. 2. Set off fifty-five toises, from the re-enter- than the first, and add a low flank to those of the ing angle ( of the counterscarp, on the capital bastions; but, as these flanks are liable to be enOL, or on the perpendicular produced ; and filaded, they have not been much put in practice. from the point L draw lines to the shoulder A B; This defect might however be remedied, by mawhose parts L M, LN, terminated by the coun- king them so as to be covered by the extremities terscarp, will be the faces, and MO, ON, the of the parapets of the opposite ravelins, or by semi-gorges of the ravelin required. This is Mr. some other work. Vauban's method of constructing ravelins, ac- As to the third sort, they have the same adcording to some authors: others say the faces of vantage as the second, and are likewise liable the ravelin should terminate on those of the bas- to the same objections; for which reason they tions within three toises of the shoulders; which may be used with the same precautions which seems to be the best way, for these ravelins have been mentioned in the second. cover the flanks much better than the others. Tenailles are esteemed so necessary, that there The ditch before the rarelin is twelve toises, is hardly any place fortified without them; and its counterscarp parallel to the faces of the rave- with reason: for, when the ditch is dry, the part lins, and is made in a circular arc, before the behind the tenailles serves as a place of arms from which the troops may sally, and destroy the Of Counterguards.-Fig. 10, 11. When the works of the enemy and the ditch, oppose their counterguard is placed before the ravelin, set oft descent, and retire with 'safety; and the com- forty toises on the capital of the ravelin from the munication from the body of the place to the saliant angle A to the saliant angle B, of the ravelin becomes easy and secure, which is a great counterguard; and ten from C to D, on the advantage; for by that means the ravelin may counterscarp of the ditch. be a much better defence, as it can be supplied When the counterguard is before the bastion, with troops and necessaries at any time. And, such as in fig. 2, its saliant angle F is fifty toises if the ditch is wet, they serve as harbours for from the saliant angle E of the bastion, and the boats, which may carry out armed men to op- breadth near the ditch of the ravelin ten toises as pose the passage over the ditch whenever they before. please; and the communication from the tenailles The ditch before the counterguards is twelve to the ravelin becomes likewise much easier than toises, and its counterscarp parallel to the faces. it would be without them. Counterguards are made before the ravelin on Of Lunettes.-Fig. 7, plate I. Lunettes are some particular occasions only; but are freplaced on both sides of the ravelin, such as B, to quently constructed hefore the bastions, as coincrease the strength of a place : they are con- vering the flanks wonderfully well. Some austructed by bisecting the faces of the ravelin with thors, as Mr. Blondel and Mr. Coehorn, will the perpendicular LN; on which is set off thirty have them much narrower than they are here. toises froin the counterscarp of the ditch, for one Of Horn-works.-Fig. 12, plate I. Produce of its faces; the other face, PN, is found by the capital of the ravelin beyond the saliant making the semi-gorge, TP, of twenty-five angle A, at a distance A B of about eighty toises toises; the ditch before the lunettes is twelve draw DBE at right angles to AB; in which toises, the parapet three, and the rampart eight, take BD, BE, each equal to fifty-five toises ; as in the ravelin. and on the exterior side, D E, trace a front of a There is sometimes anotner work made to co- polygon in the same manner as that of the body ver the saliant angle of the ravelin, such as A, of the place, making the perpendicular B F ten called the bonnet, whose faces are parallel to toises, and the faces thirty. those of the ravelin, and when produced bisect The branches Da, Eb, of the horn-work, when those of the lunettes; the ditch before is ten produced, terminate on the faces of the bastions, toises. ** within five toises of the shoulders. The ditch of There are likewise lunettes, such as D in fig. the horn-work is twelve toises, and its counter8, whose faces are drawn perpendicular to those scarp parallel to the branches, and in the front of the ravelin, within a third part from the saliant terminates at the shoulders, in the same manner angle; and their semi-gorges are only twenty as the great ditch before the bastions. toises. The capital of the ravelin before the front of These kinds of works may make a good de- the horn-work is thirty-five toises, and the faces fence, at no very great cost; for, as they are so terminate on the shoulders, or rather two or near the ravelin, the communication with it is three toises beyond them: and the ditch before very easy, and one cannot well be maintained the ravelin is eight toises. till they are all three taken. Retrenchments are sometimes made within Of Tenaillons.-Fig. 9, plate I. Produce the the horn-works, such as S, S; which are confaces of the ravelin beyond the counterscarp of structed by erecting perpendiculars to the faces the ditch, at a distance M N of thirty toises, and of the ravelins, within twenty-five toises of their take on the counterscarp of the great ditch fif- extremities. This retrenchment, like all others, teen toises from the re-entering angle p to 9, and has a parapet turfed only with a berm of eight draw Ng; then q N M p will be the tenailles re- feet before it; as likewise a ditch from three to quired; its ditch is twelve toises, that is, the five toises broad. sarne as that of the ravelin. Sometimes a retired Fig. 13. When a horn-work is made before battery is made in the front of the tenaillons, as the bastion, the distance D L of the front from in B; this battery is ten toises from the front the saliant angle of the bastion is 100 toises, to which it is parallel, and fifteen toises long. and the branches terininate on the faces of the Retrenchments are commonly made in the adjacent ravelins within five toises from their tenaillons, such as 0; their parapets are paral- extremities; all the rest is the same as before. lel to the fronts M N, and bisect the side qN; Of Crown-works.- From the saliant angle, A, the ditch before the retrenchment is three toises; fig. 1, plate II. of the ravelin, as a centre, deand there is a banquette before the parapet next scribe an arc of a circle with a radius of about to the ditch of about eight feet, called berm; 120 toises, cutting the capital of the ravelin prowhich serves to prevent the earth of the parapet duced at C; from the point C, set off the cords which seldom has any revetment from falling into CB, C F, each of them equal to 110 toises; and the ditch. on each of which, as an exterior side, construct The ravelin, before which tenaillons are con- a front of polygon of the same dimensions as in structed, must have its saliant angle much the horn-work; that is, the perpendicular should greater than the former construction makes them; be eighteen toises, the faces' thirty, and the otherwise the saliant angles of the tenaillons branches terminate on the faces of the bastions become too acute; for which reason we made within lwenty-five toises of the shoulders. the capital of this ravelin forty-five toises, and The ditch is twelve toises, the capital of the the faces terminate within three toises of the ravelins thirty-five, and its ditch eight; that is, shoulders. the same as in the born-work. Sonetimes the crown-work is made before the like a ravelin, with flanks placed beyond the bastions, as in fig. 2. The arc is described from glacis, such as B; they are made to occupy some the saliant angle A of the bastion, with a radius spot of ground which might be advantageous to of 120 toises as before ; and the branches ter- the besiegers; likewise to oblige the enemy to minate on the faces of the adjacent ravelins within open their trenches farther off than they would twenty-five toises of their extremities: the rest do otherwise. The distance from the covert-way of the dimensions and constructions are the same ought not to exceed 120 toises, that it may be as before. defended by musket-shot from thence. Horn-works, as well as crown-works, are The gorge, a b, is forty toises; the flanks, ac, never made but when a large spot of ground falls bf, which are perpendicular to the gorge, ten; beyond the fortification, which might be advan- and the faces cd, f'd, thirty : the ditch before it tageous to an enemy in a siege, or to cover some is six toises, ending in slopes at both ends; the gate or entrance into a town. covert-way four; the branches of the covert. Of Covert-ways and Glacis.—These are es- way are forty-two toises long, or thereabouts; teemed some of the most essential parts of a the faces of the places of arms y, y, which are modern fortification ; and it is certain the taking perpendicular to the branches, ten; and the other, the covert-way, when it is in good condition and which is parallel to them, fourteen. well defended, is generally the most bloody ac- The communication from the covert-way into tion of the siege. After having constructed the the redoubt, is five or six toises wide: a traverse body of the place, and all the outworks which is made just at the entrance, and another in the are thought necessary, lines are drawn parallel middle when it is pretty long. The parapets to the utmost counterscarp of the ditches, at six of this communication terminate in a slope or toises distant from it; and the space mn, mn, glacis. included between that line and the counterscarp, If these redoubts are above fifty toises distant will be the covert-way required. from the covert-way, the besiegers carry their Fig. 3. There is in every re-entering angle trenches round, and enter through the gorge; of the counterscarp a place of arms, m; which by which means the troops that are in them are is found by setting off twenty toises from the re made prisoners of war, if they do not retire entering and angle a, on both sides from a to b, betimes; to prevent which some other outworks and from a to c: and from the points b c, as should be made to support them. centres, arcs are described with a radius of Of Second Ditches und Covert-ways.- Plate II. twenty-five toises, so as to intersect each other in fig. 4. When the ground is low, and water to d; then the lines drawn from this intersection be found, there is often a ditch about ten or twelve to the point b, c, will be the faces of the places toises made round the glacis; and opposite to of arms. the places of arms are constructed lunettes, be If lines are drawn parallel to the lines which yond the ditch : such as D, whose breadth on terminate the covert-way, and the places of arms, the counterscarp of the ditch is ten toises, from it twenty toises distant from them, the space a, b to a, and from c to d; and the faces a L, I, f, x, between these lines and those which termi- are parallel to those of the places of arms; the nate the covert-way, will be the glacis. ditch before them is from eight to ten toises At the extremities of the places of arms are wide. traverses made, such as v, v, wbich serve to en- The second covert-way is fuur toises, the semiclose them; these traverses are three toises thick, gorges of the places of arms, m, about fifteeen, and as long as the covert-way is broad, and a and the faces perpendicular to the counterscrap; passage is cut in the glacis round them, of about the second glacis is from fifteen to eighteen toises six or eight feet, in order to have a free commu- broad. This second covert-way has traverses nication with the rest of the covert-way every where in the same manner as the first. There are also traverses of the same dimensions Of Profiles.--A profile is the representation before every saliant angle of the bastion and out- of a vertical section of a work; it serves to show works, and are in the same direction as the faces those dimensions which cannot be represented of those works produced ; and the thickness lies in plans, and is necessary in the building of a at the same side as the parapets. fortification. Profiles are generally constructed The passages round these last traverses are upon thirty feet to an inch. It would be endless likewise from six to eight feet wide. to describe all their particular dimensions; we In each place of arms are two sally ports, 2,, shall, therefore, lay down the principal rules which are ten or twelve feet wide, for the troops only, given by M. Vauban, on this subject. to sally out: in time of a siege they are shut up, 1. Every work ought to be at least six feet with barriers of gates. higher than that before it, so that it may conOf Arrows and Detached Redoubts.-An arrow mand those before it; that is, that the garrison is a work made before the saliant angles of the may fire from all the works at the same time, glacis, such as A, fig. 3. It is composed of a with great and small arms, at the besiegers in parapet of three toises thick, and forty long; and their aproaches. Several authors, however, obthe ditch before it five toises, terminating in a ject against it. For, say they, if you can discover slope at both ends. The communication from the enemy from all the works, they can discover, the covert-way into these arrows is four or five by the same reason, all the works from their toises wide; and there is a traverse, r, at the batteries; so that they may destroy them withentrance, of three toises thick, with a passage of out being obliged to change their situation, and six or eight feet round it. thereby dismount all the guns of the place before A detached redoubt is a kind of work much they come near it. But, if all the works were of the same height, those within cannot be destroyed Sect II. OF THE SECOND AND THIRD SYSTEMS till such time as those before them are taken: OF M. VAUBAN. guns might be placed in the covert-way and outworks to obstruct the enemy's approach; and, M. Vauban's Second and Third Systems were when they come near the place, they might be chiefly designed, as we have stated, to protect the transported into the inner works; and, as the besieged from the ricochet fire of his own invenbody of the place would be much lower, the ex- tion, and to improve the near defence. To acpense would be considerably diminished. It complish these and some minor purposes, he should not, however, be forgotten that, when composed the body of the plan of works which works are low, they are easily enfiladed by the resemble small bastions, and are called towerricochet batteries, though this might be partly bastions. His second method is thus exemplified. prevented by making the parapets near the He begins his construction inwards, and fortifies saliant angles, for the space of eight toises on outwards, which is found a very convenient plan each side, five or six feet higher than the rest of for improving a place. the works. Let AB, Plate III, fig. 2, be the interior side 2. The covert-way should be lower than the of an hexagon of 120 toises, some authors will level ground, otherwise the body of the place have it 130, and say that they are so at Landau; must be raised very high, especially where there draw AC, BD, from the centre through the exare several outworks: this is to be understood tremities of the sides; set off six toises from A only when the works exceed each other in height, to b, and from B to c; through the points b and otherwise it need not be below the level. c, draw lines at right angles to AB, from the 3. The bases of all inward slopes of earth point b set off six toises to f outwards, and four should be at least equal to the height, if not from b to d inwards; and from the points f,d, more. draw perpendiculars f r, d n, to the capital AC; 4. The bases of all outward slopes of earth, then, if r E is made equal to rf, the point E will two-thirds of their heights. be the saliant angle of the tower bastion; and E 5. The slopes of all walls or revetments should f d n half that tower. be one-fifth of their height; or one-sixth might, If in the capitals there be taken from the saliperhaps, be sufficient; the height of a wall is ant angles of the tower-bastions, the distances estimated from the bottom of the ditch, and not EC, FD, each of forty toises, the points C and from the beginning of its foundation. D will be the saliant angles of the counterguards 6. The slopes of all parapets and traverses before the towers; from the points C and D are one-sixth of their breadth; that is, three feet draw the lines of defence Cc, Db, to the points towards the field, or the inside, where the ban- where the flanks of the towers cut the curquettes should be three feet higher than the out- tain; and which set off fifty-six toises for the side. faces of the counterguards; the flanks are found 7. When the revetment of a rampart goes as in the first method, and likewise the tenailles. qu.te up to the top, four feet of the upper part The ditch before the saliant angles of the towers is a vertical wall of three feet thick, with a square is six toises, and its counterscarp drawn to the stone at the top of it projecting six inches; and extremities of the flanks of the counterguards; a circular one below, or where the slope begins, the right line which joins the ends of these flanks of eight or ten inches diameter; they go quite wilı determine the inside of the tenailles. round the rampart, and the circular projection The ditch before the counterguards is twelve is called the cordon. Where the straight part toises at the saliant angles, and the counterscarp of the wall ends, and the slope begins, the wall is drawn to the opposite shoulders in the same is always made five feet thick; and the counter- manner as in the first method. forts or buttresses reach no higher than that place. The capital of the ravelin is forty-five toises ; 8. When the rampart is partly walled and its faces, when produced, terminate on those of partly turfed, then one-fifth of the height which the counterguards, within ten toises of the shoulis turfed must be added to five feet, to get the ders; ten toises are cut off from the faces by thickness of the wall above. And, having the the flanks which are parallel to the capital as thickness of any wall above, by adding one-fifth usual. of its height from the bottom of the ditch, the The ditch before the ravelin is ten toises, the sum will be the thickness of the wall at the covert-way five, the semi-gorges of the places bottom; but, if a sixth part is only taken for the of arms twelve, the faces seventeen, and the slope, then a sixth part must be added.. glacis twenty. For instance, suppose a rampart of thirty feet The following is the construction of M. Vauhigh from the bottom of the ditch, and that ten ban's third method, according to his plan of of these are to be turfed, then the fifth part of ten, New-Brisach. This method is applied to an ocwhich is two, added to five, gives seven for the tagon, whose exterior side, A B fig. 3, is 180 toises; wall above; and as this wall is twenty feet high, the perpendicular CD thirty; the faces AK, the fifth of which is added four, and four to the BL, of the counterguards sixty; the flanks LN, thickness seven above, gives eleven for the thickKM, are found by setting off twenty-two toises, ness near the foundation. Plate III. fig. i, as chords to the arcs described from the opposite represents, in military perspective, the profiles shoulders as centres; from the extremities of the of the body of a place, the ravelin and covert- flanks a line is drawn, which will be parallel to way: which gives a clear idea of what is meant the exterior side AB, meeting the capitals AF, by a profile, and from which those of all other BF, of the counterguards at G and H; this works may be easily conceived. line terminates the inside of the tenaille, as likewise the saliant angles G,H, of the tower- likewise disposed the covert-ways and dry ditches bastions. in such a manner that the besieger, not being able If EF be drawn parallel to GH, and at nine to dig the ground deeper than about one foot withtoises distant from it, the intersections E, F, with out finding water, may be obliged to convey to the capitals of the counterguards, will be the the spot the requisite materials for his lodgments centres of the towers; from which set off seven and the passage of the ditches in question. But toises from E to a for the semi-gorges, and draw this disposition, as well as the combined use that the flanks bc through the extremities of these Coehorn makes of wet and dry ditches, and which semi-gorges perpendicular to the line EF; these forms an essential part of his systems, evidently flanks are four toises inwards from a to c, and requires that the fortifications should be erected five outwards from a to b; the faces b G are in aquatic ground, as he supposes them to be. drawn from the point b to the point G, and the We shall therefore only advert to their principal lines joining the inside of the flanks at the end of and more general features. four toises will complete the towers. In his first system, Coehorn supposes the The ditch is six toises before the saliant angle polygon to be a regular hexagon, and that the of the towers, and its counterscarp meets the line surface of the water is but four feet lower than GH, within ten toises of the extremities M, N, of the ground. the flanks of the counterguards. Let therefore the interior side, AB plate IV. If from the point n, where the line EF inter- fig. 1, of an hexagon be 150 toises, take ÅC, BD, sects the perpendicular CD produced, you set each equal to thirty-nine, and the capitals AE, off five toises to the point r, and the lines of de- BF, each of eighty; and AG, BH, of forty; fence are drawn from the extremities of the semi- from the points E, F, draw. the lines of defence gorges a of the towers through this point r: through the points D,C; and through the points then the flanks of the counterguards produced G, H, lines parallel to ED, FC; in which take will determine the little flanks p, q, of the inside GI, HK, each equal to forty toises, for the rampart, and the extremities of these little flanks, length of the higher faces of the bastions. being joined, will give the curtain between them. To determine the lower faces EM, FN, draw The great ditch before the counterguards is 10 perpendicular to IG, equal to four toises; fifteen toises, and its counterscarp parallel to the or parallel to IG, likewise equal to four; then faces; the capital of the ravelin is fifty-five toises, r M perpendicular to EM will determine the and that of the redoubt within it twenty-three; lower face EM. the faces of the ravelin are drawn to the faces of In order to determine the tower 3, see fig. 2, the counterguards within fifteen toises from the in r M, take rs of five toises; draw Sm parallel shoulders, and those of the redoubt parallel to to E M, and equal to fourteen ; in Or produced these: twelve toises are cut off from the faces of take likewise rn equal to four, and in EM, MV, the ravelin, and six from those of the redoubt, by to eight; then if the points n, m, are joined by a the flanks which are parallel to the capital; the right line, and m, V, by an arc of sixty degrees ditch before the ravelin is twelve toises, and that you will have the outline of the tower, before the redoubt six; the covert-way and glacis The lines I 0, and Or, express two walls, the are the same as in the second method. It must first has two embrasures, and the second three; be observed, that the parapets of the counter- by which the author intended to defend the dry guards, on both sides of the saliant angles, are ditch, and the approach to the tower. raised four feet higher, for the space of twenty If from the points C, D, fig. 1, there be set off feet, above the rest, to prevent the enfilades of on the lines of defence fourteen toises to the the ricochet batteries. points Y, W, and upon each of the bases YI, W K, be described an equilateral triangle, the Sect. III.-OF THE SYSTEMS or M. Minyo, 1. NINYO, angles opposite to these bases, will be the centres BARON OF COEHORN. of the higher flanks Y I, W K. This officer, a contemporary with Vauban, was And if R be the intersection of the two lines a lieutenant general in the Dutch service, and of defence, RM bisected at S, and RC at Q; director general of all the fortified places belong- by drawing $ Q, v SQR will be half the tedaille; ing to the united provinces and along the Scheldt. and drawing from the point C, a line parallel He was the inventor of three systems of fortifica- to I Y, so as to meet the tower upon which the tion, in which he chiefly attended to the means mean Aank is described in the same manner as of flanking and covering the works as effectually the former. as possible, whilst those parts of the fortifications The parapets o. the three flanks, and those of which are advantageously situated for the be- the parts m V, V M, of the towers, are twentysieger's batteries, would not afford sufficient four feet thick ; the other parts M r,ram, but space for them. He also had for his object to sixteen ; and all the other parapets in general are facilitate an active and obstinate defence to the twenty feet. garrison; for which purpose he contrived such There is a wet ditch before the mean flank dispositions as would, in his opinion, enable the of six toises broad, and another behind besieged troops to oppose the besieged, within the towers of the same breadth, over which are the fortifications, with forces superior to his, and made two draw-bridges, parallel to the higher upon a larger front; besides securing the retreat faces. of these troops, and exposing those of the be-. The space X between the higher and lower sieger to the fire of the casemated batteries, co- faces of the bastions is a dry ditch, whose bottom tered caponiers, crenelled galleries, and coffers, is but six inches above the surface of the water in which are employed in the systems. Coenorn the wet ditch. |