their sports profitable; images, battles, and fortifications being then delivered to their memory, which, after stronger judgments, might difpenfe fome advantage. Sidney. 3. Addition of ftrength. Not much ufed.-To ftrengthen the infefted parts, give some few advices by way of fortification and antidote. Government of the Tongue. HISTORY of FORTIFICATION. THE origin of fortification is doubtless to be afcribed to that rapacious principle, which has influenced too many of mankind in all ages and nations to invade the rights and properties of those whom they confidered weak or defencelefs. In the firft ages of the world, men were dispersed over the earth in feparate families as is recorded in the patriarchal histories of the Jews and Scythians, who wandered from place to place, in fearch of pafture for their cattle. These families became fo numerous as to form large communities, which fettled altogether in one place; from whence villages and towns had their origin: but they found it neceffary, for the common fecurity, to furround thofe towns with walls and ditches, to prevent all violences and fudden surprises from their neighbours. This was fufficient for fome time, till offenfive weapons were invented, and conquering became a fabion. Then walls with loop holes were made at proper distances, in order to fcreen the defenders against the arrows of the affailants: but finding that, as foon as the enemy got once close to the walls, they could from no part be difcovered or repulfed; for this reafon they added fquare towers at proper diftances from each other, fo that every part of the wall might be defended by the adjacent fides of the towers. However, this manner of inclofing towns was found to be imperfect, because there remained still one of the faces of the towers which fronted the field that could not be feen from any other part, and therefore could not be defended. To remedy this, they made the towers round inftead of fqnare; imagining this figure to be the ftrongest to refift the battering engines, as well as to be better defended from the other parts of the wall. Notwithstanding the fuperiority of this method above the former, there ftill remained a part of thefe towers unfeen and incapable of being defended; which made them change the figure of the towers again; i. e. they made them fquare as before; but, inftead of presenting a face to the field as formerly, they prefented an angle; and thus they effectually found out fuch a difpofition of their works, that no part could be attacked without being feen or defended from fome other part. This laft method was long in ufe, and would in all probability have continued to this day, if gun-powder had not been invented: but the violence of the guns and mortars foon convinced the world, that fuch towers and walls were but a weak defence against these thundering engines; and that, as the nature of the attack was entirely changed, it was also neceffary to change the mode of defence. Ramparts were therefore added to the walls; the towers enlarged into bastions, and all forts of outworks have been fince added; fuch as ravelins, VOL. IX. PART II. counterguards, horn and crown works, and others of the like nature, to render the defence in some measure equivalent to the attack. But in fpite of all the improvements which have been made in the art of fortifying, fince the invention of gun-powder, that of attacking is still fuperior to it engineers have tried in vain to render the advantages of a fortification equal to thofe of the attack; the fuperiority of the befiegers fire, together with the greater number of men, generally obliges the befieged to fubmit sooner or later. The greatcft improvement made in the art of attacking happened in 1697, when M. Vauban firft made use of ricochet firing at the fiege of Ath, whereby the befieged placed behind the parapets were as much expofed to the fire of the befiegers as if there had been no parapets; whereas, before they had been fecure as long as the parapet was not demolished: and the worft is, that there can be no remedy found to prevent this enfilading, without falling into inconveniences almoft as bad as those which we endeavour to avoid. The art of fortification is divided into two parts; regular and irregular. PART I. OF REGULAR FORTIFICATION. REGULAR FORTIFICATION is that built in a res guiar polygon, the fides and angles of which are all equal, being commonly about a mufket-fhot from each other. Although authors agree as to the general form in the prefent manner of fortifying, yet they moftly differ in particular conftructions of the parts. As it would be fuperfluous to treat of all the different methods hitherto propofed, we shall explain thofe only which are most efteemed by the bet judges, and have been most generally practised. SECT. I. CONSTRUCTION of the MEAN FortiFICATION, according to M. VAUBAN'S METHOD. VAUBAN'S method is divided into little, mean, and great; the little is chiefly used in the conftruction of citadels, the mean in that of all forts of towns, and the great in particular cafes only. We fhall give the conftruction of the mean, as being most ufeful; and refer the reader to the table hereafter, for thofe dimenfions which are different in thefe feveral fortifications. Infcribe in a circle a polygon of as many fides as the fortification is defigned to have fronts; let AB, fig. 1, Plate CLVI, be one of the fides of half an hexagon, which bifected by the perpendicular CD; divide half of it AC into 9 equal parts, and one of thefe into 10 others; then thefe divifions will ferve as a fcale to conftruct all the parts of the fortification, and each of them is fuppofed to be a toife or fathom, that is 6 French feet; and therefore the whole fide AB is fuppofed to be 180 toifes. As the dividing a line into fo many equal parts is very troublesome, it is much easier to have a fcale of equal parts by which the works may be conftructed. If therefore, in this cafe, the radius is taken equal to 180 toifes, and the circle defcribed with that radius being divided into fix equal parts, or the radius being carried fix times round, we will have an hexagon inferibed; AB being bifested by Titt the the perpendicular CD as before, set off 30 toifes 14. Any angle whose point turns from the place from C to D, and draw the indefinite lines ADG, is called a SALIANT ANGLE, such as A. M.: and BDF; in which take the parts AE, BH, each e- any angle whofe point turns towards the place, qual to go toifes; from the centre E defcribe an RE-ENTERING ANGLE, fuch as b, F, N. arc through the point H, meeting AD in G, and from the centre H describe an arc through the point E, meeting BD in F; or which is the fame, make each of the lines EG, HF, equal to the dif. tance EH; then the lines joining the points A. B, F, G, H, B, wil' be the principal or outline of the front. If the fame conftruction be performed on the other fides of the polygon, we will have the principal or outline of the whole fortification. If, with a radius of 20 toifes, there be defcribed circular arcs, from the angular points B, A, M, T, and lines are drawn from the oppofite angles, E, H, &c. fo as to touch thefe arcs, their parts a b, bc, &c. together with these arcs, will reprefent the outline of the ditch. SECT. II. DEFINITION of TERMS. 1. The part, FEALN, is called the BASTION. 2. AE, AL, the FACES of the baftion. 3. EF, LN, the FLANKS. 4. FG, the CURTAIN. 5. FN, the GORGE of the bastion. 6. AG, BF, the LINES of defence. 7. AB, the exterior fide of the polygon. 8. CD, the PERPENDICULAR. 9. Any line, which divides a work into two equal parts, is called the CAPITAL of that work. 10. abc, the COUNTER SCARP of the ditch. II. A, M, the FLANKED ANGLES. 12. H, E, L, the ANGLES of the shoulder, or SHOULDER only. 13. G, F, N, the ANGLES of the flank. 15. If two lines be drawn parallel to the principal or outline, the one at 3 toises distance, and the other at 8 from it; then the spaceyx included between the principal one and that fartheft diftant, is called the RAMPART. And the space xx, contained by the principal line, and that near to it, and which is generally ftained black, is called the PARAPET. 16. There is a fine line drawn within 4 feet of the parapet, which expresses a step called BANqUETTE. N. B. All works have a parapet of three toifes thick, and a rampart of 8 to 10, befides their flopes. The RAMPART is elevated more or less above the level of the place, from 10 to 20 feet, according to the nature of the ground and the particular conftructions of engineers. The PARAPET is a part of the rampart elevated from 6 to 7 feet above the reft, in order to cover the troops which are drawn up there from the fire of the enemy in a fiege; and the banquette is 2 feet higher than the rampart, or about 4 feet lower than the parapet; fo that when the troops ftand upon it, they may juft be able to fire over the parapet.. or 3 17. The BODY of the place, is all that which is contained within the first rampart; for which reafon, it is often faid to conftruct the body of the place; which means properly, the conftruction of the baftions and curtains. 18. All the works which are constructed beyond the ditch before the body of the place are called OUTWORKS. of DIMNESIONS. Little Fortification|| Mean. || Great. 140 150 160 170 180 190 200 260 SECT. III. TABLE Sides of Polygons, 80 90 100 Perpendiculars, Faces of Baftions, 10 11 12 2225 28 Capital of Ravelin, 2528 30 In the firft vertical column are the numbers expreffing the lengths of the exterior fides from 80 to 260. In the 2d, the perpendiculars anfwering to these fides. In the 3d, the lengths of the faces of baftions; and in the 4th, the lengths of the capitals of the ravelins. The forts are mostly, if not always, fquares: for which reafon, the perpendiculars are made one 8th of the exterior fides; because if they were more, the gorges of the baftions would become too narrow. The little fortifications is chiefly defigned for citadels, which are commonly pentagons; the perpendiculars are made one 7th of the exterior fide: the mean is ufed in all kinds of fortifications, from an hexagon upwards to any number of fides: and the great is feldom ufed but in an irregular fortification, where there are fome fides that cannot be made less without much expense; or in a town 20 21 23 25 30 31 25 32 40 42 45 47 50 53 55 60 55 55 60 70 which lies near a great river, where the fide next the river is made from 200 to 260 toifes; and as that fide is less expofed to be attacked than any other, the perpendicular is made shorter, which faves much expense. The faces of the bastions are all two 7ths of the exterior fides, or nearly fo, because the fractions are neglected. In general, in all fquares the perpendicular is one 8th of the exterior fide, and all pentagons one 7th, and in all the reft upward one 6th. SECT. IV. Of the CONSTRUCTION of ORILLONS and RETIRED FLANKS. Defcribe the front MPQRST as before, and divide the flank into three equal parts, of which fuppofe Sr to be one: from the oppofite flanked angle M draw a line Mr, in which take the part mr of 5 toifes; take likewife R n in the line of defence MR. MR, produced equal to 5 toifes, and join nm, upon which as a base describe the equilateral triangle npm, and from the angle p, opposite to the bafe as centre, is defcribed the circular flank n m, And if Sr be bifected by the perpendicular 1, 2, and another be erected upon the face ST, at S; the intersection 2 of these two perpendiculars will be the centre of the arc which forms the orillon. The orillons are very useful in covering the retired flanks, which cannot be feen but directly in the front; and as thefe orillons are round, they cannot be so eafily deftroyed as they would be if they were of any other figure. SECT. V. CONSTRUCTION of RAVELINS or FIG. 2. Set off 55 toifes, from the re-entering angle O of the counterfcarp, on the capital OL, or on the perpendicular produced; and from the point L draw lines to the fhoulder AB; whofe parts LM, LN, terminated by the counterfcarp, will be the faces, and MO, ON, the femi-gorges of the ravelin required. This is Mr Vauban's method of contructing ravelins, according to fome authors: and others will have the faces of the ravelin to terminate on thofe of the baftions within three toifes of the fhoulders; which seems to be the best way, for these ravelinscover the flanks much better than the others. The ditch before the ravelin is 12 toifes, its counterscarp parallel to the faces of the ravelins; and is made in a circular arc, before the faliant angle; as likewife all ditches are in general. When the ravelins are made with flanks, as in Plate CLVI. fig. 3. the faces fhould terminate on thofe of the baftions, at least 5 toifes from the fhoulders. The flanks are made by fetting off to toifes from the extremities of the faces, from f to b, and from m to 1; and from the points b, I, the flanks k, p, are drawn parallel to the capital LO of the ravelin. There are fometimes redoubts made in the ravelin, fuch as in fig. 2. which is done by fetting off 16 toifes from the extremities of the faces on the femi-gorges from N to b, and from M to a; and from the points b, a, the faces are drawn parallel to thofe of the ravelin; the ditch before the redoubts is 6 toifes, and its counterfcarp parallel to the faces. SECT. IV. CONSTRUCTION of TENAILLES. A tenaille is a work made in the ditch before the curtains, the parapet is only 2 or 3 feet higher than the level ground of the ravelin. There are 3 different forts; the firft are thofe as in fig. 4. which are made in the direction of the lines of defence, leaving a paffage of 5 toifes between their extremities and the flanks of the baftions, as likewife another of 2 in the middle for a bridge of communication to the ravelin. The 2d fort are thofe as in fig. 5. Their faces are in the lines of defence, and 16 toifes long, befides the paffage of 3 toifes between them and the flanks of the baftion; their flanks are found by defcribing arcs from one shoulder of the tenaille as centre through the other, or on which are fet 10 toifes for the flanks defired. The 3d fort are thofe as in fig. 6. Their faces are 16 toifes, as in the fecond fort, and the flanks are parallel to thofe of the battions. The ufe of tenailles in general, is to defend the bottom of the ditch by a grazing fire, as likewife the level ground of the ravelin, and efpecially the ditch before the redoubt within the ravelin, which can be defended from no where else fo well as from them. The first fort do not defend the ditch fo well, as the others, as being too oblique a defence; but as they are not fubject to be enfiladed, M. Vauban has generally preferred them in the fortifying of places, as may be feen in the citadel of Lille, at Landau, New Brifac, and in many other places. The 2d fort defend the ditch much better than the firft, and add a low flank to those of the baftions; but as thefe flanks are liable to be enfiladed, they have not been much put in practice. This defect might however be remedied, by making them fo as to be covered by the extremities of the parapets of the oppofite ravelins, or by fome other work. As to the 3d fort, they have the fame advantage as the 2d, and are likewife liable to the fame objections; for which reafon, they may be ufed with the fame precautions which have been mentioned in the fecond, Tenailles are eteemed fo neceffary, that there is hardly any place fortified without them; and with reafon : For when the ditch is dry, the part behind the tenailles ferves as a place of arms, from which the troops may fally, and deftroy the works of the enemy and the ditch, oppose their defcent, and retire with fafety; and the communication from the body of the place to the ravelin becomes eafy and fecure, which is a great advantage; for by that means the ravelin may be a much better defence, as it can be supplied with troops and neceffaries at any time. And if the ditch is wet, they ferve as harbours for boats, which may carry out armed men to oppofe the paffage over the ditch whenever they please; and the communica tion from the tenailles to the ravelin, becomes likewife much eafier than it would be without them. SECT. VII. CONSTRUCTION of LUNETTES. FIG. 7. Plate CLVI. Lunettes are placed on both fides of the ravelin, fuch as B, to increase the strength of a place: they are confiructed, by bifecting the faces of the ravelin with the perpendicular LN; on which is fet off 30 toifes from the counterfcarp of the ditch, for one of its faces; the other face, PN, is found by making the femigorge, TP of 25 toifes; the ditch before the lunettes is 12 toifes, the parapet 3, and the rampart 8, as in the ravelin. There is fometimes another work made to cover the faliant angle of the ravélin, such as A, called bonnet, whofe faces are parallel to thofe of the ravelin, and when produced, bifect those of the lunettes; the ditch before is 10 toifes. There are likewise lunettes, such as D ̧in fig. 8. whofe faces are drawn perpendicular to thofe of the ravelim, within a third part from the faliant angle; and their femi-gorges are only 20 toifes. Thefe kinds of works may make a good defence, and coft no very great expenfe; for as they are Tttta fa fo near the ravelin, the communication with it is horn-work is 35 toifes, and the faces terminate very eafy, and one cannot well be maintained till on the fhoulders, or rather 2 or 3 toifes beyond they are all three taken. them and the ditch before the ravelin is 8 toifes. SECT. VIII. CONSTRUCTION of TENAILLONS. FIG. 9. Plate CLVI. Produce the faces of the ravelin beyond the counterfcarp of the ditch, at a distance MN of 30 toifes, and take on the counterfcarp of the great ditch 15 toifes from the reentering angle p to q, and draw Ng; then qNMp will be the tenailles required; its ditch is 12 toifes. that is, the fame as that of the ravelin. Some times a retired battery is made in the front of the tenaillons, as in B; this battery is 10 toifes from the front to which it is parallel, and 15 toises long. Retrenchments are commonly made in the tenaillons, fuch as O; their parapets are parallel to the fronts MN, and bifect the fide qN; the ditch before the retrenchment is 3 toifes; and there is a banquette before the parapet next to the ditch of about 8 feet, called berm; which ferves to prevent the earth of the parapet (which feldom has any revetment) from failing into the ditch. The ravelin, before which tenaillons are conftructed, must have its faliant angle much greater than the former conftruction makes them; other wise the saliant angles of the tenaillons become too acute; for which reafon we made the capital of this ravelin 45 toifes, and the faces terminate within 3 toifes of the shoulders, SECT. IX. CONSTRUCTION of COUNTER GUARDS. FIG. 10. 11. When the counterguard is placed before the ravelin, fet off 40 toifes on the capital of the ravelin from the faliant angle A to the faliant angle B, of the counterguard; and 10 from C to D, on the counterfoarp of the ditch. When the counterguard is before the baftion, fuch as in fig, 2. its faliant angle F is 50 toifes from the faliant angle E of the baflion, and the breadth near the ditch of the ravelin ro toifes as before. The ditch before the counterguards is 12 toifes, and its counterfcarp parallel to the faces. Counterguards are made before the ravelin on fome particular occafions only; but are frequently conf.ructed before the baftions, as covering the flanks wonderfully well. Some authors, as Mr Blondel and Mr Cochorn, will have them much narrower than they are here. SECT. X. CONSTRUCTION of HORN-WORKS. FIG. 12. Plate CLVI. Produce the capital of the ravelin beyond the faliant angle A, at a diftance AB of about 80 toifes; draw DBE at right angles to AB; in which take BD, BE, each equal to 55 toifes; and on the exterior fide DE, trace a front of a polygon in the fame manner as that of the body of the place, making the perpendicular BF 10 toifes, and the faces 30. The branches Da, Eb, of the horn-work, when produced, terminate on the faces of the baftions, within 5 toifes of the thoulders. The ditch of the horn work is 12 toifes, and its counterfcarp parallel to the branches; and in the front terminates at the fhoulders, in the fame manner as the great ditch before the bastions. Retrenchments are sometimes made within the horn-works, fuch as S, S; which are constructed by erecting perpendiculars to the faces of the ravelins, within 25 toifes of their extremities. This retrenchment, like all others, has a parapet turfed only with a berm of 8 feet before it; as likewife a ditch from 3 to 5 toifes broad. Fig. 13. When a horn-work is made before the baftion, the diftance DL of the front from the faliant angle of the baftion is Ico toifes, and the branches terminate on the faces of the adjacent ravelins within 5 toises from their extremities; all the rett is the fame as before. SECT. XI. CONSTRUCTION of CROWN-WORKS. From the faliant angle, A, fig. 1. Plate CLVII. of the ravelin, as a centre, defcribe an arc of a circle with a radius of about 120 toifes, cutting the capital of the ravelin produced at C; from the point C, fet off the cords CB, CF, each of them equal to 110 toises; and on each of which, as an exterior fide, conftruct a front of polygon of the fame dimentions as in the horn-work; that is, the perpendicular should be 18 toifes, the faces 30, and the branches terminate on the faces of the baftions within 25 toifes of the shoulders. The ditch is 12 toifes, the capital of the ravelins 35, and its ditch 8; that is, the fame as in the horn-work. Sometimes the crown-work is made before the baftions, as in fig. 2. The arc is defcribed from the faliant angle A of the baftion, with a radius of 120 toifes, as before; and the branches terminate on the faces of the adjacent ravelins within 25 toifes of their extremities; the reft of the dimenfions and conftructions are the fame as before. Horn-works, as well as crown-works, are never made but when a large spot of ground falls beyond the fortification, which might be advantageous to an enemy in a fiege, or to cover fome gate or entrance into a town. SECT. XII. CONSTRUCTION of COVERT WAYS and GLACIS. Although we have not hitherto mentioned the covert way, nevertheless all fortifications whatfoever have one; for they are eftecmed to be one of the most effential parts of a modern fortification; and it is certain the taking the covert way, when it is in good condition and well defended, is generally the most bloody action of the fiege. After having constructed the body of the place, and all the outworks which are thought necessary, lines are drawn parallel to the utmost counterfcarp of the ditches, at 6 toifes diftant from it; and the space m n, mn, included between that line and the counterfcarp, will be the covertway required. Fig. 3. There is in every re-entering angle of the counterfcarp a place of arms, ; which is found by fetting off 20 toifes from the re-entering and angle a, on both fides from a to b, and from a to c and from the points b, c, as centres, ares are described with a radius of 25 toifes, fo as to The capital of the ravelin before the front of the interfect each other in d; then the lines drawn from |