The new method of fortification, as practised by Monsieur de Vauban, Engineer General of France with an explication of all terms appertaining to that art / made English.

A NEW TREATISE OF Fortification, BOOK IV. (Book 4)

CHAP I. Of the Principal Angles of a Fortress.

THIS Book contains the Explication of the Parts of a Fortress, where∣of we have already spoken: By which are to be understood, the Cavaliers, the Streets, the Places of Arms, the Counter-Guards, the Ma∣gazines, Gates, Back-Doors, Draw-Bridges, Bridges, and other Things. But we shall first begin to trea•• of the Angles.

Sect. 1. To find the Angle of the Center of every Regular Fortress.

DIvide the Circumference of the Diameter, which con∣tains 360 Degrees, by the number of the Bastions of your Fortress, and the Product of that Division will make

[illustration]

the Overture, or Angle of the Center. For Example: Let us seek the Angle of the Center of a Pentagon; to which purpose, you must divide 360 Degrees by 5. For in regard our Fortress has no more than five Bastions, a larger Divisor cannot be taken: So that the Product of the Division being 72, we must say, that the Angle of the Center of a Pentagon has 72 Degrees of Overture.

Sect. 2. To find the Angle of the Gorge, as it is called af••er Vau∣ban's manner; or the Angle of Exterior Polygons.

TO find that Angle, there needs no more than to sub∣stract the Angle of the Center of the same Fortress of 180 Degrees, and that which remains makes the Angl•• of the Gorge. For Example: If you would know

[illustration]

the Angle of the Gorge of a Pentagon, you must from 180 Degrees substract 72; for that is the Angle of the Center of a Pentagon: Then observe what remains, which will be 108 De∣grees, and say, That the Angle has 108 Degrees of Overture.

Sect. 3.

AS for the Angle of the Bastion, and all the rest, it is impossible to know what their Overtures are, in re∣gard they are not always the same: So that it depends upon the knowledge of the Engineer to make the Flanks, so that they may form a good Angle of the Bastion, accor∣ding to which almost all the rest take their measures. Consult our Authors upon this matter. Nevertheless we shall here set down the Overtures of the principal Angles after our manner of Fortification.

In a Square.

	Degr.	Min.
(1.) The Angle of the Center is	90	00
(2.) The Angle of the Gorge	90	00
(3.) The Angle of the Bastion	63	00
(4.) The Angle of the Courtin	98	30
(5.) The Angle forming the Flank	81	30
(6.) The Angle forming the Front	112	30
(7.) The flanking Angle	67	30

In a Pentagon.

	Degr.	Min.
(1.) The Angle of the Center is	72	00
(2.) The Angle of the Gorge	108	00
(3.) The Angle of the Bastion	77	00
(4.) The Angle of the Courtin	101	50
(5.) The Angle forming the Flank	78	10
(6.) The Angle forming the Front	116	00
(7.) The flanking Angle	64	00

In a Hexagon.

	Degr.	Min.
(1.) The Angle of the Center is	60	00
(2.) The Angle of the Gorge	120	00
(3.) The Angle of the Bastion	87	00
(4.) The Angle of the Courtin.	106	00
(5.) The Angle to form the Flank	7••	00
(6.) The Angle to form the Front	121	40
(7.) The flanking Angle	58	20

In a Heptagon.

	Degr.	Min.
(1.) The Angle of the Center is	52	00
(2.) The Angle of the Gorge	128	00
(3.) The Angle of the Bastion	95	00
(4.) The Angle of the Courtin	102	30
(5.) The Angle to form the Flank	77	30
(6.) The Angle to form the Front	120	00
(7.) The flanking Angle	60	00

In an Octogon.

	Degr.	Min.
(1.) The Angle of the Center	45	00
(2.) The Angle of the Gorge	135	00
(3.) The Angle of the Bastion	100	00
(4.) The Angle of the Courtin	103	00
(5.) The Angle to form the Flank	77	00
(6.) The Angle to form the Front	121	00
(7.) The flanking Angle	59	00

In the Enneagon.

	Degr.	Min.
(1.) The Angle of the Center	40	00
(2.) The Angle of the Gorge	140	00
(3.) The Angle of the Bastion	100	00
(4.) The Angle of the Courtin	106	00
(5.) The Angle to form the Flank	74	00
(6.) The Angle to form the Front	125	00
(7.) The flanking Angle	55	00

In a Decagon.

	Degr.	Min.
(1.) The Angle of the Center	36	00
(2.) The Angle of the Gorge	144	00
(3.) The Angle of the Bastion	100	00
(4.) The Angle of the Courtin	93	00
(5.) The Angle to form the Flank	87	00
(6.) The Angle to form the Front	115	00
(7.) The flanking Angle	65	00

In an Hendecagon.

	Degr.	Min.
(1.) The Angle of the Center	33	00
(2.) The Angle of the Gorge	147	00
(3.) The Angle of the Bastion	100	30
(4.) The Angle of the Courtin	101	30
(5.) The Angle to form the Flank	78	30
(6.) The Angle to form the Front	125	00
(7.) The flanking Angle	55	00

In a Dodecagon.

	Degr.	Min.
(1.) The Angle of the Center	30	00
(2.) The Angle of the Gorge	150	00
(3.) The Angle of the Bastion	100	00
(4.) The Angle of the Courtin	101	30
(5.) The Angle to form the Flank	78	30
(6.) The Angle to form the Front	128	00
(7.) The flanking Angle	52	00

Sect. 4. Of the Angle of the Bastions.

THis Angle has occasioned great Disputes among the most part of the Ancients, who have Treated of For∣tification: For some were of opinion, that this Angle was to be always acute; others, that it only ought to be so in the Hexagon, and that it ought to be Right in Figures of more than 6 Bastions; and this was the usual practice of M. Antoine de Ville. Others there are who maintain the contrary, and say, That the acute Angle is never to be al∣lowed of, but in Figures that are under 6 Bastions, and that it always ought to be Obtuse in a Fortess which ex∣ceeds that number. True it is, that the greatest number have been for the right Angle; and it were a sort of Ig∣norance to maintain the contrary, Morsheus••r made choice of this Angle in a Square of 60 degrees, in a Pentagon of 72 deg. in a Hexagon of 80 deg. in a Heptagon of 85 deg. 43 m. in an Octogon to an Hendecagon of 90 deg. Freittag made choice of this Angle from a Tetteragon of 65 deg. to a Pentagon of 74 deg. from a Hexagon of 80 deg. to a Hep∣tagon of 84 deg. 17 min. from an Octogon of 87 deg. 30 min. and from an Enneagon to a Dodecagon of 90. But he soon altered his opinion, maintaining that this A••gle ought to be from a Tetteragon of 60 deg. to a Pentagon of 69; from a Hexagon of 75, to a Heptagon of 79 deg. 17 min. from an Octagon of 82 deg. 30 min. to an Enneagon of 85 deg. to a Decagon of 87 deg. to an Hendecagon of 88 deg. 38 min.

to a Dodecagon of 90 deg. Goldman makes use of this Angle for a Square of 65 deg. for a Pentagon of 69 deg. for a Hexagon of 75 deg. for a Heptagon of 79 deg. 17 m. for an Octogon of 82 deg. 30 min. for an Enneagon of 85 deg. for a Decagon of 87 deg. for an Hendecagon of 88 deg. 38 min. for a Dodecagon of 90 deg. Pascha takes it for a Square of 60 fathoms, and augments it still by five, according as the Polygon gains more of the Side. But they who have been accounted most skilful in the Art of Fortification, were always, as I have said, for the Right Angle, thô it be alledged, that in making it Acute, there is room for more Firing from the Curtains; or that in making it Obtuse, it is more capable to withstand the Enemies Batteries, and the Injuries of Time. The reason that kept them so fix'd to this Opinion, was, that in their time they made their Breaches with the Cannon, so that this Angle being Right, it had all the perfection that could be desired; whereas the making it Obtuse, di∣minished the Capaciousness of the Bastion, and of its Flank; besides, that the same Battery could play upon both Fronts: And by making it Acute, the Point of it was so soon broken by the frequent discharges; more especially, if several Guns played at a Time; besides, that bad Weather more easily ruined that Point. But to speak the truth, we ought to believe, that this Angle, whether Right, Acute, or Obtuse, ought never to trouble our Thoughts, provided it be not less than 60 degrees, nor much more than 100: For the Breaches are now made by Mining, wherein there is ••o more trouble to carry the Point of a Bastion with an Obtuse Angle, than with an Angle either Right or Acute. Moreover, there is this in it, that Breaches are rarely made in the Point of a Bastion, but in one of the Fronts, to the end, that in passing the Moat the Assailants may not be exposed to more than one Firing; so that provided the Angle be well able to resist the Injuries of Time, it is enough. However, much more than 100 degrees are not to be exceeded, because that being more open, it would require the Capital Line to be short; in which case, the Bastion would not have room sufficient.

Sect. 5. Of the Angle of the Curtain.

ENgineers cannot agree concerning the Overture of the Flank; so that every one orders it according to his Fan∣cy. Erbard makes the Flank perpendicular to the Faces of the Bastions; and his Reason is, because the Flanks, being oblique above the Curtain, that is to say, making an acute Angle with it, are much more exposed to the Enemy, and consequently more difficult to be ruin'd, as not being batter'd by the Cannon but very obliquely: But granting that this were so, it is no less a Truth to say, that as they are but little expos'd, so neither do they not survey very far; and it is im∣possible to make good Embrasures upon a Parapet, ordered after that manner. For to play the Cannon above the Para∣pet, is to make it impossible to preserve it in a good condition; besides that a Flank disposed after that manner, can never de∣fend the Passage of the Moat, nor flank the Breach, nor in the last place, uncover the covert Ways. As for Monsieur le Chevalier de Ville, who makes the Flank perpendicula•• to ••he Curtain, he has more Reason for what he does, than Erbard; though his Fla••ks are less than those which Mon∣sieur Vauban makes use of, and that they do not batter the Moat sufficiently, nor the Counterscarps, which is the most essential part of the Defence. Besides, it is but too well found by Experience, that when the Counterscarp is gained, the rest holds out but a short time; the Reason of which, if it be demanded, is because the disposing of the Places is so disadvantageous, that one Day sees them reduced to D••st; and the Embrasure•• made upon these Parapets, perpendicular to the Curtain, are too acute; especially if it be required that they should clear the covert Ways. I know it may be said, that it is easie to m••ke an Orillon, or Ear, and a re∣tired Flank in a circular fashion: But the Orillon will be too feeble, unless you allow it the half of the Flank, and the remainder will not suffice for its Defence, not having room enough for several Pieces to be placed upon it; besides that,

there must be a mixture of great and small Shot, which will cause an inevitable Trouble.

Monsieur Pagan, a Person experienced to perfection in the Art of War, and one who has jus••ly acquired the Reputation of being one of the most skilful Engineers of our Time, was the first that alter'd the disposing of Flanks perpendicular to the Curtain, by allowing them much more overture; for he makes them perpendicularly upon the Line of Defence; and he gives very good Reasons for it in his Book of Fortificati∣ons; where he says, That his being present at above twenty Sieges, convinc'd him, that Flanks perpendicular to the Cur∣tains, were of little dura••ce: And he wonders that the Re∣putation given to the Holl••nders, for their Perfection in the Art of Fortification, should be so great, ••ince the Places for∣tified according to their Method, make so little Resistance; and for that there is not one which is well defended from the Canon: Nevertheless•• we may presume to say, that Monsieur Pagan'•• 〈…〉〈…〉 altogether without defects; for the Enemy 〈…〉〈…〉nk so dispos'd, before he comes upon the covert 〈…〉〈…〉 ••efore to make the best of all the Advantages wh〈…〉〈…〉: one and the other produces in his defence, Monsieur Vauban allows an Overture to this An∣gle, from 98 deg. to 106, as may be seen, Book IV. C. ••. Sect. 3. For by this means the Embrasures made in the Pa••rapet in this Flank, perfectly uncover the Moat, and the covert Way. And though Monsieur Vauban should not have made this Flank in a crooked Line, by means of the Orillon, and the retired Flank, however it ought to be preferr'd before others; because the Ravelin covers the Overture which is allowed it above the Perpendiculars to the Curtain, and con∣sequently it is not too much exposed; b••••ides that it conside∣rably enlarges and diminishes the Faces, which are the wea∣kest Parts of a Fortification.

CHAP. II. Of the Flank.

HERE we must repeat what we have already said, That though the largest Flanks are the best; nevertheless it is a Thing disputed among the Engineers. Morsheuser made th•• Flank to a Square of 16 Fathoms; to a V, of 18; to a VI, of 20; to a VII, of 22; to an VII, as far as a Dodecagon of 24. Freittag made it to a Square of 12; to a V, of 14; to a VI, of 16; to a VII, of 18; to an VIII, of 20; to IX, of 22; to X, of 24; which Length he retains also in Polygons of 11 and 12 Bastions. Goldman made it a Square of 12; to V, of 16; to VI, of 1••; to a VII, of 20; to an VIII, of 22; to a IX, ••ll he came to Polygons of 12 Bastions of 24 Fathoms. In ge∣neral, the H••llande••s make their Flanks to a Square of 16, Fathoms, 2 Feet; to a V, of 18 Fathom, 2 Feet; to a VI, of 19 Fathom 2 Feet; to VII, 19 Fathoms 5 Feet; to an VIII, 2•• Fathoms 1 Feet•• to a IX, of 22 Fathoms 1 Foot and a half; to a X, 23 Fathoms, 2 Foot; to XI, of 24 Fathoms, 2 Feet. Monsieur the Count of Pagan, allows the Flank in a Square, 19 Fathoms, 1 Foot•• to a V, 24, &c. as you may see, L. 3. C. 16, & 17.

CHAP. III. Of the Faces.

AS the Face is the most dangerous Part of a Fortress; and for that it is ex••reamly expos'd to the view of the Ene∣my, 'tis requisite that it should be as short as may be; for that, by how much it is the more advanced towards the Field, by so much it is the more liable to be at••ack'd: Whence it c••mes to pass tha•• the Enemy of ••••••e generally makes

choice of that Part, to begin his Breaches. As to the length of the Faces, the Engineers differ as much one among ano∣ther, as they do about the Flanks. Adrian M••tins would have the Face to carry two third parts of the Curtain. Mon∣sieur, the Count of Pagan, allows it in a Square 55 Fathoms, and permits the same Length for the Polygons. Freittag would have the Face to be always 48 fathoms, according to the practice of all the Hollanders. As for the Length of the Faces, after Vauban's Method•• see Chap. 16. of the Third Book,

CHAP. IV. Of the Orillon, and Flank retir'd; together with the Brisure, or Place where the Great Guns are to be planted.

AS for what concerns the erecting of the Orillon, and Flank retir'd, according to Monsieur de Vauban's Method, there needs no more than to read what he has written there∣upon in the Second Chapter of his Third Book. But here is a new Method; which though it be not better, however it is as good.

1. After the Out-Lines of the Fortress are drawn, divide the Flank of one of the Bastions into three equal parts, and the Face of the opposite Bastion into two, as, A, ••, B, C.

2. Draw from the Point B, which makes the middle of the Face, a Line through the third part of the Flank, which is the nearest to the Angle of the Shoulder D, prolonged in the Body of the Bastion of 5 fathoms, as DE.

3. Divide this same Third part of the Flank, into two equal parts; as FG, and GD•• from which Point G, erect a Perpendicular of about two fathoms, as GH. Lastly, Set the Compass upon the Point H, and so draw the Rounding of the Orillon, joyning FD, together.

4 Draw from the re-entring Angle of the Moat P a streight Line through the Angle of the Curtain L, prolonged in the

Body of the Place, of an equal bigness to the Line DE; that is to say, of five Fathoms, as, KI; to the end that you may have the Brisure, where you may place the piece of Cannon that points towards the Half Moon, & cannot be batter'd from the Field; because it is, as it were, covered by the Ravelin. Lastly, To make the Rounding of the Flank retir'd, take the Distance KE, between the Points of the Compass, and make Sections toward the Moat, in L; from whence after∣wards draw the Arch from K to F.

It cannot be said, but that these Orillons are very good; for these Roundings give less advantage to the Enemies Can∣non, and enlarge the room, as well for placing the Cannon, as for the Musketeers. If you object, That the Distance from that part where the Enemy may pass the Moat, is too great. I answer, That the principal Defence of the Small Shot to hinder the Passage of the Moat, consists in the Te∣n••ille; where you may set a Body of Musketeers, to fire con∣tinually.

Upon this Method, Monsieur de Clermont observes, That the Orillon of the Square would be too little, if you allow it no more than the Third Part of the Flank, as to the Poly∣gons; and therefore he requires Two Fifth Parts of the same Flank, for the Orillon. See the Plate P. Fig. XXII. at the end of the Third Book.

CHAP. V. Of the Curtain.

IN regard that the Curtain ought to cover the greatest part of a Work, it is requisite that it should be of a reasonable Length; that is to say, that it should never be shorter than Sixty Fathoms, and never longer than an Hundred. M••r∣sh••user allows it 72 Fathoms, and Freittag as much, Gold∣man would have the Length to be of 96 Fathoms; Anthony de Ville 100. Tieu makes it 74 Fathoms in Length; Himsel 84. Monsieur de Clermont allows it Three Fifth Parts of a Poly∣gon.

The Count de Pagan 60 Fathoms. Monsieur de Vau∣ban forms it according to the Plurality of the Bastions. As you may see Lib. 3 c. 17.

As to the Figure of the Curtains there are some Engineers, who will have them ••o be, as is mark'd at the Letter A; of which the Construction is such. See the Plate P. Fig. XXII. at the end of the third Book.

1. Divide the Line AB into •• equal parts, as AD, DM, NC, and CB, and take •• for the Demi-Gorge, as BC, AD.

2. Divide the same Line AB into three equal parts, and take one for the Capital, as BE, A••.

3. Where these three Parts are marked, as at R and G, bring down from the Points R, G, two Perpendiculars, of which se•• each have the third part of the Capital Line for its length, as RH and GI, and then joyn H and I toge∣ther by a Right Line.

4. Make upon the Points D and C, the Angle of the Cur∣tain of 100 degrees, and allow to the ••lank the length of the Demi-Gorge, •••• DP and CQ. This being done, joyn EQ and DP together, to have the Faces. The defects of the Curtain are, 1. That it is too short. 2. That the ••ortification takes up too much room. 3. That it renders the Bastion too Acute.

Others there are that form an Angle without side, as that which is marked with the Letter B. The Construction of which is after this manner.

1. Divide the Line AB into five equal parts, as AC, CD, DE, EF, and FB.

2. Divide the first Line AB into three equal parts, and allow one for the Capital, as AI, and BK; then join HI and BK together, to gain the Faces.

3. Divide the Curtain CF into two equal parts, and up∣••n the middle, marked with the Letter L, erect a Per∣pendicular; which has the half of the Face GK; as LM.

4. Draw from CF two streight Lines to the Point M, and your Curtain will be made. See the Plate P. Fig. XXIV.

••••hers make the Curtain of a C••rcular Figure within••s••de,

like that which is marked C: The Construction of which is as follows. See the same Plate. Fig. XXV.

Having observed what has been said touching the three first Points of the Preceding Curtain, take the Extremities of the Curtain BC, and make two Arches to cross or cu•• one another underneath; and from this Point of the In∣tersection draw an Arch, from one end of the Curtain to the other.

Lastly, There are others that form the Curtain of a Cir∣cular Figure without side, like that which is mark'd D. The Construction of which is like to that which we have already describ'd, only that here you make the Intersection above the Curtain in E: From which Point you afterwards draw the Arch from one end of the Curtain to the other.

The Breast Curtains are those which are drawn streight out-right from one Flank to another. See the same ••lank P•• at the end of the third Book. Fig. XXVI.

CHAP. VI. Of the Parapet.

IN regard that this Work is raised to cover the Cannon and the Soldiers which defend the Place, it must be allowed a rea••onable heighth and breadth. Cellarius allows it six Feet in heighth, with a Foot of sloping within side•• to the end the Soldiers may be able to stand the better when the Parapet is reared after that manner. The heighth without side from the Cord••n ought not to be above four Feet, because the ••loping which is made by those different Heights, inward and outward, gives the Soldier an easier view of the Co∣vert-ways, and the Moats that are before him. As for the Thickness of the Parapet, Monsieur Clermont allows it for the Basis, the third part of the Basis of the Rampart. The Count de Pagan makes it three Fathoms broad. Of which opinion are several others, as Goldman, Fr••ittag, and Mon∣sieur Vauban himself. So that we may boldly say, That

the Thickness of the Parapet is good, when it is not less than 18 Feet, nor broader than 24. For being weaker, the Parapet cannot long resist the force of the great Shot, which would soon level it with the Earth•• and being thicker, it would hinder the Soldiers from the sight of the Moat and the Covert way.

If you would line the Parapet, it must be allowed a little ••loaping, that the Soldiers may have the better footing. The best Lining of Parapets is with Turf. As for the Earth or Mould which you are to make use of in erecting a Parapet, it is very requisite to mix it with Withy Twigs, or Brambles, and to sow it with any Weeds that take a deep root, to bind the Earth together, so that the Cannon may not easily crumble it down. Hay of Burgundy is also very good for this purpose, in regard that there is no Plant that puts forth more or deeper Roots.

CHAP. VII. Of the Banquets.

AT the foot of the Parapet, upon the Plat-form, are usu∣ally made two little Steps or small Banks, of which the first is about two Feet broad. Goldman makes it four Feet, Fr••ittag 3. the Count of Pagan 2. Monsieur Clermont the same; and one Foot, and one Foot and a half high•• wherein they all agree. There are two made, for that the Soldiers are not all of an equal heighth. So that the low Men are placed upon the upper Step or Bank next the Para∣pet, and the taller upon the lowermost: so that every one may have a view from the Parapet, and discharge at his ••ase.

CHAP. VIII. Of the Rampart.

THIS Work is the Principal Piece of a Fortifica∣tion; and therefore the Rampart ought to be higher and broader than any of the rest of the Parts. Fournier allows for the Breadth of the Rampart from 15 to 25 Paces; and for the Heighth, from the Level of the Field from 15 to 25 Feet. Freittag takes for the Base of a Square 9 Fathoms: of a Pentagon, 10. of a Hexagon, 11. of a Heptagon, 12. of an Octagon, 13. of an Enneagon, 14. and observes this Breadth in all other Polygons. The Heighth of the Ram∣part he thinks sufficient if it be but 3 Fathoms; and he raises the said Rampart above the level of the Feild three Fathoms. Monsieur Clermont would have the fourth part of the Face allowed for the Base of the Rampart, or in the Feild from 8 to 12 Fathoms: believing that a larger breadth would not only be useless, but also prejudicial, by reason of the great space of Ground it would take up, and the vast quantity of Earth it would require. Monsieur de Vauban never makes the Basis larger than 11 Fathoms, alledging the same reason that Monsieur Clermont brings. The heighth of his Rampart never exceeds four Fathoms, whether to cover the Houses of the Place, or to command the Enemies approaches: For be∣ing lower, the Garison within could never command the Enemies Works. If they 〈◊〉〈◊〉 me that in some places a higher Rampart is requisite; I answer, That a good Cavaleer sup∣plys that defect, without raising the whole Rampart any higher. The upper Breadth of the Rampart ought to be from 4, to 6 Fathoms; for being too narrow, it would re∣quire that the Parapet should be made too broad to consume the rest of the Earth, appointed for the Rampart; besides that it would be prejudicial, because too broad a Parapet hin∣ders the Soldiers from the sight of the Moat; and being too large, the remainder of the Earth would not suffice to make

a good Parapet, which is also very dangerous. As for the sloaping of the Rampart, it has been said above, That there ought to be allowed ••o the Talu•• or sloaping of the Rampart, as the Earth tumbling down from the top to the bottom takes up of itself. For every Body knows, th••t, according to the badness of the Earth, the sloaping ought to be more or less, the better to sustain the Rampart. The best Earth is that which is called Grey Clay, next to that the slimy Earth, be∣cause that by reason of their clamminess, th••y bett••r resist the inconveniencies of Heat and Rain; besides they bind ex∣actly well together, support themselves with little sloa∣pi••g, and feed the Roots of Weeds and Grass better. To every foot of Earth, where the Rampart is raised, two ••ranches of Willow are to be set no bigger than a Man's Thumb: Besides that, the Earth is to be so hard rammed down, that it may sink four or five Inches, and that there remain not above seven or eight. Lastly, You ought to sow with Hay-Seed and Weeds upon the outside in every Row, to the end the Earth may intermix with the Roots. Nor is there any Herb that casts forth more or deeper Roots than the Spanish Tre••oyle, or winged Clover. Moreover, you ought to erect the Pla••form so, that the Plane of it may decline somewhat towards the City, to carry off the Wa••er. When you plant Trees upon the Rampar••, it is a great Ornament in time of Peace, and a good Provision in time of War. There are some Engineers that do not like this Advice•• for they say that the Wind makes such a noise, when the Branches hit one against another, that the Men can h••rdly hear one an∣other: besides that, it is a gr•••••• hindrance to the Centinal, whic•• is a considera••ion not altogether to be rejected. Last∣ly, We cannot pass by in silence the Fancy of some Men, who pr••portion the thickness of the Rampart to the number of the B••stions of the Fortification, as if a Hexagon ought not to have as good •• Rampart as a Decagon. I would ••ain ask them, whether small places are not attackt with the same A••ms as great ones••. If they answer, That there is more Earth taken out of the Moat of a large Place, than a small one; we r••ply, That it may be spent upon the Glacis: ••or that the larger the Glacis••s are, the better they are••

CHAP. IX. Of the Embrasures and Merlons.

MANY have proposed several sorts of Embrasure••, but the best are those which are streight and narrow within side, and wide towards the Field; to the end that the great Guns may play with more ease toward the right and left. The M••rlons, to the end that they may be good, ought to be made of Earth, the most easie to be tempered that may be: And this Earth ought also to be mixed with Withy Twigs, or Brambles, provided they take Root, after which they are to be lined with good Tu••ff.

CHAP. X. Of the Moat in the Body of the Place.

IN regard that every Fortress ought to be environed with a Moat, we shall briefly examine which sort of Moats are first to be preferred. Some make them broad, others narrow, one draws the Mo••t parallel to the Faces, another draws them narrower toward the Point of the Bas••ion, than in any other Places. Las••ly, one is for a dry Ditch, another for a Moat that is full of Water. One prefers a Moat very deep, but not so broad; another would have it broad, but not so deep. Let us examine every one of these in order. The Count of Pagan makes his Moat for a Tetragon 16 Fathoms broad; and for Polygons of 20, his depth does not exceed 4 Fathoms. Mons••eur Clermont takes from 16 to 20 Fathoms, for the Breadth of the Moat, without any regard to the Plura∣lity of Bastions; and makes it hollow from 18 to 20 Feet. Fou••nie•• would have it broad from 15 to 25 Paces, and deep from 15 to 25 Feet. Cellarius makes his Moat 3 Fathoms deep,

and broad at the top about 19, and at the bottom near 13. Monsieur de Vauban prefers Monsieur Clermont's Way be∣fore all the rest, as to the Breadth and Depth of the Moat: For as to the way of drawing out the Moat, Monsieur Cler∣mont makes it narrower toward the Point of the Bastion than toward the other Parts; more especially if the Flanks are large; for he says that otherwise, it would be requisite that the Moat should be as large as the Length of the Flank, or else much more narrow; and in the first case there would be a ne∣cessity of making it very shallow, which would render it de∣fective, for that the Enemy would easily shoulder himself into it. And supposing it were of a reasonable Depth, there would be Ground which no body would know what to do with, by reason of the extraordinary Wideness. And in the second case, there would be one side of the Flank, that would not uncover the Moat, which would be against the Rules of Forti∣fication. Others answer first, that if the Moat were as large as the Flank, with a moderate Depth, that Wideness would hinder the Enemy from crossing the Moat without great loss of his Men. But if the depth were a little more than ordina∣ry; and it should be asked, what should be done with the Earth taken out of the Moat; they reply, ••twould make the Glacis. The learned may judge as they please; but for my part, I hold with them, that are for making the Moat parallel to the Line of Defence. If they still object•• that the rounding of the Moat being as large as in other Places, all the whole Curtain and Face of the opposite Bastion cannot be discovered; we must answer, that if they would uncover those Parts above the rounding, they ought to make no Moat at all, because the Point of the Bastion it self is not proper for that. Add to this, that if the Moat be made narrower toward the Point of the Bastion, the Enemy having once gain'd the Point, the Earth of which is fill'd one part of the Moat, he will easily pass it by, throwing B••vins over the Ruins of the Bastions, which will shew him, as I may so say, the way to enter directly into the Bastion.

The next Question is, whether a Moat full of Water is to be preferred before a dry Moat; which a distinction between the great and small Places will quickly decide. As for great

Fortresses, it cannot be deny'd but that dry Moats are to be preferred before those full of Water. Some will object, that a Moat full of Water secures a Place against Scaladoes and Surprizes; besides that, is very hard to be filled up; and that it affords great Trouble to the Enemy, that would either pass it, or cover himself, or fight within it: And that on the other side, besides that a dry Ditch is extremely exposed to Surprizes, very easie to be filled up, and no less easie to be passed; it is very proper to cover the Enemy in making of Mines, by means of which he may blow up a great Part of the Place. But I answer to this, that as well a Moat full of Water hinders the Sallies of those within, without the help of Boats, which make so great a noise, that 'tis impossible but the Out-Sentinels near the Place besieged, must hear it; and the same that is to be said of the Sallies, is to be said of the Retreats. Beside, if the Water that fills the Moat be not a running Stream, it begets an unwholsome Air, causes fre∣quent Distempers, and renders the Soldiers less courageous, by reason of the noisome Stenches that arise out of it; and on the other side, besides that, a dry Moat is more commodious for Sallies, and safe Retreats; there is no Fear of Sickness proceeding from noisome Water, and unwholsome Air. To say something of the Convenience of Mines, which the Ene∣my has to make, you must make a Cuvette, or little Dike in the middle of the Moat from 15 to 20 Foot broad, and very deep; for the deeper it is, the better it is: Surround it with a good Parapet with Palisadoes round about; and so you will be secure from Mines and Surprizes. As for little Fortresses, a Moat full of Water is better than a dry, because Sallies, Re∣treats, and Succors, are not so necessary as in great Places. The Moat is also to be rounded before the Point of the Bastion, to the end that it may be of the same Wideness quite through, and that it may not advance too far into the Field; which it would do if it were pointed. You may also set a Corps du Guard upon this Rounding, the better to defend the Covert way. Lastly, When you would line the Moat, they never allow it any great Talus or Sloaping; only they al∣low it such as the Earth of the Rampart, and the Moat gives it of it self.

CHAP. XI. Of the Moat belonging to the Outer Works, and the A∣va••t-Moat.

THe Moats belonging to Outer-Works ought to be neither so great, nor so deep, as that which belongs to the Bo∣dy of the Place: For a Wideness of 12 Fathoms suffices for these Moats, being hollow from 12 to 15 ••eet.

In short, there are some Engineers, who make a little Moat about the Glacis, though others practice quite contrary. The first pretend that the Earth taken out of the Moat, serves to fortifie the Glacis, and secure the Covert-way. On the other side it is said, that the Avant-Moat serves only to hinder the Sallies and Retreats of the Garrison: and this Reason prevails; for if you have need of Earth, the better to secure your cover'd Way, you may make the Moat of the Body of the Place deep, and employ the Earth which you take from thence, for that purpose. If you think that this Moat pre∣vents Surprizes, and the Approaches of the Enemy; I an∣swer, that a good wide Glacis will do the same, without being at so much Charge for an Avant-Moat Nevertheless sometimes they are constrained to environ the Glacis with such a Moat: They make it five Fathoms wide, and two deep. Such a Moat as this you may see about the Citadel of Strasbur••••.

CHAP. XII. Of the covered Way, and of the ••lacis.

A Good Covert way will require at least five Fathoms in Breadth, especially if the Ground will permit it; for one broade•• is useless and prejudicial, unless its Parapet be higher than ordinary; otherwise it is easily pie••ced by the

Enemies Batteries: And one less wide, is defective in this•• that there is not room for the great Guns and Men, but one will hinder the other. Besides, that when it is too narrow•• it is not flanked on so many Parts a•• it ought; and it may be said, that this part must be then too much in view of the Enemy, whose chiefest Effort in a Siege it is, to make him∣self Master of the Covert-way.

This Covert-way has no other Security than the Glacis, which serves it for a Parapet round about. The Wideness of it ought to be at least from 36 to 40 Fathoms, losing it self insensibly in its Inclination towards the Field. But the better to secure the Covert way, we must say that the largest Glacises are ••he best; for that by this means, the Enemy lies more open; and the less it has of Sloapings, the better they are, because the small Shot is the more secure in the Co∣vert way, and does more Execution. In short, there is no∣thing to be suffered about the Glacis, that may favour the Enemy in his Approaches: So that if the Glacis be higher than five Foot above the Covert way, you must put one or two Banquets below, as need shall require for the short statu•••• Soldiers.

CHAP. XIII. Of False Brayes.

HEre it is, that some will ask me why the French admit no False Brayes in their Fortifications, as being a second Defence, and an admirable Work to dispute the Counterscarp with the Enemy, and to hinder him from crossing the Moa••. Moreover it is certain, that small Shot does more Execution from a low than a high Place. Besides, that the small Shot placed in the False Bray, doubles the Defence of it, as that Work doubles the Defence of the Place. But if you talk of the Defence; Why do you then put the Counterscarp before the Faces, knowing that those Parts defend nothing? You will answer, that this is to dispute the Passage of the Moat.

But consider, that the Enemy having broken the Parapet of the Point, may afterwards pierce with his great G••ns the Walk that runs all along the Face: Besides that the ruining of that Work is very advantageous to the 〈◊〉〈◊〉, who would willingly have wherewithal to fill the 〈◊〉〈◊〉. As for the part of the False Bray that is before the Curtain, it is no longer good, because it does not flank the Faces of the Ba∣stions, nor hinder the Passage of the Moat, which is objected always for the principal Reason. Nevertheless the remain∣der of that Work, which is before the Flank, will be good: But know that this part is easily rendered unserviceable, by the Ruine of the Rampart, and the Parapet of the Flank, which falling within side, fills up its Platform: And if the Rampart be lin'd, the Splinters of it maim the Soldiers, that guard that Flank of the False Braye. To remedy which Defects, the French now adays erect Tenailles in the Moat before the Curtain, and before the Flanks separated from the Body of the Place, by a little Moat, to the end the fall of the Rampart of the Body of the Place may not kill or wound those that are in it, being lined with Walls There is nothing of all that you talk of False Brays, that can be attributed to these Te∣nailles; besides that they cast not the half of what those o∣ther Works do.

CHAP. XIV. Of Cavaleers.

CAvaleers are one of the best Defences of a Place, because they most notably scowre the Field, which obliges the Enemy to open his Tre••ches at a great distance, in regard these are as so many second Bastions, which are opposed to the Enemy. And moreover that they defend the Passage of the Moat, command the Covert••way, and above the Glacis; 'tis certain, that being well disposed, they may defend the Head of the Breach, which the Enemy shall make in the Face of the Bastion, wherein those Cavaleers are erected. Now

[illustration]

A Figure shewing all the angles in a Square

[illustration]

A Draught & Square of Vaubane.

[illustration]

For § 3: Book: III Chap:V. Fig: VI.

[illustration]

For § 2. Book: III Chap:V. Fig: V.

[illustration]

For § 4 Book: III Chap:V. Fig: VII.

in regard that Opinions are different, as well in respect of the place where ••hey are to be set, as in regard of their Figure. Let us see the Reasons both of the one and the other.

1.

There are some that would have the Cavalcers plac'd upon that part of the Curtain•• which discovers the Face of the op∣posite Ba••tion; that is to say, upon the Lines of the second Flank, as A•• the Construction of which is such. See the Plate Q, Figure XXVII.

1. Bring down a streight Line perpendicularly under the Flank, and upon this Line put two third parts of the Demi∣gorge; as A, B.

2. Divide the Line AB into two equal parts; as, AC, CB; and prolong perpendicularly the Point C, till this Prolongation be equal to the Demi-gorge; as, C, D.

3. Bring down also a Perpendicular from the Point D, of the Length CB; as, DE; and at length join BE, toge∣the•• by a streight Line.

4. Having rais'd the Cavaleer to a just Height, they give it a Parapet of th••ee Fathoms, and two Banquets, as is usual.

1 But it may be objected against this Situation, th••t the Cavaleer does not flank, but very obliquely•• and by conse∣quence, that the Effects of it are of little consequence.

2. That the Ruines which the Enemy's Cannon will make, as being oppos'd to it in Front, falling between the Curtain, and the Cavaleer, will hinder the Execution of the Small Shot of th•• Second Flank.

II.

1 Others lo••ge the Cavaleer in the middle of the Curt••in, and give it a Triangular Figure; alledging, That in that part•• one and the same Cavaleer may flank two Faces of the B••stions. To which it is answered, That a Cavaleer cannot be erected after that manner, but in Places which have more than half the Curtain for the sec••nd Flank; which would be very difficult, unless it were in Ci••ies where the Angles of the Polygon are of a very large Ove••ture. For to say, we o••ght to make these second Flanks ve••y large, as well to a••gment the Firing from the Curtain, as to g••in room fo•• placing of th•• Ca∣valeer,

this is to make Bastions in a Place, that serve for nothing; because, that by this means, the Flanks are made so small, that they seem to be only for Ornament.

2. That the Enemy stands in no fear of the Firing from a Cavaleer dispos'd after that manner, when once he is lodg'd upon the Counterscarps, because it is too high, and the Can∣non cannot plunge low enough.

The Construction of this Cavaleer is such. See the Plate Q. Fig. XXVII, B.

1. From the Curtain bring down a perpendicular Line•• and put there above 14 Fathoms; as, AB.

2. Take that Distance, and draw from the Point B a Circle.

3. Divide this Circle into Three equal parts, beginning from the Point A; as, AC, AD, and CD; which joyn together by right Lines; and this shall be the Base of the Cavaleer.

4. Draw on the Sides AC, and AD, the Base of the Para∣pet of 3 Fathoms. But it is to be observ'd, That these Cavaleers are not to be erected but from 9, to 10 Feet above the Plat∣form of the Rampart, unless there be very strong Reasons to raise it higher. In the mean time,'tis very true, that this Cava∣leer is not better than the preceding, because the Angles of it are very acute; for when the Angle A is carried away, all the rest is worth nothing; since neither Cannon nor Soldiers can subsist up••n the side AC, and AD, by reason of the Enemy's continual playing upon them.

III.

Some raise the Cavaleers upon the Platform of the Ba∣stion, and dispose it in such a manner, that the Faces and Flanks of the Cavaleer are parallel to the Faces and Fla••ks of the Bastion; as C. The Advantages that pro••••••d from this Disposition, are, that the Enemy being got u••••n the op∣posite Counterscarp, will be troubled to lodge his Cannon there, by reason of the Cannon upon the Flank, and upon the C••valeer; which playing without ceasing, will dismount the Enemy's Artillery; hinders him from raising Shoulderings to secure himself: Besides that, the Breach of the opposite Face is much better defended, and the Field better scowred.

But one would think they might enjoy all these Advantages without possessing the Plat-form of the Bastion; and by that means deprive themselves of the Advantage of making En∣••renchments; which favour the Defence of Assaults. Besides that, these Cavaleers are of no use for the Defence of the Breach made in the Bastions where they stand. And there is this moreover, That the B••sieger may at the same time, with a Mine carry away a part of this Cavaleer with the Face of the Bastion. And lastly, ••Tis for the Defendents to deprive themselves of several Advantages; which we shall observe in the following Method, and which has all the Advantages of the preceding Situations, without being obnoxious to their Imperfections. But before we speak of this Cavaleer, ob∣serve the Construction of it; of which we have set down the Advantages, and Disadvantages.

• 1. If the Bastion is empty, it ought to be fill'd up, till it come to be as high as the Plat-form.
• 2. Which being done, raise that which was empty upon the Plat-form, from 9, to 10 Feet.
• 3. Having levell'd that Heighth toward the Top, you shall draw the B••se of the Parapet of three Fathoms, which ought not to be rais'd above 6 Feet; because the Cannon are not to be placed higher; for that being higher, they would require a Battery to be raised on purpose.

IV.

Lastly, There are others that place the Cavaleer within the Bastion, of •• circular Figure; disposing it thus;

• 1. They pro••ong a Line of Defence in the Body of the Place, till it cut the Radius of the Centre at the Point A.
• 2. They divide the Distance betwe••n this Point A, and th••t of the Gorge B, into two equal pa••ts; as, AC, CB.
• 3. From the Point C, they draw a Circle, which makes the Base of the Cavaleer.
• 4. They raise this Place from 9, to 10 Feet, above the Plat-form of the B••stion.
• 5. They allow this Cavaleer a Parapet Three Fathoms wide, and One high••
• ...

• 6. The best Lining of this Cavaleer, is with Turf; for if it were of Mason's Work, the Bricks and Stones, which will be shattered from it, would annoy those that defend the Rampar••.

It is objected against this, That they do not leave room enough between the Foot of the Cavaleer, and the Parap••t of the Flank, for the free passage of the Men that are to de∣fend the Breach, and to traverse the Guns, which are upon the Flanks of the Bastion, because their Carriages being long, they will take up a great deal of Ground.

But it is answered, That this Cavaleer being distan••, at least 5 Fathoms from the Parapet, this Passage seems to be more than sufficient to communicate between the Rampart, and the Bastion, in respect of the place of the Cannon; and in regard the largeness of the Base of the Cavaleer, may be lessened, if it be found to incommode the Passage, we must confess, there is room enough, not only when the Cannon are mounted upon small Carriages, but that when they are mounted upon their usual Carriages, these Cavaleers bear them above all others.

CHAP. XV. Of Counterscarps.

IT may be s••id, That Counterscarps cut in the Rock, are the best; for, besides the difficulty of opening them, to descend into the Moat, they need no Talus, or Sloaping; as being sufficient to support themselves.

Those that are li••ed, are to be preferr'd before those that are not, by reason of their durance; though it may be fear'd, That the Enemy will make use of that Lin••ng, to secure him∣self, and make a Gallery all alo••g with E••brasures, to play upon those that defend the Moat: But this Reason signifies little; for when a Moat is full of Water•• the Counterscarp ought to be lin'd of necessity; otherwise the Earth being

moistned by the Water, tumbles easily down•• but if the Moat be dry, a Lining is not so absolutely necessary. The Sloaping ought to be allowed after such a manner, That if the Enemy should enter with the Soldiers of the Garrison, upon some hot occasion, he could not easily get out again. That part of the Counterscarp which is before the Point of the Bastion, ought to be rounded, to gain the Space above the Covert-Way; provided you can keep there a Body of your Men, to be in a condition to sustain an Assault.

CHAP. XVI. Of the Streets, Places of Arms, Corps de Guard, and Magazines.

HAving shew'd, Book 3. Chap. XX. how to make the Streets in a Fortress, we shall first speak of the Places of Arms. The Grand Place of Arms ought to be in the middle of the Fort; the construction of which is contained in Chap•• XX. Sect. 3 The lesser Places of Arms ought to be on the side of the Bas••ions; the bigness of which ought to be be proportioned so, as to hold 200 men for every Bastion; or 500, if they are to sustain a Siege: And in regard that every Man marching in Battalia, takes up no more than Three Feet in Rank, and Seven in File, it is easie to know how many Men will serve for every Fortress, and how large the Places of Arms ought to be.

The most numerous Corps de Guard ought to be in those Parts, where the most numerous Guard mounts. There must be one or two Chimneys at least; and a little Theatre of Wood all along, about three Feet high from the ground, and seven or eight Feet broad, for the Soldiers to lie upon. The other Corps de Guard, built after the same manner are to be placed near the Gates, or Passages.

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In regard that there is always Occasion for Ammunition, that is, ••or Powder and ••all, for the Soldiers that are upon the Ramparts, there must be Arsenals near at hand. But great ca••e must be taken to put the Powder where it may not take Wet•• much more, where it may be in danger of being Fired.

The Magazines of Hay and Provender for the Cavalry, ought to be near the Stables where the Horses stand. The others must be built in the most secure Parts of the Garri∣son.

In regard the Soldiers, as well Foot, as Horse, are often lodg'd in Hutts; these Hutts are to be set up near the Ram∣part, to the end, that in case of necessity, they may be ready up∣on the Rampart, to defend the Place. To which purpose, the Town is to furnish them with Beds, Tables, Benches, & Hang∣ings for the Officers Chambers, under whose Government the Soldiers are to serve; their Presence being necessary, to keep them in order, and from being injurious to the People of the Town. Every Hutt ought to be so large as to hold ••our Soldiers. Every Captain ought to have a particular Cham∣ber, and another fo•• two Lieutenants. These Hutts ought to be 18 Fathoms long, and 7 and a half broad; and four Fathoms high; though there are some that are higher.

CHAP. XVII. Of the Gates.

A Gate, if it be well placed, ought to be in the middle of the Curtain; because that in that part it is defended with two Flanks, which lie on both the extremities of it. The Gate cannot be too well secur'd, because that there Sur∣prises are generally most attempted; whether by Petarding or by Intelligence from the Garrison. Some place the Gates in the Flanks, because, say they, the Sallies are by that means more private, and for that those Gates look a thwart

the opposite Flank. But, besides that, being so placed, they very much weaken the Flanks, which are almost the chief strength of the Place, and hinder by that means the opposite Face to that Flank from being well defended; they also hin∣der the use of the retir'd Flanks and the Tenailles.

As for those that are placed in the Faces of the Bastions, they are worse dispos'd; not only because it is a kind of a Breach already made, but because they are not Flank'd, but by a part at a great distance: The Sallies also are too much in view; nor can they be secur'd by any Work, but such a one as is not Flank'd; which is a very great defect.

The Wideness of the Gates ought to be from 14 to 16 Feet. The Height from 15 to 17. The Thickness like to that of the Rampart of the Wall. They ought to be all vaulted, or else the greatest part of them, and well guarded.

There must be great S••ones laid at the Extremities of the Gates to hinder the Carts from spoiling the Wall. The Wood of the Gate ought to be of good Oak, join'd and fasten'd with good Nails and strong Bars of Iron.

CHAP. XVIII. Of Back-Doors, or Sally-Ports, and Draw-Bridges.

TO sally out of the False Brays, Sally-Ports are made of such a wideness that the Cannon may pass through them: that is to say, ••hey ought to be from 7 to 8 Feet wide; and from 8 to 9 Feet high.

The Draw-Bridges are made after several Fashions; but the most usual are made with Plyers. Their Length and their Wideness ought to be proportionable to the Borders or Frame of the Gate which are to hold them, being drawn up. The Arms ought to be from 8 to 9 Inches thick, as also the Beam that joins them.

The Shoulder to which the Arms are annexed, a••d upon which they are to turn, ought to be from 14 to 16 Inches in Diameter. The Extremities ••e••ng bound about with two good Ci••cles of Iron; you must drive through the Cen••re two Iron Pins, a Foot long, and two or three Inches in Diame∣ter, to the end that it may the more ea••ily move upon a strong Band of crooked Iron, which is to be joined to the Thre∣shold and J••umbs, or Side-Posts, of the Gate. The P••y∣ers a••e to be twice the height of the Ga••e, at least, and one Foot in Diameter. The Inner Square must be travers••d with a St. Andrew's Cross, which will serve for a Counter poise. The Chains are to be of Brass, to the end that the Bridge may never be let down without making a noise.

CHAP. XIX. Of Bridges.

THE Bridges of a Town are to be from 14 to 15 Feet wide; lower than the Field•• and somewhat ••ound. When they are streight and even, they ought to be made a little higher in the middle than toward the Extremities, that the f••ot of the Gate may not be discover'd. Though the Supporters of Bridges may be of Stone, nevertheless they will be better, if their Planks and Rayls are of Wood, that they may be the more eas••ly cut down upon occasion. When there is no Half Moon b••fore a Gate, it is certain that the Bridge which crosses the Moat ought to be the wider, because there must be a good Corps de Guard upon it, and a Draw Bridge. B••t i•• there be a Half-Moon, some ••u••n aside the way all along the Gorge of the Half-Moon above the Coun••ersca••p, and make a Co••ps de Guard and a Palisado, which hinders the entrance of the Enemy: Others carry the Way thorough the Extremities of the Face. And a good Corps de Guard ought to be set at the end of the Bridge with a Portcullice.