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 V. (Book 5)

CHAP. I.

IN regard that Fortification is either Continual, or Tran∣sitory, we shall now speak of the latter, as having gi∣ven full Instructions for the first: Let us begin with a Redoubt.

Of the Raising a Redoubt.

1. Make a Rectangle Square, each side of which con∣tains from 12 to 20 Fathoms.

2. Within this Square draw the Base of the Rampart thr••e Fathoms large; and that of the Parapet from 9 to 10 Feet. The Height of the Rampart above the Level of the Feild ought to be t••ree Feet; and that of the Parapet above the

Platform of the Rampart, of five, as is usual: or of seven, when there are two Steps or Banquets: though sometimes they raise the Rampart a little higher, as necessity re∣quires.

3. About the Rampart toward the Field draw another Parallel three Feet wide, which is call'd the Berme.

4. About the Berme make a Moat of four fathoms, with a Rounding before the Points of the exteriour Sides: the Depth of the Moat ought to be about eight or ten Feet.

5. The Bridge for entrance into the Redoubt ought to be ten or twelve Feet broad, when you would bring the Cannon into it; otherwise five or six Feet of breadth will suffice. See the Plate Q. Fig. XXVIII. in Chap. 14. Lib. 4.

CHAP. II. Of the Half Redoubt.

1. DRaw a Line of 17 Fathoms, as AB.

2. Make an Isosceles Triangle of 12 Fathoms from the Points AB, as AC, CB, and join AC and CB together.

3. Prolong the Line AB, and place upon the Prolonga∣tion on each side eight Fathoms and three Feet, as AD, BE.

4. All the rest is done, as in the precedent Work. See the Plate R, Fig. XXIX.

CHAP. III. Of the Star-Square.

1. MAke a Square, each side containing 12 Fathoms in length, as ABCD.

2. From the middle of each exterior side, ••••aw a Perpen∣dicular

of two Fathoms, as DEFG; and afterwards draw AB in the Point E, BC in the Point F, DC in the Point G, and DA in the Point H. The rest is done, as in the Redoubt. See Plate R, Fig. XXX.

CHAP. IV. Of the Star-Pentagon.

1. DRaw a Circle of 27 Fathoms, and divide it into five equal parts, with 31 Fathoms 5 Feet, as A, B, C, D, E.

2. Join the Sides together, by streight Lines, and divide each into two equal parts, let fall from the middle of them the Perpendiculars of 5 Fathoms, F, G, H, I, L.

3. Draw from the Points A, B, C, D, E, streight Lines into the Points F, G, H, I, L.

4. The Base of the Rampart is 6 Fathoms. That of the Parapet 2. The Berme 3 Feet. And the Breadth of the Moat 5 Fathoms. See Fig. XXXI. of the Plate R.

CHAP. V. Of the Star-Hexagon.

1. DRaw a Circle of 12 Fathoms, and divide it into 12 equal parts, as ABCDEF.

2. Join these Points together by streight Lines, and divide each into two equal parts, then let fall from the middle a Perpendicular of two Fathoms, as GH, IK, MN.

3. Join these Points with the six first, as in the preceding Works.

4. Draw the Base of the Rampart of three Fathoms: that of the Parapet nine Feet; the Berme three Feet; and the Moat of five Fathoms. See the Plate R, Fig. XXXII.

CHAP. VI. Of the Triangle of Half Bastions.

MAke an equilateral Triangle, of which each side con∣tains 24 Fathoms, as ABC.

2. Prolong the side AB, and place upon the Prolongati∣on 8 Fathoms, as BE. Then also prolong the other side BC, and place upon the Prolongation 8 Fathoms CF. Lastly, Place upon that of the Line CA the same distance, as AG.

3. For the Demi-gorges take the same distance, as BH, CI, and AL, and then raise Perpendiculars upon the Points H, I, L. And for the Flanks a length of four Fathoms HM, IN, and LO. This done, join the Points ME, OG, and NI together, to gain the Faces: and thus you have the Design of your Triangle.

4. The Base of the Rampart takes up three Fathoms and a half. The Base of the Parapet 1 Fathom 4 Feet. The Berme 3 Feet. The Moat 5 Fathoms. It ought to be parallel to the Flanks, and round before the Points of the Half Bastions. See the late R, Fig. XXXIII.

CHAP. VII. Of the Square of the Half Bastions.

1. MAke a Square, each side containing 24 Fathoms, as A, B, C, D

2. Prolong the Line, BA, and upon the Prolongation place 8 Fathoms, as AE: Then make that of the Line AD, of the same distance as DF. This done, prolong also the Line DC of 8 Fathoms, as CG: Then make the latter CB of the same length as BH.

3. For the Demi-Gorges, take also 8 Fathoms, B, M, A, I, D, K, and C, L.

4. Raise upon the Points I, K, L, M, the Flanks perpen∣dicularly, the length of which is 4 Fathoms, as I, O, K, P, L, Q, and M, N.

5. Draw the Faces, joining together NHQGPF, and OE.

6. Having the Draught of the Square, let the rest be as in the preceding Triangle. See the Plate S. Figure 34.

CHAP. VIII. Of the Square of entire Bastions.

1. MAke a Square, each side containing 31 Fathoms, as A, B, C, D.

2. From the middle of each side, let fall a Perpendicular of 4 Fathoms, as E, F, G, H

3. Draw the Faces after Vau••an's manner, and add thereto 10 Fathoms.

4. Take the Extremities of the two Faces; and from one of them, let the Compass fall upon the Complement of the other; and in that part where it touches the Complement, join the same Point to the Extremity of the Face, which is the nearest to it, for the Flank. That done, draw the Curtain.

5. The Base of the Rampart contains 5 Fathoms, that of the Parapet 2 Fathoms 3 Feet. The Berme 3 Feet, and the Breadth of the Moat 6 Fathoms. See the Plate S. Fi∣gure 35.

CHAP. IX. Of a Pentagon with entire Bastions.

1. DRAW a Circle of 17 Fathoms, and divide it into five equal parts, with one distance of 31 Fathoms, •• Feet as A, B, C, D, E; and join the Points together by right Lines.

2. From the middle of each side let fall a Perpendicu∣lar of five Fathoms, and draw the Faces as usually, after Vauban's manner; the length of which must be 10 Fathoms.

3. The Flank is made, by setting the two Points of the Compass upon the •• Extremities of the Faces; of which the one falls upon the Complement of the Line of Defence, as has been said in the preceding Chapter: This done, join the two Flanks together for the Curtain.

4. The Base of the Rampart takes up •• Fathoms. The Base of the Parapet 2 Fathoms 3 Feet.

5. The Berme 3 Feet: The Breadth of the Moat 6 Fa∣thoms. See the Plate S. Figure 36.

CHAP. X. Of the Half-Hexagon with entire Bastions.

1. DRAW a Circle of 28 Fathoms, 4 Feet, and divide it with the same distance into 6 equal parts, of which you shall take three for your Temporary Work.

2. Divide into two equal parts each of the three sides; and from the middle let fall a Perpendicular of 5 Fathoms.

3. Draw the Faces as usually; of which let the length be •• Fathoms.

The Flank and Curtain are made, as in the preceding Works.

5. The Base of the Rampart contains 6 Fathoms. The Base of the Parapet, 2 Fathoms 4 Feet. The Berme 3 Feet. The Breadth of the Moat 6 Fathoms. See the Plate S. Fi∣gure 37.

A Remark.

IN regard this Fortification is only for present use; and be∣cause for that Reason it is sometimes stronger than the other, the Draught and Proportion of it could not be ascertain'd, as in a continual regular Fortification. Only we may say, that most frequently the Rampart of these sorts of Forts is rai∣sed like those of Redoubts. See the first Chapter, Lib. V.

CHAP. XI. Of the Maxims of Irregular Fortification.

IRregular Fortification is that, of which all the Sides and Angles are not equal one to another. The Original of this Fortification proceeds from Ancient Towns and Cities•• which were built after no regular Figure, and yet required to be encompassed with Walls and Bastions, to defend them∣selves against the Assaults of their Enemies. But because it was impossible to fortifie those irregular Places, and make them, in respect of their Duration, equal to regular Places•• there are certain Maxims, according to which they may be environ'd with a passable Fortification. For Example:

• 1. Every irregular Fortification ought to be made accor∣ding to the Maxims of the regular as near as may be.
• 2. The most irregular Forts are the best, provided they be not too ••asie of Access.
• ...

• 3. Entire B••stions are to be preferred as much as may be before Half Bastions.
• 4. No Face ought to exceed 60 Fathoms.
• 5. No Flank ought to be less than 16 Fathoms, if it be possible.

Therefore when you are to make an irregular Fortifica∣tion, you must consider, 1. The Q••••lity of the Situ••tion. 2. The time allowed to make the Work. 3. The num∣ber of Men which are to be put in to defend it. 4. The num∣ber of Workmen. 5. The Victuals. After all you must draw the Plane, and fortifie it after the following manner.

CHAP. XII. The manner of Fortifying an irregular Place, where there is nothing but the Field.

1. HAving the Plane of the irregular Place, divide each ex∣ter or side into two equ••l parts; and from the Middle let fall a Perpendicular••

2. Upon each exterior side draw an ••••osceles Triangle of 480 Fathoms.

3. Place upon these Triangles all the Parts and Distances which you make use of in a regular Fortific••tion, and take the Distances across to put them upon he parts of your irre∣gular Plane•• For Example; if an irregular Pentago•• be ••o be fortified, I take 180 Fathoms an•• I m••ke ••pon each exterior side an ••soscel••s Triangle, ABC. Then I ••ak•• 2•• Fathoms, which I put upon the Triangle ABC, as CDE; of which the length DE, shall be the true Length for the Pe••pendicular of the Line AB: Which done, I put 50 Fathoms upon the same Triangle, as CFG the Length FG, sh••ll be the just dista••ce ••or the Face of my Work. After this, I put again 38 Fathoms 3 Feet upon the Triangle; and the distance taken across HI, will give me the true Length for my Complement of the Line of Defe••ce. Las••ly, I join the Flanks and the Curtains together, as i•• a

[illustration]

The Plan of a Horn work before the Bastion of a Square.

[illustration]

The Draught of a Horn-work with Shoulders.

[illustration]

a Horn-work with a Crown before it.

[illustration]

A draught of a Square with a Crown Work before the Courtin. Fig: 11

[illustration]

A Pentagone or Work of five Bastions. Fig: XVI.

[illustration]

A Draught of a Pen¦tagone or five sided Figure with Tenailles within the Ditch. Fig: 16.

regular. After which I divide the Flank into 3 equal parts; I draw the Brisure as usually, and retain one of the 3 parts of the divided Flank for the Orillon, and the two o∣thers for the hollow Tower. See the Plate T. Fig. 38.

CHAP. XIII. Of the Body of the Placo in an Irregular Fortification.

THE Body of the Place make thus:

• 1. Take 11 Fathoms for the Base of the Rampart, and put them upon each Triangle. The Length a-cross will always give you the true Breadth of the Base of the Ram∣part.
• 2. Take 3 Fathoms, and bring them round about the Place, without putting them upon the Triangles. Draw the Banquets as usually.
• 3. Take 20 Fathoms for the B••eadth of the Moat, and ••ut them upon all the Triangles, the Distance taken a-cross ••ill be the true Breadth of the Moat for every side. The manner of making this Fortification is the same with that ••f the Regular. See the Plate T. Fig. 38.

CHAP. XIV. To make a Half-Moon before these Fortifications.

BE sure to see whether the Length of the ••urtain exceeds 100 fathoms or no. If it be from 100 to 140 Fathoms, 〈◊〉〈◊〉 50 ••athoms for the Capital of the Half-Moon or Rave∣••••••. But if it be larger than 140 Fathoms, erect before 〈◊〉〈◊〉 Ravelin another Work, whether a Horn or Crown-••ork. If the Curtain be not longer than 100 Fathoms, 〈◊〉〈◊〉 the half of the Curtain with the Brisure, for the Capi∣•••••• of the Ravelin, and the rest is done as in a regular For∣tification.

For the Base of the Rampart is 8 Fathoms. That of the Parapet 3. The Breadth of the Moat 12. These Distances are to be put upon the Triangles, before the ex∣terior sides of which you intend to place the Ravelin, and afterwards taken a-cross.

CHAP. XV. To set other exterior Works before the same Fortifications.

IF an exterior Polygon exceeds 120 Fathoms, and that you have still room to erect a good exterior Work be∣fore it, whether Horn or Crown-Work; as you may see in Fig. 39. which is a Crown-Work made according to the Rules of Chap. 10. lib. 3. The parts of it ought all to be mark'd upon the Triangle.

AB, Is the Basis of the Rampart of the Ravelin, and the Horn-work.

CD, Is the Basis of the Rampart of the Body of the Place.

EF, Is the Breadth of the Moat belonging to the Rave∣lin and Horn-work.

GH, Is the Perpendicular of the Horn-work, from the end of which are drawn the Faces.

IK, Is the Breadth of the Moat belonging to the Body of the Place.

23 is the Perpendicular of the Body of the Place.

LM, Is the Face of the Horn-work.

NO, The Complement of the Line of Defence to th•• B••d•• of the Place.

PQ, The Face of the Body of the Place.

RS, The Capital of the Horn-work.

TV, The Distance which joins t••e Point of the Capi•••••• to the Horn-work.

WX, Are the Wings of the Horn-work.

CHAP. XVI. How to fortifie an Irregular Place already built.

TO avoid much Labour, you must fortifie the parts of an Old Fortification, and finish them, in the same manner as they were begun; unless they are gone utter∣ly to decay; and then you may make what alterations you please. To the end therefore, that Money may be laid out to good purpose, when the Flanks are repaired, they must allow an Overture of 100 deg. If the Faces are tolerable, let them alone as they are, to avoid the vast expence•• in making others. Whence it comes to pass, that there is no ancient place which is fortifi'd after the French manner, because the Engineers have been always forc'd to labour upon Dutch Fortifications. As for the Rampart and Parapet, they may be better fortifi'd whatever Face they have. But to come to the Thing it self, let us observe the following Rules:

I••

The exterior Side, the Length of which is from 60 to 80 fathoms, requires a Demi-Gorge from 14 to 15 fathoms, and a Flank of 15 fathoms.

II.

If the exterior Side takes up from 80 to 140 fathoms, it is to be divided into 5 equal parts; of which one is retained for the Demi-Gorge. The Flank changes according to the variety of the Sides. For example, if the exterior Side is of 80 fathoms, the Flank shall be of 16.

• If of 90 the Flank of 17.
• If of 100 the Flank of 18.
• If of 105 the Flank of 19.
• If of 110 the Flank of 20.
• If of 115 the Flank of 21.
• If of 120 the Flank of ••2.
• If of 125 the Flank of 23.
• If of 130 the Flank of 24.
• If of 135 the Flank of 25.
• If of 140 the Flank of 25 Fathoms 3 Feet.

This being well understood, it will not be difficult to reduce it into Practice. Suppose the Pentagon following, of which the Side AB is 130 Fathoms, BC 124, CD 130, DE 113 Fathoms 3 Feet, EA 146 Fathoms, and that you design to Fortifie it.

1. Allow the fifth part of each exterior Side for the Demi-Gorges, as AF, BG, CI, CK, DL, DM, EN, EO, and AP.

2. Raise upon FG, HI, KL, MN, OP, Perpendicu∣lars for the Flanks, in case you cannot allow them an Over∣ture of 100 degrees; the Length of which must be propor∣tionable to the Length of the Sides. For Example: The Flanks FG shall have 24 Fathoms, HI 22, KL 24, MN 20, EA 25 Fathoms and 3 Feet.

3. In drawing the Line of Defence, you will have the Faces at the same time.

4. The Base of the Rampart takes up 11 Fathom••. That of the Parapet 3. The Breadth of the Moat 20 Fathoms. The Covert way, and the Glacis, are made as is usual. See the Plate W. Fig. 40.

Observation.

The Flank is left after the Holland-manner; that is to say, without either Orillon, or hollow Tower, to avoid over∣much Expence.

III.

If the exterior side be from 140, to 170 Fathoms, the Flanks are allowed the following Length;

If it be 145, allow the Flank 25 fathoms, 3 feet.

If 150, to the Flank 26 fathoms.

If 155, to the Flank 26 fathoms, 3 feet.

If 160, to the Flank 27 fathom.

IV.

The exterior Side surpassing the Length of 160 fathoms, to 280, is look'd upon then as if it had two sides; that is to say, that besides the Bastions which are placed upon the Angles, there should be a Plat-form in the middle•• as you see in Fig. 41, where the Side AB is 200 fathoms, and the Construction of it thus;

• 1. Divide the Side AB into two equal parts; as, AC, CB.
• 2. Divide either the Distance AC, or the other CB into five equal parts, to give one of them to the Demigorge; as, AD, EB, CF, CG.
• 3. Raise upon DG, FE, the Flanks of an Overture of 100 deg. the Length of which shall be the Demi-gorge.
• 4. From the Point C, draw the Capital, which takes up the Length of the entire Gorge; as, CH.
• 5. Join the Extremities of the Flanks, and the Point H, together, by a streight Line, to gain the Faces. See the Plate W, Fig 41.

Observation.

These sorts of Bastions are perfectly well defended; for the Flanks of the neighbouring Bastions play backwards upon their Faces; besides that, almost all the Curtain serves them instead of a second Flank, and very much augments their Defence.

V.

The Exterior Side surpassing 280 Fathoms, two flat Basti∣ons are placed there; holding this for a Maxim that the greatest Side ought to be 140 fathoms.

CHAP. XVII. How to Fortifie an Acute Angle.

IF you find by chance an Acute Angle with the Circuit of a Place which is to be fortified, since it is impossible to repair this defect, because you are obliged to make use of the old Ramparts; you are only to put upon this Angle a Tenaille-B••∣••tion; which is thus erected;

• 1. Having made the Flanks, draw the Faces as the Line of Defence requires; but in regard they would be excessive long, and would form too acute a Point, that is corrected by putting 40 fathoms from the top of the F••ank above the Face; as, AB, CD.
• 2. Join BD together by a right Line, and then divide that Line into two equal Parts, BE, ED; and from the middle of the same Line, let fall a Perpendicular, which has for its Length the third part of the same Line; as, EF.
• 3. Draw the Points BD, in the Point F, by right Lines, and your Bastion is made. Oft times they erect little Rave∣lins before th••se sorts of Bastions: But to say the Truth, this Work is not worth any thing; nor is it ever to be made use of, but upon necessity. But you shall meet with it in some Places; as, at Geneva, and Charlemont. This small Ravelin must not be separated from the B••stion, but by a small Moat of five or six fathoms. Moreover, there is no necessity for its having Ramparts, but only a good Parapet Cannon proof. There are several other Ways of fortifying an acute Angle; but which are of no more value than this. Therefore we must endeavour to avoid them; for no••withstanding all the care a Man can take to fortifie this Angle, it will be very defective. See the Plate W. Fig. 42.

CHAP. XVIII. How to fortifie a Re-entring Angle.

THere are few irregular Places, of which the old Enclo∣sure does not form a re-entring Angle; which is almost always secure, as being seen from several parts. But usually it is accompanied with one defect, that it al∣most always forms the two ••aliant Angles which are next it, too acute. 'Tis true, that if these saliant Angles were not too acute, your Firing-place would be very great, from •• Work made upon the Re-entring Angle, to defend the Ba∣stions that are in sight of it; nor is it always a Fault to have these re-entring Angles, which are thus fortified.

If the Angle be not very far sunk in, and very obtuse, as A, it is thus to be fortified;

1. Place on each Side the Angle great Demi-Gorges, in case the Sides will permit it, and raise perpendicular Flanks, as large as you can.

2. Join their Extremities together, by a right Line; which you shall divide into two equal parts; and from the middle raise a Perpendicular, containing the Moiety of the said Line.

3. Draw the Extremities of the Flanks toward the Capital Line of that Perpendicular, and your re-entring Angle will be fortified. See Plate X. Fig. 43.

If the re-entri••g A••gle be somewhat obtuse, or streight, in this Case, having taken good Demi-Gorges from every side of the Angle, the Flanks are there to be rais'd; the meeting of which, forms the Salian•• Angle B; which is capable to de∣fend the neighbouring B••stions. Se•• Plate ••o. Fig. 44.

CHAP. XIX. Of the Artillery.

HAving given some account of Irregular Fortificaion, reser∣ving to our selves another Time to speak more of it; we shall only observe what sort of Artillery they have in France. There is 1. The Cannon, which is call'd the Battering Piece. 2. The Colverin. 3. The Falcon 4. The Sak••r. 5. The Petard. 6. The Small Petard. The Battering Piece is 10 Feet long, The Bullet about six Inches Diameter, and weighs 33 pounds. requiring two pounds of Powder at least, to charge it; and it carries directly forward 360 Fathoms. At the distance of 100 Fathoms, it pierces two Fathoms of clos'd Earth. If it be not well setled, it pierces two fathoms and a half; and if the Earth be poor, and hungry, it pierces four fathoms, You may discharge it eighty times in a day. The Dutch Can∣non slings a Bullet of 48 pounds, 400 feet distance, and pierces a Rampart of good and well clos'd Earth 20 feet deep. A half Piece of Battery carries a Bullet of 24 pounds, at 300 feet di∣stance, and enters twelve feet of good Earth. The Falcon carries a twelve pounder 200 feet off, and enters 7 feet into a good Parapet.

A Small Petard cannot break a double Gate well barr'd.

A Great Petard, fix'd to a weak Gate, usually makes no more than a Hole; and the greatest Execution it can produce, is to break the fore part of it.

There is nothing can stop the Execution of Mines, as they make them at present; nevertheless there must be a Propor∣tion between the Petards, the Mines, &c. and the Powder.

Lastly, A Musquet carries 120 Fathoms, and if double charged 150, though it will kill a Man above 300 Paces. Discharg'd very near it will pierce two Planks two Fingers thick: but discharg'd at 50 Paces, it enters according to the substance of the Body it meets with. We shall insist no longer on these things at this time; intending to speak more amply of them in another Treatise, where we shall shew the manner how to attack a Place.

THE END.