The Uses of the aforesaid Instruments, applied to the Fortification of Places.

• The Line AB, is called the exterior Side of the Polygon, and LM the interior Side thereof.
• LG the Demi-gorge of the Bastion, of which EG is the Flank, AE the Face, and AL the Capital.
• GH is the Courtain, and AH the Line of Defence Razant.
• The Figure ALGE represents a Demi-Bastion.
• The Angle ANB is the Angle of the Center.
• The Angle KAB is the Angle of the Polygon.
• The Angle IAE, made by the two Faces, is the flanquant Angle, or Angle of the Bastion.
• The Angle AEG made by the Face and the Flank, is called the Angle of the Shoulder.
• The Angle EGH, made by the Flank and the Courtain, is called the Angle of the Flank.
• The Angle EGB, made by the Flank and the Line of Defence, is called the interior flanquant Angle.
• The Angle EDF, made by the two Razant Lines intersecting one another towards the Middle of the Courtain, is called the exterior flanquant Angle, or Angle of the Tenaille.
• The Angle EHG, made by the Courtain and Line of Defence Razant, is called the diminished Angle, which is always equal to that made by the Face of the Bastion and the Base, or exterior Side.

Let it be, for Example, an Hexagon: first draw the Line AB 180 Toises, for the exterior Side of the Hexagon, and raise the Perpendicular CD from the Point C of 30 Toises, then draw the Lines ADH, BDG, intersecting each other in the Point D, and take 55 Toises from your Scale, to determine the Length of the Faces AE, BF: from the Point E draw the Flank EG, making a right Angle in the Point G, at the End of the Line of Defence BG, and likewise the other Flank FH at right Angles to AH: finally, draw the Courtain GPI, and you will have one Side of the Hexagon fortified. The other Sides are fortified in the same manner. About this Side of the Polygon thus fortified, you must draw a Ditch, represented by the Lines AC, CB, parallel to the Faces of the Bastions, meeting each other towards the Middle of the Courtain in the Point C. This Ditch ought to be 20 Toises in Breadth, and 3 Toises deep. The Ground taken out in making of the Ditch, serves to form the Rampart with it’s Parapet, and the Glacis of the Covered Way, preserving the finest for the Parapet of the Body of the Place, and the Covered Way; for if the Ground be stony, Cannon-Balls, coming from the Besiegers against Parapets made with it, will make the Stones fly about, and annoy the Soldiers defending the Body of the Place. On the contrary, when the Ground is fine, the Bullets will but make Holes, and enter therein, provided Parapets have Breadth enough to deaden them: by Experience it is found, that Parapets must consist of well-rammed Earth at least 20 Foot thick, to be Proof against Cannon.

The Parapet is made upon the Rampart 24 Feet broad, containing the Banquette, or little Bank, made parallel to the Faces, Flanks, and Courtains, forming the Inclosure of the Place.

The Base of the Rampart is 15 Toises broad, and is made parallel to the Courtains only, to the End that the Bastions may be full, and that there may be there found Earth in case of need, to make an Intrenchment.

When any Bastion is left open, a Mine must be made therein well arched, Bomb proof, and covered with Ground well rammed, and it must be endeavoured to be made so that the Rain-Water cannot get into it, to the End that Provisions put therein, may be preserved from time to time.

The Covered Way is made parallel without the Ditch, about 5 Toises broad, and upon it there is a Parapet made 6 Foot high, and a Banquette, at the Foot of the said Parapet, 3 Foot broad, and a Foot and a half high, so that Soldiers may commodiously use their Arms on the Top of the Parapet, whose Top must be sloped, that is, having a Descent or Slope going down 20 or 30 Toises into the Country.

There must be no hollow Places about this Slope, for the Enemy to cover themselves in; therefore when an Engineer visits the Fortification of a Place, it is requisite for him to examine the adjacent Parts, and have the hollow Places filled up, at least within the reach of a Musquet-shot from the Covered Way; and also to have all Places too high levelled, that so those which defend the Place, may discover all the adjacent Parts.

Draw the indefinite Line ON, representing the Level of the Country, and take 15 Toises, which lay off from O to Q, for denoting the Base of the Rampart; then lay off 20 Toises from O to R, for the Breadth of the Ditch, over-against one of the Faces of the Bastion, for it is wider over-against the Courtain: lay off 5 Toises from R to P, for the Breadth of the Covered Way; and lastly, 20 or 30 Toises from P to N, for the Base of the Glacis. Note, The longer the Base of the Glacis is made, the better will it be.

After having determined the Breadths or Thicknesses; the Heights above the Level of the Country, and Depths below, must be as follows.

Take 3 Toises from your Scale, and raise from the Points O, Q, Perpendiculars of that Height, for raising above the Level of the Country the Platform of the Rampart, whereof OS is the interior Talud, or Slope, going up from the City to the Platform of the Rampart ST; which Platform ought to be 6 or 7 Toises broad, that so Cannon may be commodiously used thereon, as also the other necessary Munitions for the Defence of the Place.

Note, The Rising of the Rampart ought to be very easy over-against the Gorge of the Bastions, for Coaches to go easily there up and down it.

The Base of the Talud OZ, is made with new-dug Earth, equal to the Height all along the Courtains; as if the Height be 3 Toises, the Base of the Slope must be also 3 Toises.

But at the Entry of the Bastions, the Base must be at least twice the Height; that is, if the Height of the Slope be 3 Toises, the Base of it must be at least 6 or 8 Toises, for Coaches to go up it.

When the Rampart is formed, and the Earth sufficiently raised upon it, which cannot be done but with Time and Precaution, in well ramming it every 2 Feet in Height, and laying Fascines to keep it together; a Parapet is made upon the Earth of the Rampart, 6 Feet of interior Height, and 4 Feet of exterior Height (for the Top of the Earth to have a Declivity), to discover any thing beyond the Ditch, and being mounted upon the Banquette, the Covered Way may be seen, and defended in case of Need.

The Base of the Parapet XY, ought to be about 4 Toises broad, to the End that the Top thereof may be at least 20 Feet broad. At the Bottom of the interior Slope of the Parapet, there is made a little Bank 3 Feet wide, and a Foot and a half high, so that the Parapet will be 4\(\frac{1}{2}\) Feet above the Bank, which is sufficient for Soldiers to use their Fire-Arms on the Top thereof.

Care must be taken to lay Beds of Fascines every Foot in height, between the Earth of the Parapet; and in order to keep the Earth of the said Parapet from crumbling, it is covered with Grass-Turfs, cut with a Turfing-Iron, from some neighbouring Common, about 15 Inches long, and 10 broad.

Now to lay these Turfs, you must place the first Bed, or Row of them, very level all along the Distance of several Toises, and then lay the Turfs of the second Bed so, that the Joints of the first may be covered with them, and the Joints of the second likewise covered with the Joints of the third, &c. that so they may all make a good joining.

It is sufficient to give 2 Inches of Declivity to one Foot in height, for the interior Slope; and about 4 Inches to one Foot in height, for the exterior Slope of the Parapet. Note, There ought to be Gardiners to cut and lay the Turfs.

At the Foot of the exterior Slope of the Parapet and the Rampart, there is left a little Berm (marked Q, about 4 Feet wide, for retaining the loose Ground falling down from the Slope.

QB represents the inward Slope of the Ditch, which is 3 Toises deep, and BK is the exterior Slope. If the Ground be brittle, they must have more Slope given them, for hindering it’s falling to the Bottom of the Ditch. The Line KP represents the Platform of the Covered Way, which must be 5 Toises broad. PA represents the Parapet of the Covered Way, with it's Banquette at the Foot thereof. The whole must be 6 Feet high, for covering those which are on the Covered Way.

The superior Slope of the Slope AN, ought to be made of fine Earth, the Stones in which, if there be any, must be taken away with an Iron Rake, and buried at the Foot of the Slope, so that Cannon Balls shot from the Enemy upon the Covered Way, may enter therein, without making the broken Pieces of the Stones fly about upon the Covered Way.

Let, for Example, the Plan of the first Figure be proposed to be drawn upon the Ground.

Instead of a Scale and Compasses, there must be used Staffs, the Toise, and Lines; therefore, after having well examined the Ground, and considered where the Gates and Bastions must be made, which are commonly in the Middle of the Courtains, long Staffs must first be placed, where the flanquant Angles of the Bastions are intended to be.

Now having planted a long Staff upright, in the Place fixed on for the Point of the Bastion (marked A), measure very exactly, with a Toise, or Chain, 90 Toises; at the End of which plant a Staff (marked C): from the Point C continue that Line 90 Toises more; at the End of which plant another Staff, which will be the Point of the Bastion B. In the mean time you are measuring with Chains or Lines, some Workmen must follow, and make a little Trench from Staff to Staff, before the Lines are taken away.

After which, a Perpendicular must be drawn from the Staff C, to the Track ACB.

To draw the said Perpendicular, measure two or three Toises from C to A, where plant a Staff; measure likewise from C towards B an equal Number of Toises, at the End of which plant a second Staff: Take two Lines very equal, and having made Loops in the two Ends of each of them, put those Loops about each of the Staffs, and holding the two other Ends of the Lines in your Hands, stretch them ’till they join upon the Ground, and in their point of Junction plant a third Staff. Lastly, Fasten a Line tight to the Point C, and that third Staff, by which make a Track, which will be perpendicular to the Line ACB.

Measure 30 Toises from the Point C along the Track, at the End of which plant another Staff very upright, which will shew the Point D of the Plan. Return to the Staff A, from which to the Staff D make a Track; along which from the Point A measure 55 Toises towards D, for the Face of the Bastion AE; plant a Staff in the Point E, for denoting the Angle de l’Epaule.

Go to the Point B, and there make the same Operations for drawing the Face BF, and plant a Staff at the Angle de l’Epaule F.

Produce BF from D, towards G; and also AE from D towards H; then measure with the Scale of the Plane the Lines DG, DH, and lay off their Lengths on the Ground from D to G, and from G to H, where plant Staffs: After which it will be easy to draw the Flanks EG, FH, and the Courtain GH.

By this means you will have one Front of a fortified Place, drawn on the Ground; the others may be drawn in the same manner by Staffs and Lines.

Note, It will not be improper to examine with a Semi-Circle, or other such Instrument, whether the Angles drawn upon the Ground are equal to those taken off of the Plane, and to rectify them before the Works are begun.

Care must likewise from time to time be taken, that the Tracks are followed; for without these Precautions there will sometimes happen great Deformities.

These kind of Works are commonly made before the Courtains, and because the Expence in making them is greater than the Expence in making the Ravelins, they are not made without absolute necessity; they serve to cover some Side of the Place, weaker than the others; they likewise serve to occupy an Height, which cannot be done by Persons inclosed in the Body of the Place.

Now to draw a Hornwork, first raise the Indefinite Perpendicular 1, 2, on the Middle of the Courtain; and to this Line draw two Parallels 3, 4, and 5, 6, from the Angles of the Shoulders. These two Parallels, which are called the Wings of the Hornwork, ought to draw their defence from the Faces of the Bastions; whence their Length ought not much to exceed 120 Toises, counting from the Shoulders. Thro’ the Ends of the Wings draw the Line 4, 6, which will be the exterior Side of the Hornwork, and is divided into two equal Parts in the Point 7, by the Perpendicular 1, 2; then take half that exterior Side in your Compasses, and lay it off upon the Sides, from 4 to 8, and from 6 to 9; draw the Lines 4, 9, and 6, 8, which intersecting one another in the Point 10, will form the Angle of the Tenaille, that represents a Work called the Simple Tenaille, which is common enough made before the Courtains, with a little Ravelin without the Ditch, between the two Saliant Angles, and over-against the Middle of the Rentrant Angle.

But to to strengthen this Work, there is added thereto two Demi-bastions, and a Courtain between them; which is better than two simple Rentrant Angles.

To draw the Demi-bastions, bisect the Line 4, 10, in the Point 11; and likewise the Line 10, 6, in the Point 12; then from the Points 11 and 12, draw to the Middle of the Courtain of the Place, as at the Point 1, the occult Lines 121, 111, by which means will be had the little Courtain 1314 of the Hornwork, the two Flanks 1113, 1214, and the two Faces 114, 126.

The Sides of these Works, which are next to the Country (as the Demi-bastions, the Courtain, and the Wings of the Hornwork are), ought to be furnished with a good Parapet of fine Earth well rammed, 18 or 20 Feet thick, and 6 Feet high before, containing a Banquette, like that in the Body of a Place; observing at all times, that the Parapets of the "Works nigher the Center of the Place, must be higher above the Level of the Country, than those Works more distant; to the End that when the Besiegers have made themselves Masters of some Outwork, the Besieged, defending the Body of the Place, seeing them altogether uncovered, may dislodge them therefrom.

These Parapets ought to be sustained by a Rampart, whose Platform having a Banquette, is three or four Toises wide; but when Earth is wanting, we must be content to make several little Banks upon one another eighteen Inches high, and three or four Feet broad; and the Parapet ought to be about 4\(\frac{1}{2}\) Feet above the highest Bank, for covering the Soldiers: the Top of the Parapet must be sloped, gradually descending towards the Country, so that the Besieged may see the Enemy.

The parts of those Works, which are next the Place, must be without a Parapet, and only inclosed with a single Wall, or a Row of Palisadoes, to avoid the Surprizes of the Enemy. It is on this side that a Gate must be (for a Communication from the Works to the Body of the Place); as also a Guard-House, for covering the Soldiers designed for it’s defence.

All these Works ought to be environed with a Ditch 10 or 12 Toises broad, communicating with the Ditch of the Body of the Place, and also as deep.

On the outside of that Ditch is made a Covered Way five or six Toises broad, with a Parapet, and it’s Bank, commonly furnished with an enclosure of strong Palisadoes, drove 4 or 5 Feet into the Ground. The Top of that Parapet must be sloped next to the Country, and if it can be produced 20 or 30 Toises it will be better: for a Slope (or Glacis) cannot be too long; because, by means thereof, the Enemy cannot approach the Body of the Place, without being discovered.

The Outworks of which we have spoken, are the most common ones: There are many other sorts of them, which we shall not mention, it requiring a great Volume.