The English academy, or, A brief introduction to the seven liberal arts grammar, arithmetick, geometrie, musick, astronomie, rhetorick & logic : to which is added the necessary arts and mysteries of navigation, dyaling, surveying, mensuration, gauging & fortification, practically laid down in all their material points and particulars, highly approved to be known by the ingenious, and as such are desirous to profit, or render themselves accomplished : chiefly intended for the instruction of young scholars, who are acquainted with no other than their native language, but may also be very useful to other persons that have made some progress in the studies of the said arts / by John Newton.

Exact Rules and Directions for For∣tification, Regular and Irregular for War, Offensive or Defensive, Outworks and Inward Strengths, &c.

FOrtification is of great moment, and in the well observing and Regular per∣forming it for defence and offence, many times consists the Safety of Countries and Kingdoms, howev••r the Scituation and Circumstances require much Variation, so that to prescribe the Models of all Fortifica∣tions would be Endless, and therefore it will be most convenient to treat of the mo∣dern, or those most generally in use.

Observe then of this kind, your works require to be Flanked to keep the Enemy from a sudden Entrance, where any Breach is made by the great Guns, for if the Be∣siegers have made their approaches so near, that the Besiegeds Cannon in the Front are dismounted, then you may be assured their design is to put their Miners to pass the Ditch, and then if they perceive any place out of sight of the Besiegeds firing, they will have an opportunity to make their

Mines with little difficulty, so that a place unless the Garrison be very Large to make frequent Sallys, may be taken in 8 or 10 days, that with Flankers might hold out much Longer, so that it has been the pra∣ctice of late to turn the Antient Round Ba∣stions into sharp pointed ones, which not only upon occasion serve for Flankers to defend against any hasty approach, but to slaunt and hinder the force of the great Shot playing against the Town or Fort.

Amongst other things necessary on this occasion, the great Line of defence is to be considered, or what may be found near E∣qual into it, viz. the Polygon Interiour, which ought not in mos•• cases to exceed 120 Fathoms, or 720 Feet, and this is found to be a point blank of the Execution of a Mus∣quet, the Cannon being here Incommodi∣ous, and therefore the defence is to be ta∣ken from the former, the latter beside the waste of Ammunition, lying much lyable to be dismounted, and not so easily again re∣mounted, as the Emergency requires, and the difficulty is likewise greater in maintai∣ning a continual Fire, and if the work be not incommoded by their over largeness, the more Capacious, the Gorges and Flanks are, the better will the Fortification be found for defence, for then the Soldiers may pass to and fro in a good front to the Bastion, when Cannon is planted on both

sides the Flank, and give no interruption to those that are at the Flanks, and if there be but a supposed necessity required, there must be a vacancy left for Retrenchments, and a place under the Bastions left fit for Mining, that if it come to extremity when you have drawn off as soon as the Enemy has possessed the Bastion, it may be blown up, & their Attacque cleared till the Besieged may know what is further to be done in the defence of the place, and draw their strengths from other parts thitherwards.

Above all, the Curtain Flanks and Faces of the opposite Bastion are to be well secu∣red and guarded, as likewise the Ditch and Counterscarp being made as large as the due proportion of the Bastion will allow, for if they be too great, their Capitals will be found too long, and thereupon the de∣fence Line exceed the Port of any Musquet, or small piece— and being too little they will become blunt, and so cut off the se∣cond Flank, whilst it ought to be held con∣siderable.

The degrees of the Angle of a Bastion, ought not to be less than 60, or more than 90, some small matter allowed over or under; and the reason is, if it be much under 60, it will be found too slender, or above 90 too large, or more than may be well sup∣plyed; and moreover, by that the second Flank is shortned, and it will be computed

in less Ground than the Bastion, where it is an Angle of less degrees, though built on the like Gorge and Flanks, and observe in all your works to let them be Cannon proof.

If we proceed to a description of Regu∣lar Fortification, it is to be understood of such Models as are equally Angular, and founded upon Equilateral Figures, to be de∣scribed in a Circle, as it may be a Triangle, Quadrangle, or a Quartil Pentagon, or a Figure of 5 sides to a Dodecagon, or a Fi∣gure of 12 sides, and in this case the Basti∣on must be so posited, that all the points may answer in like distance from the Cen∣tre. The Curtains of Equal Length, and all the Angles and Lines to be of an equal Magnitude for Regular Models are to be computed from a Calculation of the Angle at the Centre, and that is done by divi∣ding 360, the number of the degrees that a Circle is usually divided into, and where∣in the Regular Figure is to be described by the number of any Polygons sides, or the Regular Figure, that any Fort or Work of War of this nature is to consist on, for hereby the Quotient demonstrates the An∣gle of the Centre, as may be demonstrated by a Figure of five sides, wherein by o∣peration, the Angle of the Center is cer∣tain to be 72 degrees, and the like of any other figure, then if you draw a Circle with

the Protractor, or Line of Chords, the first being a Semi circle, and the last the fourth part of a Semi-circle, or 90 degrees projected on a straight line, and the Angle beset off at the Center at 72 degrees, the Circle will thereby be divided into 5 equal proportions, or parts, and the straight line drawn to the points, produces a Penta∣gone. Besides this Model of Fortification, there are sundry Outworks required for strengthening a place, they hinder much the Besiegers from making their Lodgments if the ground happen to be low near the Counterscarp, or from suddeinly raising Batteries by the advantage of that ground, if it happen to be high; wherefore a care∣ful Enginier always provides Outworks to hinder it, and prolong the approaches to the main Fort, and these Outworks are various as the Situation of the place, or the danger requires.

Ravelins, being an usual Outwork, they are usually of two kinds, one with lines, and the other wanting; the first of these are placed before long Curtains, where the two Bastions are not capable of Flanking each other within Musquet shot, and the length of the Curtain not sufficient for the erecting a Plate Bastion in its Cen∣ter, and supply the defect of a Bastion by covering and defending, and to erect these kind, the Ditch must be cut parallel with

the Curtain, and above it erect a Capital from 18 to 20 Poles, and let your Demi∣gorges be no more than from 10 to 12 Poles the Flanks, from 8 to 10, the Ditch sur∣rounding them, and the greatness of the Flanks Parallel to the face of the Ravelin till the ditch of the place of the face of the Bastion be met by it, that so the Ravelins Flanks may scowr over all the ditch that faces the Bastion.

The Ravelins without lines, consist only of a Capital and two faces, the Capitals from 12 to 18 Poles the face, edging or drawing nearer to the shoulders of the Ba∣stion, that within the Ravelin may be com∣manded by the Curtain and two Flanks.

The half Moon is a work ever raised be∣fore the Bastions point, being so named from the lowness of its Gorges Cavity, &c. and is to secure the two faces of the Bastion, but when the faces have but a weak defence from the Ravelin, these works are soon made useless, or ruined, and give the Besieged an opportunity of Lodgment, & may serve for Batteries and Flanks against the opposing Bastions, however, they may be retrenched by Traverses, yet they will not fail to at∣tacque entirely in the face, or where you have your last retrenchment, also, that cal∣led the Counterguard runs the like hazard.

The Outworks, called the Hornworks, are placed before the Curtains, a Perpendicular

Line being drawn from it at the two Flanks about 60 pole front, towards the Campaign, their front to be 36 Poles, equal to the Curtain, to be divided into 3 Parts, one of them for the Curtain, and the other for the Demigorges, appertaining to the Hornwork, as for the Flanks, they are to be six Rods, or 72 foot each, and this work is held one of the best and strongest Outworks, if well manned and managed, especially when a Ravelin is placed before it.

The Outworks called the Tenalis, is built to secure the Bridge when it is hard pressed upon their sides, containing 50 Poles, and the Fronts no more than 36, which being divided into 4 equal parts, a Perpendicu∣lar is drawn in the middle, whereon a 1/9 of the front is set off inwards towards the Town, and the Lines must be drawn from the sides, to form the face; this work is advantageous for Counter Approaches, and for receiving succours into the Town.

The Crownwork is usually erected, a when heighth is so near to the place, that a Musquet shot may reach it, and then the sides of the works must be extended before the Bastion, or Curtain about 65 Poles, & the Demibastions point to be about 60 degrees, then the Ex∣tremities of the sides must be joyned, and a Perpendicular Line raised on the middle, on which six, for the Capital, 18 Rods, making an Angle of two Interiour Polygons.

FINIS.