FOR ( S69 ) FOR

t-oises, from the center of the figure tothe middle of which lie supposes a per-pendicular to be drawn, and to be

divided into n- fl parts (n being thenumber of the sides), two of which heallows for each of the demi-gorges, andthree for each of the capitals, from theouter extremities of which last, rasantlines of defence, drawn to the extre-mities of the demi-gorges or curtain,determine the lengths of the flanks,which are on right lines, drawn fromthe center of the figure, and the posi-tions and lengths of the faces of thebastions.

Mr. Muller has also delivered fourmethods of construction. In the firsthe constructs inwards from an exteriorside of 180 toises, and as the perpen-dicular is altogether undetermined) hesays, it may be taken of any length, asthe 6th, 5th, or 4th part of the side,according to the expense or importanceof the place; but supposes it to beequal to a sixth, or to 31 toises, as inVauban ’s mean fortification, in his firstmethod. He makes the face of thebastion equal to of the exterior side.From Vauban ’s, indeed, it differs in butfew particulars as to the body of theplace.

In 1751, Charles Bisset , who was anengineer extraordinary in the brigade ofengineers that served with the Duke ofCumberland in the Netherlands , andwas present during the siege of Bergen- op-zoom by Marshal Lowendal,publisheda Treatise on the Theory and Construc-tion of Fortification, in which there aremany sensible and judicious remarks.In it he delivers not less than ninemethods, without describing particularlythe lineal constructions of their differentparts. The principal circumstances ofconstruction, however, common to all,or most of them, are the following.

1st. He makes the straight flank of thebastion, in each of them, perpendicularto the line of defence, in imitation ofCount Pagan .

2dly. In each flank he makes both theconvex and concave portion thereof anarch of 60', having for its chord half thestraight flank.

3dly. He allows 15 toises only for thebreadth of the great ditch at the salientangles, whether it be wet or dry.

4thly. He places the interior lines ofthe demi-gorges of the redoubts in the

ravelins on right lines, joining the epaulesof the bastion and “ the salient anglesof the counterscarp of the great ditchor, to speak perhaps more correctly, onright lines drawn frpm the epaulesthrough the extremities of the roundingor circular parts of the great ditch infront of the flanked angles.

5thly. He makes the face of theravelin produced meet the face of thebastion 3 or 4 toises from the epaule orshoulder, except in the eighth method,in which he makes it meet the face at thedistance of 10 toises from the shoulder.

Lastly. In all these methods he pro-poses to give the wall of the ramparta slope equal to one third part of itsperpendicular height, in order to savemasonry and expense.

In 1755 an anonymous writer pub-lished an essay or dissertation entituled“ Essai sur la Fortification , ou F.camendes Causes de la grande Sup'eriorite deVAttaque sur la Defense ;

Des Moyens de determiner la Dis-position et la Construction des Outragespar les Operations de I’Attaque;

Des Changemens que cctte Observationproduiroit dans la Methods de fortifier ;

Des Avantages qui en resulteraientpour la Defense .”

After observing, that all the operationsto which the efforts of the besieged onone side, and the labours of the besiegerson the other,may be reduced, are, in thefirst place, to defend the country to acertain distance round the place, and tohinder the besiegers from approachingit, and constructing their batteries : se-condly, to defend the border of the ditch,and to prevent the besiegers from esta-blishing themselves there, or extendingthemselves along it; thirdly, to defendthe passage of the same ditch, and tohinder the besiegers from attacking thebody of the place; and, lastly, to defendthe breach, and to prevent the besiegersfrom making a lodgement in it and ren-dering themselves masters of the town,he considers the attack of a place forti-fied according to the method of Marsha!de Vauban, and proposes some improve-ments.

An anonymous writer in the Sardinianservice proposes two new methods offortification, in a work entituled Sciencede la Guerre, which was published atTurin in 1744. He discusses, a consi-derable length, the art of fortification ingeneral, its utility, tlie different science*