FORTIFICATION. 



that line ; yet in such very spacious de- 

 fences as crown-works sometimes are, 

 (for their area is occasionally equal to a 

 third of that within the interior line 

 of the polygon,) some exceptions will 

 take place; especially when the rave- 

 lines opposite to the faces of the crown- 

 work are defended by still farther ad- 

 vanced out-works : then the angle of de- 

 filement would be so acute, from the 

 terre-pleine,or horizon, as to cause scarce 

 any difference between the heights of 

 the ravelines and of the bastions of the 

 crown-work ; a matter of obvious im- 

 propriety. Hence it is often necessary 

 to give the ramparts of a crown-work 

 rather more height than the line of de- 

 filement might allow ; raising the rave- 

 line and its entrenchments suitably, and 

 making cavaliers, as instanced in the 

 bastion C, of the crown-work, on the 

 solid bastions 3 and 4, so as to command 

 the whole of the crown-work completely. 

 A moineau, or flat bastion, of similar 

 height with the cavaliers, may be made 

 in the centre of the curtain u T>, for the 

 same purpose. 



Cavaliers are of singular use on many 

 other occasions, to which their form 

 should be accommodated : that in the 

 bastion c of the crown- work is, from 

 its shape, termed, a horseshoe ; the flat- 

 ness of its front is applicable to the situa- 

 tion it there holds, because it opposes 

 a direct fire towards the point 4> ; but 

 its circular tendency gives its front a 

 bias towards the inner parts of the faces 

 of the ravelines, while its flanks pre- 

 sent a direct fire into the ravelines 

 themselves, and give an oblique fire 

 into the opposite ditches, whereby the 

 assault of breaches in the salient angles 

 of the demibastions b b y would become 

 very hazardous. 



The proportions of a crown-work 

 must depend greatly on the purposes 

 for which it is erected, but, whatever 

 be its object, the whole of its defences 

 should be commanded by the works of 

 the principal in so complete a manner, 

 that no part whatever should offer an 

 nsylum to the enemy after carrying it ; 

 and consequently that none of its bat- 

 teries should be able to play into any 

 other of the defences. For the loss of 

 so large a limb, and of the many ser- 

 viceable cannon, platforms, &c. which 

 in such case, are invariably and actively 

 employed against the body of the place, 

 is a very serious concern, and requires 

 the wtmost exertion to oppose even for 

 a time. On this account it is highly 



necessary to have mines under all those 

 parts which can prove serviceable in the 

 smallest degree to the enemy, and to 

 blow them up, whenever a favourable 

 moment may present itself. 



From what has been stated as to the 

 purposes pof crown works, it will be 

 seen by reference to that laid down in 

 the plate, that much attention is re- 

 quisite to give them every defensive 

 property, while on the other hand they 

 should prove of little value to a success- 

 ful assailant. The only work in our 

 plan affected by such a circumstance 

 would be, that the counterguard 7 would 

 be untenable as a battery, though it 

 might retain some small utility as a 

 casement. But by mining all the inner 

 part of the flank, which commands the 

 counterguard, even that evil would be 

 lessened : if, however, an enemy should 

 be able to carry the raveline N, and to 

 maintain his ground therein, notwith- 

 standing the tremendous fires from the 

 faces of the bastions 3 and 4, and from 

 the curtain u v, (all of them direct) but 

 little hope could remain of a success- 

 ful resistance, and the counterguard 

 would be, comparatively, no sacrifice. 

 We, however, see from this, that a 

 tenaille on the lines of defence, t, it, iv* 

 as shewn at P, between the bastions 2 

 and 3, must prove highly serviceable, 

 especially if mounting such heavy metal 

 as would destroy any works thrown up 

 in the raveline N. 



The entrenchments,//, cut the ram- 

 parts of the flanks of the crown-work 

 through all but the revetement, and 

 they are carried as far forward as pos- 

 sible, so as barely to be flanked by a 

 barbet battery in the salient angle of the 

 raveline, that the bastions of the crown- 

 work may be perfectly commanded by 

 musquetry. The cavalier in C, is sup- 

 posed to be mined and destroyed, else 

 it would prove very disadvantageous to 

 the defence of the raveline, which it 

 would partly command. 



We have already observed, that many 

 out- works might be shewn, in addition 

 to those given to the faces of the crown- 

 work, such as lunettes, tenailles, te- 

 naillons, fleches, advanced lunettes, re- 

 doubts, bonnets, &c. but we apprehend 

 the reader will, from the foregoing de- 

 tails, and the plate to which they refer, 

 be able to supply to his imagination the 

 almost endless continuation of outworks, 

 which the limits we are compelled to 

 draw around this branch of science pre- 

 clude us from enlarging upon. 



