covert-way, which they occasion, whilst the covert-way opposite this opening would also be much exposed. The sally ports are to be placed in the faces of the re-entering places of arms, and in the branches of the covert-way of the ravelins between the second and third traverses, as these situations will allow the sallies to be effectually protected in their retreat by the saliants of the covert-way of both the bastions and ravelins. Besides the sally-ports will be better secured than if they were in the saliant places of arms, or near them. In those parts of the fortifications where a road d is made across the glacis, in order to communicate with the country, it is commonly placed between the traverse of a re-entering place of arms (on the side towards the ravelin) and the contiguous traverse of the covert-way of the ravelin. The road is made winding, and from eighteen to twenty or twentyone feet are generally allowed for its breadth, the profile of the glacis on each side being supported by a wall.

Supposing a to be the middle of that end of the sally-port (fig. 2, plate VI.), which is in the direction of the crest of the glacis, erect at 4, the perpendicular ab to that crest, and make it equal to eighteen feet, or any other dimension which the requisite length of the sally-port, according to the greater or smaller elevation of the glacis above the covert-way, may render necessary. Set off one toise from a to b, as well as from a to c, for the breadth of the sally-port, and from c and b as centres, with eb as a radius, describe arcs, cutting each other in e; then frome describe the arc c b. Make cf equal to the base of the interior slope of the glacis, or a little longer, and describe from f and b as centres, with fb as a radius, arcs intersecting at g, from which point, as a centre, the arc fb is to be described. In respect to the other profile of the sally-port, make d h equal to ad, and erect the perpendicular hi of the same length as a b. Next, from d and i as centres, with di as a radius, describe arcs intersecting at m, and m describe the arc di; set off the length of cf from d to n, and from n and i as centres, with ni as a radius, describe arcs cutting each other in o; then from o as a centre, describe the arc ni.

On the subject of the communications of this system, an able commentator upon it, colonel de Malortie, observes, the gates should as much as possible be placed on the least exposed fronts, as this situation will not only render them more secure, but allow sallies to be conveniently made, consisting either of cavalry or infantry, in order to attack in flank and in reverse the besieger's approaches towards some of the other fronts; and, whenever fronts having gates are liable to be attacked, it is proper that they should be flanked by works inaccessible to the besieger. Those parts of the principal roads leading to the gates, which are beyond the glacis, should also be enfiladed by the artillery of the place, so that they may not serve for any purposes useful to the enemy.

The gates nearest to the town are those which belong to the body of the place, and lead to the bridges constructed across the principal ditch, in order to gain the gorges of the redoubts in the

opposite ravelins. These gates should be placed in the middle of the curtains, this part of the fortification being the best covered, and the least exposed to be breached; and they have a bombproof archway, which, at the exterior opening, is twelve feet high in the clear, or a little more, and about ten feet broad; wider spaces are contrived inside of it, from distance to distance, where people on foot may retire when any carriage happens to pass. The exterior of the entrances into the gateways generally has ornaments of masonry, but the architecture should be simple, as any superfluous decorations would augment the expense, without answering any useful purpose; and it is also to be observed, that the masonry should not be carried up higher than the top of the parapet, since, otherwise, it would become a mark for the besieger's artillery: nor should any buildings be coustructed over the archway, although this has been formerly done.

In respect to the standing bridges they may be constructed wholly with stone, when the fronts where they are situated are neither liable to be attacked, or much exposed to the effect of the besieger's shells; provision should, however, be made, in two of the central piles, for placing a few mines to blow up the bridge, if, on account of any unexpected circumstances, it should become instantly necessary to destroy the communication. But it is preferable, under all suppositions, that the bridges should be so contrived as to allow them to be speedily taken to pieces, without encumbering the ditch with rubbish. In consequence, the upper part of the bridges should consist of timber, and be supported by piles of masonry fifteen feet distant from each other, from centre to centre. The length of the draw-bridges is in general twelve feet, and their breadth eleven feet.

From the redoubt of the ravelin, a gate constructed in one of its faces, with a bridge across the ditch in front, leads to the terreplein of the opposite face of the ravelin; whence another gate, also preceded by a bridge which is thrown across the ditch of the ravelin, serves to communicate with the covert-way, and from this work with the road cut through the glacis. But neither of these gateways is arched over, and each consists of an uncovered passage made through the rampart, the profile on each side being supported by a wall in which recesses are contrived for the security of people on foot, if any carriage should happen to pass.

The proper situations for the ramps depend on the nature of the works, and the localities; th are generally placed in the middle of the crtains at the gorges of cavaliers and full bastions, in the flanks and faces of empty bastions, in the faces of out-works, in barbet batteries, &c. In short, wherever this kind of communication may be usefully employed.

The arrangement of the posterns of each front is as follows: there is a postern underneath the curtain, which serves to communicate from the place with the principal ditch; and, when this ditch is dry, another postern is made under the tenaille, leading to the aponier in front The communication from the redoubt of the ravelin

with its own ditch takes place by means of a postern situated under each flank, near the angle of the shoulder; and the redoubts of the re-entering places of arms have each two posterns forming the communication from the redoubt with its ditch.

Before explaining the usual distribution of the pas de souris, it is necessary that the following remarks, relating to the ditches and other objects should be premised.

When the principal ditch contains water, or is dry but very deep, a smaller depth is allowed to the ditch of the ravelin, as in both circumstances this ditch will be better seen from the faces of the bastions which flank it, and therefore more effectually defended; whilst, if the principal ditch is wet, that of the ravelin will be kept dry, which is another advantage.

The ditch of the redoubt in the ravelin is made less deep than that of the ravelin, so as to impede the besieger in his attempt to penetrate into it from the principal ditch, after gaining this ditch through that of the ravelin, in order to cut off the troops which defend the ravelin. And, as a further precaution for the security of these troops in their retreat, the ditch of the redoubt is sunk a little deeper opposite the flanks than along the faces, besides being covered by halfcaponiers U, which, in addition to the coupures X in the ravelin, deprive the besieger of the means of plunging his fire, from the terreplein of the ravelin, into those parts of the ditch of the redoubt where the posterns are placed. Another advantage that is derived from allowing a smaller depth to this ditch than to the ditch of the ravelin, is to render more effectual the flanking defence which it receives from the faces of the

bastions.

The ditch of the redoubts in the re-entering places of arms is still less deep than that of the redoubt in the ravelin, by which means its flank ing defence from the bastion on one side, and the ravelin on the other, is improved. It has no communication with the ditch of the ravelin, so that the besieger cannot penetrate into it from this ditch. The manner in which the pas de souris are generally distributed shall now be explained.

A double pas de souris is placed in the middle of the gorge of the tenaille, in order to mount upon its terreplein, and there is a double one also at the gorge of the redoubt of the ravelin, which serves to get up to the plane of site, whence the terreplein of this redoubt is mounted upon by means of ramps. A single pas de souris leads from the main ditch to that part of the ditch of the redoubt in the ravelin which is opposite each flank, and small ramps communicate from thence with the ditch along the faces. The communication with the ravelin, from the ditch of its redoubt, consists of a single pas de souris constructed near the extremity of each face of the ravelin, opposite the postern of the redoubt, besides a double pas de souris at the circular part of the counterscarp of this work; whilst the communication from the main ditch with the redoubts of the re-entering places of arms takes place by means of a pas de souris, either single or double, which is made at the re-entering angle of the gorge. From the ditch of these redoubts,

two single pas de souris, one at each end of the counterscarp, lead to the terreplein of the re-entering places of arms, and double pas de souris are made in the circular parts of the counterscarp at the gorge of the saliant places of arms, in order to ascend upon their terreplein.

When the ditch of the ravelin is not so deep as the principal ditch, a communication from one to the other is established by means of a single pas de souris.

In respect to the caponiers and half-caponiers. besides the caponier Q, which secures the communication from the tenaille to the pas de souris at the gorge of the redoubt of the ravelin, a halfcaponier R covers, on each side of the tenaille, the passage from the opening between its profile and the flank of the bastion, to the pas de souris leading to the ditch of this redoubt, opposite its flank. A half-caponier S also traverses the main ditch, perpendicularly to the face of the bastion, for the purpose of covering, on the side towards the saliant place of arms in front of the bastion, the communication with the pas de souris at the gorge of the redoubt in the re-entering place of arms; this communication is covered on the other side, by a half-caponier T, placed across the ditch of the ravelin. A half-caponier U is likewise constructed across the ditch of the redoubt of the ravelin, which, as has been previously said, serves to secure the postern, and the pas de souris situated in that part of the ditch which is opposite the flank.

In consequence of the manner in which the gorge of the ravelin and its redoubt is determined, the besieger can see in reverse, from the crest of the glacis in front of the bastions, not only the caponier Q, but also the half-caponiers R nearest to it; and as, according to the present method of constructing all these works, they merely consist of earth, the communications which they are intended to cover do not appear sufficiently secure. It has therefore been suggested that the caponier should form a permanent work consisting of a vaulted bomb proof gallery, A, seven feet six inches high internally, and ten feet wide; this gallery should be sunk at bottom about four feet six inches below the ditch, its sides, as well as the crown of the arch, being protected by a covering of earth. In this manner the caponier, besides forming a communication of itself, will secure from the besieger's reverse fire two common caponiers constructed near it, and which, being open at top, may be covered by means of blinds, when circumstances require it.

It has been said that Cormontaingne contrived a retrenchment V for the bastions, which also answers the purpose of a cavalier; in order to construct it, draw i'k' and 'l' parallel to the faces of the bastion, at the distance of eighteen toises from them; and, at the same distance from the flanks, draw k'p' and 'o', also parallel to them, which should be produced inwardly fifteen feet beyond their intersections m' and n' with the prolongations Fq' and Wq' of the lines of defence of the collateral bastions; then join p' and o', and p'o' will represent the gorge of the retrenchment. The ditch is six toises broad, and the counterscarp parallel to i’'k' and i'l.

In a line with the face ML of the ravelin, draw gr', and, after making 't' equal to seven teises, draw t'u directed towards the extremity L of this face. For the retirade, v'w's', set off four toises from l' to v', and make v'w' perpendicular to ''; then draw i'w', and produce gr until it meets it.

The method of fortifying just explained, evidently has a great superiority over Vauban's first system, but is still liable to material defects, the principal of which are the following: :

First, with the exception of the superior polygons, and of the fronts disposed either in a straight line or on a concave-curve, the body of the place is not better secured than any other part of the fortification from the ricochet fire, which the besieger can use from the beginning of the siege; and no portion of the ground, within the sphere of the works, is sufficiently re-entering to render the attacks subject to a very effectual fire from them, in flank and in reverse; whilst the sallies are but feebly protected, and the besieger can crown at one time the whole covert-way of the front of attack, without much risk from this operation. Secondly, this system is as much deficient as that of Vauban, in places of security for the artillery and troops; the consequences of which are that no batteries can be preserved entire, for the most important period of the siege; whilst the troops after having felt the destructive effect of the ricochet fire, kept up by the besieger from the commencement of his operations, become still further exposed to such a vertical fire from his nearer batteries as must render the terrepleins almost untenable, if not entirely so.

Thirdly, although the larger size of the re-entering places of arms, besides their substantial redoubts, much improves the defence of the covert-way, yet this work can be stormed; and further improvements in its disposition are still requisite, to enable the garrison to defend it with great obstinacy.

Fourthly, the besieger can breach the body of the place through the ditch of the ravelin, even before he has taken this work; and after taking it he can execute the same operation through the ditch of the redoubt. The body of the place is also liable to be breached from the terreplein of the redoubts in the re-entering places of arms, through the openings between the profiles of the tenaille and the flanks of the bastions; and it is to be observed, likewise, that the besieger has it in his power to dislodge the garrison of the re-entering places of arms and their redoubts without making any direct attack upon these works, as, after taking the ravelin and destroying its coupures, he can advance in the rear of the above places of arms and redoubts, by means of a single sap which he constructs in the parapet of the ravelin, in order to keep up from this sap a plunging and reverse fire upon the troops stationed in them.

Fifthly, the flanking defence that the ditches of the ravelin and its redoubt receive from the faces of the bastions, is not so effectual as might be wished; and, as has been previously remarked, the ditch along the escarp of the tenaille is but imperfectly defended.

As to irregular fortifications the great variety of combinations which they require evidently shows, as colonel Malortie observes, that any expectation of acquiring an effectual knowledge of it from such general explanations, accompanied by few plates, as might be given in an ordinary treatise, or in other works of the same moderate extent, would be visionary. Indeed, the best and even the only method of gaining real information on this subject, is to learn at first the general principles of fortification, together with the use of the works most commonly employed, and the proper method of disposing them in a fortress perfectly regular. The learner is then to examine attentively plans of irregular fortresses situated in various kinds of ground, particularly those of the most celebrated fortresses, and to avail himself of any verbal explanation which experienced professional men may give him, in respect to the intended purposes and the merits of the works composing the fortresses in question; he may undoubtedly also consult the publications of such authors as have treated of irregular fortifications; and, if circumstances should allow him to visit fortresses, he certainly will derive great advantage from viewing upon the spot the fortifications and the country round them.'

We refer to the few observations of this gentleman in his treatise on Permanent Fortifications, chap. x., as well worthy the learner's particular attention.

SECT. V.-M. CARNOT'S SYSTEM.

But it is due to the reputation of Carnot, before we close this part of our subject, to notice

distinctly his New Principles of Fortification His Treatise on the Defence of Fortified Places is in very general circulation; it has been translated into our language, and the unquestionable talents of the author as a mathematician and an

engineer have powerfully patronised his theory, that a fortified place may be renderea impregnable by a general use of vertical fire.

M. Carnot tells us, that he had long been convinced of the vast advantages which would result from adopting vertical fire as the basis of defence, instead of using it as an accessory mean; but that he did not make his theory known, lest the discovery should be practised against the of fensive operations of his countrymen. 'But now,' he observes, that our enemies have few places left to defend, I no longer hesitate to render my ideas public, since any improvement in the defensive art must turn, almost exclusively, to the advantage of the French frontiers.'

That is, as Sir Howard Douglas remarks, 'when France had succeeded in establishing almost universal dominion over the continent of Europe, M. Carnot promulgated his new doctrine, in obedience, as he informs us, to the commands of Buonaparte, to show the military intrusted with the defence of the bulwarks of the state, the importance of their functions, and the extent of their obligations-the glory which attends the faithful discharge of their duties, and the misfortunes which those, who either neglect or betray them, must draw upon themselves and upon their country. This appeal was particularly addressed to the troops occupying the fortresses which the French retained in foreign territory, and to the garrisons of their frontier and interior places, at the time Napoleon began to prepare his mighty means for the Russian war. To stimulate to the utmost the defensive energies of his garrisons, the work contains succinct and very partial accounts of memorable sieges, together with a code of imperial laws detailing the circumstarces, and evidences of extremity, under which, only, governors or commandants of fortresses and places should be justified in capitulating, without incurring the severe and summary penalties denounced against those who should surrender their posts without full compliance with the terms of this decree.

'Before Napoleon entered on the remote enterprise which his insatiable ambition impelled him to undertake, it became essentially necessary to adopt every possible precaution to enforce the constancy of his allies, maintain the internal tranquillity of his empire, and stimulate elsewhere a defensive system, during the absence of the grand army; and to urge to the last extremity the defence of his frontier places, in the event of any failure in his external operations. These great objects, he rightly considered, would all be best promoted by giving to public opinion, from high professional authority, such impressions of the security in which these strong-holds were left, and of the impossibility of reducing them, as might deter enterprises of defection and conpiracy, and give enthusiastic confidence in the means of resistance. To effect this, it was necessary to assert the discovery of some fallacy in

the well known balance which, since the days of Vauban, has remained decidedly, and with calcu lable certainty, in favor of attack; but as such a revolution in public opinion could not be established by any new arrangement of known or ordinary means, M. Carnot boldly and ingeniously proclaimed the discovery of a new mode of defence, by which fortresses might be rendered absolutely impregnable, and by means so simple as to be easily adapted to all places. In promulgating this new doctrine the author has filled-in some useful materials and observations calculated to excite protracted defence; but his general reasoning is quite delusive. He wrote as a political engineer; or rather he compiled the treatise which, he informs us, Napoleon sketched; and the deduction drawn from it is, perhaps, one of the most curious and interesting passages that has every emanated from the imperial press. 'From what we have just read,' says our author, results, I think, very evidently, this tranquillising truth, that the barriers of the French empire are absolutely inexpugnable by any power, or coalition of powers, whatever, if well defended.'

The chief recommendation of this writer is, that the besieged should begin to make use of vertical fire upon the commencement of the construction of the third parallel, and from that stage of the siege keep up an incessant discharge of musketry and four-ounce iron balls, at great elevation, upon the enemy's works, so as to form a rain (pluie) of shot upon the trenches. The iron balls to be discharged from a number of twelve-inch mortars, two of which are placed in the saliants of each bastion and ravelin in the front or fronts attacked: each mortar throwing 600 balls at every discharge. He introduces his theory of the effect of these balls by observing, that of any number which fall in the trenches, the number that take effect will depend upon the proportion which the unoccupied part of the trench bears to the part which is covered by the men posted and working in it. Thus, supposing a man standing upon an horizontal plane to cover a space of about a foot square, and a man in the attitude of working somewhat more, M. Carnot calculates that the projections of the bodies of the men usually working and posted in the trenches will occupy about part of their surface; from which he infers, that of every 180 balls that fall in the trench, one should, according to the doctrine of chances, hit a man; and he does not doubt that it will put him 'hors de combat.'

The distribution which M. Carnot proposes to make of his mortars and pierriers for vertical fire, on a front of fortification, is as follows:

Three mortars in the saliant angle of each bastion and demi-lune.

Three to fire d'écharpe on each of the four branches of the covered way.

The mortars or pierriers are placea behind the ramparts in small bomb-proof casemates, each large enough to contain a mortar and two or three men. The casemates, or as M. Carnot calls them, 'petites cases blindées à l'épreuve,' for the defence of the capitals, are placed perpendicularly to the capitals of the bastions or

demi-lune; and those to defend the four branches of the covered way are placed parallel to the works behind which they are erected, forming a sort of interior enclosure at the foot of the interior slope of the rampart. A large port, or embrasure, is left in the end of each casemate to admit of the discharge of the mortar.

By this disposition the terre-plein of the rampart is left free for the reception of the ordinary artillery and musketry, which however, he says, should not be used at the same time with the 'batteries-blindées,' but, according to circumstances, in alternation with them. The artillery in the saliants are mounted en barbette, protected by merlons of sand-bags, until the ricochet batteries of attack are established; after which the ordnance of the place is to be withdrawn from the ramparts, until the fire of the ricochet batteries is masked by the advanced works of the attack. Thus, as soon as the enemy's ricochet batteries gain ascendancy over the artillery of the place, M. Carnot withdraws his ordnance and troops, and brings into action his batteries blindées,' two-thirds of which are, at this stage of the siege, furnished with guns or howitzers to fire à ricochet, and the other third armed with mortars. This arrangement of ordnance in the casemates is to continue until the third parallel be finished, when the guns and howitzers in the 'batteries blindées' are to be replaced by pierriers, which, together with the mortars, are then to discharge small iron balls, pieces of iron, case shot, shells, and stones, on the enemy's ap proaches.

This writer presses the importance of ricochet fire for defence, and says, it is not sufficiently practised. He recommends its more general application both from behind the ramparts and dry ditches and thinks it even more important in defending than in attacking a place.

'The enemy's troops,' says he,' are every night exposed, without shelter, in constructing their works and covering their parties. Now a bullet which grazes five or six times will be much more likely to do execution than a direct shot, which may either strike short of the mark, and in the next bound pass far beyond the trenches, or go over without touching at all.'

He also gravely recommends a revival of the ancient weapons, particularly the cross-bow, in the defence of fortified places, and quotes many instances of brilliant defence, in ancient and modern history, to support his doctrine of the efficacy of armes blanches.' 'A man,' says he, armed with a cross-bow, may easily discharge an arrow every minute, which is 1440 in twentyfour hours. Supposing then that the besieged employ 200 cross-bow men, there would be 288,000 arrows discharged from the ramparts in that time. But it has been shown,' he adds, 'that at least one arrow in every 180 will take effect, whence, of the whole number thrown, 1600 will do execution, from which it follows that 1600 men will be put hors de combat daily. Supposing this défense rapprochée to continue only ten days, the besiegers he calculates will have lost 16,000 men, and it would be easy to double the result by augmenting the number of cross-bowmen.'

But

M. Carnot has imbibed many of M. Follards prejudices in favor of the defensive powers o. ancient arms. The latter says 'all prejudice apart, this arm (the cross-bow) is infinitely more destructive than our musket, its force being at least equal, and its effect more certain.' our author's assertion that 200 arbalétriers would put 1600 men of the besiegers hors de combat' daily, is going much further than ever the prejudiced Follard ventured to retrograde upon the path of improvement.

M. Guichard gives more correct readings of the practice and character of ancient sieges; and to all those on whom the reasoning of Carnot, supported by the fancies of Follard, have had any effect, we recommend the perusal of that work, as a sensible antidote, M.`Guichard says, page 13, I have examined in the original language, the passages upon which he (M. Follard) appuys his system, and soon convinced myself that there is no authority for what he asserts, and that the authors express themselves very clearly upon the subjects they have undertaken to explain.' We might extract many other observations bearing with equal force upon the erroneous conclusions M. Follard has drawn ; but it is quite idle to compare modern and ancient modes of warfare for any purpose of practical utility. The invention of gunpowder turned the balance in favor of attack, and the introduction of the ricochet system has confirmed this superiority. All M. Carnot's theory and ingenuity are insufficient to restore the equilibrium of this settled preponderance. His suggestions, if strictly followed, would on the contrary turn the scale more in the direction of their present inequality, from the little vigor he excites in the first stages of defence. The introduction of artillery gives a momentum, equal to that of a battering-ram, to a cannon ball which may be projected with such a degree of accuracy, as to enable us to injure defences at very considerable distances. The largest battering-ram we read of was 120 feet long, and, including a head of cast iron of one ton and a half, was about 35,000lbs. weight. Supposing it to be worked by 500 men, each exerting a force of 70lbs. the force of momentum produced by their action, when the ram moves one foot per second, is about 35,000lbs.-The momentum of a 24lb. shot, moving with a velocity of 1500 feet per second, is about 36,000lbs. The invention of gunpowder thus proved utterly destructive of all former modes of war; and the gradual improvements made in artillery, and in the science of attack, explain the causes of what M. Carnot considers so extraordinary, when he says, page 327, from what cause does it happen that the strongest places are commonly taken in sieges which rarely exceed six weeks, and generally last only twenty-two or twenty-three days?' These are the causes which have produced the short duration of modern sieges: and it is quite useless and absurd, as colonel Douglas well observes, to attempt any comparison between the obsolete and the existing practices, with any hope of improvement.

M. Carnot closes this part of his treatise by noticing, and certainly favoring (p. 349), a