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In a line with the face ML of the ravelin, Lastly, this system has the same inconveni draw gr', and, after making rt' equal to seven ences as that of Vauban, with respect to the ret: ises, draw ť u directed towards the extremity trenchments in the bastions, the requisite quanL of this face. For the retirade, u' w' s', set off tity of timber during the siege, &c. four toises from s to v', and make u' w' perpendi- The duration of the defence which the system cular to i'l; then draw i'w, and produce gợ just described can afford, consists of thirty-six until it meets it.
days in such inferior polygons as allow the beThe method of fortifying just explained, evi- sieger to carry on the attacks upon a ravelin and dently has a great superiority uver Vauban's first the two collateral bastions, but it may be exsystem, but is still liable to material defects, the tended to forty-two or forty-four days in the other principal of which are the following :
polygons. First, with the exception of the superior po- Besides the modifications which have been lygons, and of the fronts disposed either in a effected in Cormontaingne's original system, straight line or on a concave-curve, the body of several engineers of eminence, amongst whom the place is not better secured than any other are Virgin, La Chiche, Montalembert, Bousmard, part of the fortification from the ricochet fire, Mouzé, and Carnot, have some years since pubwhich the besieger can use from the beginning lished methods of their own; but notwithstandof the siege; and no portion of the ground, ing the great ingenuity, profound views and conwithin the sphere of the works, is sufficiently siderable degree of professional knowledge, re-entering to render the attacks subject to a which these engineers have displayed in their very effectual fire from them, in flank and in re- productions, yet they have not entirely solved verse; whilst the sallies are but feebly protected, the very difficult problem of contriving a system and the besieger can crown at one time the of fortification to which no well-founded objecwhole covert-way of the front of attack, without tions can be made. The reader, however, will much risk from this operation. Secondiy, this derive much benefit from making himself acsystem is as much deficient as that of Vauban, in quainted with the several systems, according to places of security for the artillery and troops; his professional or other connexions with this the consequences of which are thai no batteries art, as well as with the reasonings of their aucan be preserved entire, for the most important thors in order to support them; and particularly, period of the siege; whilst the troops after if not being yet sufficiently proficient in fortifihaving felt the destructive effect of the ricochet cation to trust to his own discrimination, he confire, kept up by the besieger from the commence- sults the judicious analysis of those systems ment of his operations, become still further ex- which men of experience have given. posed to such a vertical fire from his nearer bat- As to irregular fortifications the great variety teries as must render the terrepleins almost un- of combinations which they require evidently tenable, if not entirely so.
shows, as colonel Malortie observes, that any Thirdly, although the larger size of the re-en- expectation of acquiring an effectual knowledge tering places of arms, besides their substantial of it from such general explanations, accomparedoubts, much improves the defence of the nied by few plates, as might be given in an covert-way, yet this work can be stormed; and ordinary treatise, or in other works of the same further improvements in its disposition are still moderate extent, would be visionary. Indeed, requisite, to enable the garrison to defend it with the best and even the only method of gaining great obstinacy.
real information on this subject, is to learn at Fourthly, the besieger can breach the body first the general principles of fortification, of the place through the ditch of the raveling together with the use of the works most comeven before he has taken this work; and after monly employed, and the proper method of taking it he can execute the same operation disposing them in a fortress perfectly regular. through the ditch of the redoubt. The body of The learner is then to examine attentively plans the place is also liable to be breached from the of irregular fortresses situated in various kinds terreplein of the redoubts in the re-entering places of ground, particularly those of the most celeof arms, through the openings between the pro- brated fortresses, and to avail himself of any files of the tenaille and the flanks of the bastions; verbal explanation which experienced profesand it is to be observed, likewise, that the be- sional men may give him, in respect to the insieger has it in his power to dislodge the garrison tended purposes and the merits of the works of the re-entering places of arms and their re- composing the fortresses in question; he may doubts without making any direct attack upon undoubtedly also consult the publications of these works, as, after taking the ravelin and de- such authors as have treated of irregular fortifistroying its coupures, he can advance in the rear cations; and, if circumstances should allow him of the above places of arms and redoubts, by to visit fortresses, he certainly will derive great means of a single sap which he constructs in the advantage from viewing upon the spot the fortiparapet of the ravelin, in order to keep up from fications and the country round them.' this sap a plunging and reverse fire upon the We refer to the few observations of this gentroops stationed in them.
tleman in his treatise on Permanent FortificaFifthly, the flanking defence that the ditches tions, chap. X., as well worthy the learner's parof the ravelin and its redoubt receive from the ticular attention. faces of the bastions, is not so effectual as might be wished; and, as has been previously re
Sect. V.-M. CARNOT'S SYSTEM. marked, the ditch along the escarp of the te- But it is due to the reputation of Carnot, benaille is but imperfectly defended.
fore we close this part of our subject, to notice
distinctly his New Principles of Fortificationthe well known balance which, since the days of His Treatise on the Defence of Fortified Places Vauban, has remained decidedly, and with calcu is in very general circulation; it has been trans- lable certainty, in favor of attack; but as such a lated into our language, and the unquestionable revolution in public opinion could not be estabtalents of the author as a mathematician and an lished by any new arrangement of known or engineer have powerfully patronised his theory, ordinary means, M. Carnot boldly and ingethat a fortified place may be renderea impregna- 'niously proclaimed the discovery of a new mode ble by a general use of vertical fire.
of defence, by which fortresses might be renM. Carnot tells us, that he had long been dered absolutely impregnable, and by means so convinced of the vast advantages which would simple as to be easily adapted to all places. In result from adopting vertical fire as the basis of promulgating this new doctrine the author has defence, instead of using it as an accessory mean; filled-in some useful materials and observations but that he did not make his theory known, lest calculated to excite protracted defence; but his the discovery should be practised against the of- general reasoning is quite delusive. He wrote fensive operations of his countrymen. *But as a political engineer; or rather he compiled now,' he observes, that our enemies have few the treatise which, he informs us, Napoleon places left to defend, I no longer hesitate to sketched ; and the deduction drawn from it is, render my ideas public, since any improvement perhaps, one of the most curious and interes:in the defensive art must turn, almost exclusively, ing passages that has every emanated from the to the advantage of the French frontiers.'
From what we have just real,' That is, as Sir Iloward Douglas remarks,“when says our author,' results, I think, very evidently, France had succeeded in establishing almost this tranquillising truth, that the barriers of the universal dominion over the continent of Europe, French empire are absolutely inexpugnable by any M. Carnot promulgated his new doctrine, in power, or coalition of powers, whatever, if well obedience, as he informs us, to the commands defended.' of Buonaparte, to show the military intrusted The chief recommendation of this writer is, with the defence of the bulwarks of the state, the that the besieged should begin to make use of importance of their functions, and the extent of vertical fire upon the commencement of the contheir obligations the glory which attends the struction of the third parallel, and from that faithful discharge of their duties, and the misfor- stage of the siege keep up an incessant discharge tunes which those, who either neglect or betray of musketry and four-ounce iron balls, at great them, must draw upon themselves and upon elevation, ipon the enemy's works, so as to form their country. This appeal was particularly ad- a rain (pluie) of shot upon the trenches. The dressed to the troops occupying the fortresses iron balls to be discharged from a number of which the French retained in foreign territory, twelve-inch mortars, two of which are placed in and to the garrisons of their frontier and interior the saliants of each bastion and ravelin in the places, at the time Napoleon began to prepare his front or fronts attacked : each mortar throwing mighty means for the Russian war. To stimulate 600 balls at every discharge. He introduces his to the utmost the defensive energies of his gar- theory of the effect of these balls by observing, risoris, the work contains succinct and very par- that of any number which fall in the trenches, tial accounts of memorable sieges, together with the number that take effect will depend upon a code of imperial laws detailing the circum- the proportion which the unoccupied part of the starces, and evidences of extremity, under which, trench bears to the part which is covered by the only, governors or commandants of fortressesmen posted and working in it. Thus, supposing and places should be justified in capitulating, a man standing upon an horizontal plane to cover without incurring the severe and summary penal- a space of about a foot square, and a man in the ties denounced against those who should sur- attitude of working soinewhat more, M. Carnot render their posts without full compliance with calculates that the projections of the bodies of the terms of this decree.
the men usually working and posted in the . Before Napoleon entered on the remote enter- trenches will occupy about abo part of their surprise which his insatiable ambition impelled him face; from which he infers, that of every 180 to undertake, it became essentially necessary to balls that fall in the trench, one should, according adopt every possible precaution io enforce the to the doctrine of chances, hit a man; and he does constancy of his allies, maintain the internal no doubt that it will put him "hors de combat.' tranquillity of his empire, and stimulate else- The distribution which M. Carnot proposes to where a defensive system, during the absence of make of his mortars and pierriers for vertical fire, the grand army; and to urge to the last ex- on a front of fortification, is as follows :tremity the defence of his frontier places, in the Three mortars in the saliant angle of each event of any failure in his external operations. bastion and demi-lune. These great objects, he rightly considered, would Three to fire d'écharpe on each of the four all be best promoted by giving to public opinion, branches of the covered way. from high professional authority, such impressions The inortars or pierriers are placea behind the of the security in which these strong-holds were ramparts in small bomb-proof casemates, each left, and of the impossibility of reducing them, large enough to contain à mortar and two ur as might deter enterprises of defection and con- three men. The casemates, or as M. Carnot spiracy, and give enthusiastic confidence in the calls them, “petites cases blindées à l'épreuve,' means of resistance. To effect this, it was ne- for the defence of the capitals, are placed percessary to assert the discovery of some fallacy in pendicularly to the capitals of the bastions or
demi-lune; and those to defend the four bran- M. Carnot has imbibed many of M. Follard's ches of the covered way are placed parallel to prejudices in favor of the defensive powers of the works behind which they are erected, form- ancient arms. The latter says “all prejudice ing a sort of interior enclosure at the foot of the apart, this arm (the cross-bow) is infinitely more interior slope of the rampart. A large port, or destructive than our musket, its force being at embrasure, is left in the end of each casemate to least equal, and its effect more certain. But admit of the discharge of the mortar.
our author's assertion that 200 arbalétriers would By this disposition the terre-plein of the ram- put 1600 men of the besiegers “hors de combat' part is left free for the reception of the ordinary daily, is going much further than ever the preartillery and musketry, which however, he says, judiced Follard ventured to retrograde upon the should not be used at the same time with the path of improvement. " batteries-blindées,' but, according to circum- M. Guichard gives more correct readings of stances, in alternation with them. The artillery the practice and character of ancient sieges; in the saliants are mounted en barbette, protected and to all those on whom the reasoning of Carby merlons of sand-bags, until the ricochet bat- not, supported by the fancies of Follard, have teries of attack are established; after which the had any effect, we recommend the perusal of ordnance of the place is to be withdrawn from that work, as a sensible antidote, M. Guichard the ramparts, until the fire of the ricochet batte- says, page 13, I have examined in the original ries is masked by the advanced works of the language, the passages upon which he (M. Folattack. Thus, as soon as the enemy's ricochet lard) appuys his system, and soon convinced batteries gain ascendancy over the artillery of myself that there is no authority for what he asthe place, M. Carnot withdraws his ordnance serts, and that the authors express themselves and troops, and brings into action his batteries very clearly upon the subjects they have underblindées,' two-thirds of which are, at this stage taken to explain.' We might extract many other of the siege, furnished with guns or howitzers to observations bearing with equal force upon the firc à ricochet, and the other third armed with erroneous conclusions M. Follard has drawn; mortars. This arrangement of ordnance in the hut it is quite idle to compare modern and casemates is to continue until the third parallel ancient modes of warfare for any purpose of be finished, when the guns and howitzers in the practical utility. The invention of gunpowder " batteries blindées' are to be replaced by pier- turned the balance in favor of attack, and the riers, which, together with the mortars, are then introduction of the ricochet system has confirmed to discharge sinall iron balls, pieces of iron, this superiority. All M. Carnot's theory and case shot, shells, and stones, on the enemy's ap- ingenuity are insufficient to restore the equiliproaches.
brium of this settled preponderance. His sugThis writer presses the importance of ricochet gestions, if strictly followed, would on the fire for defence, and says, it is not sufficiently contrary turn the scale more in the direction of practised. He recommends its more general ap- their present inequality, from the little vigor he plication both from behind the ramparts and dry excites in the first stages of defence. The introditches : and thinks it even more important in duction of artillery gives a momentum, equal to defending than in attacking a place.
that of a battering-ram, to a cannon ball which • The enemy's troops,' says he, “are every night may be projected with such a degree of accuracy, exposed, without shelter, in constructing their as to enable us to injure defences at very conworks and covering their parties. Now a bullet_siderable distances. The largest battering-ram which grazes five or six times will be much more we read of was 120 feet long, and, including a likely to do execution than a direct shot, which head of cast iron of one ton and a half, was may either strike short of the mark, and in the about 35,000lbs. weight. Supposing it to be next bound pass far beyond the trenches, or go worked by 500 men, each exerting a force of over without touching at all.'
70lbs. the force of momentum produced by their He also gravely recommends a revival of the action, when the ram moves one foot per second, ancient weapons, particularly the cross-bow, in is about 35,000lbs.—The momentum of a 241b. the defence of fortified places, and quotes many shot, moving with a velocity of 1500 feet per instances of brilliant defence, in ancient and second, is about 36,000lbs. The invention of modern history, to support his doctrine of the gunpowder thus proved utterly destructive of efficacy of armes blanches. A man,' says he, all former modes of war; and the gradual im‘armed with a cross-bow, may easily discharge an provements made in artillery, and in the science arrow every minute, which is 1440 in twenty- of attack, explain the causes of what M. Carnot four hours. Supposing then that the besieged considers so extraordinary, when he says, page employ 200 cross-bow men, there would be 327, ‘from what cause does it happen that the 288,000 arrows discharged from the ramparts in strongest places are commonly taken in sieges that time. But it has been shown,' he adds, which rarely exceed six weeks, and generally 'that at least one arrow in every 180 will take last only twenty-two or twenty-three days?' effeot, whence, of the whole number thrown, 1600 These are the causes which have produced the will do execution, from which it follows that short duration of modern sieges: and it is quite 1600 men will be put hors de combat daily. useless and absurd, as colonel Douglas well Supposing this défense rapprochée to continue observes, to attempt any comparison between only ten days, the besiegers he calculates will the obsolete and the existing practices, with any have lost 16,000 men, and it would be easy to hope of improvement. double the result by augmenting the number of M. Carnot closes this part of his treatise by cross-bowmen.'
noticing, and certainly favoring (p. 349), a
singular idea of a M. Flachon de la Jomarière, The ditch of the bastion is thirty-six feet who proposes to pour upon the besiegers, when wide. Counterguards are placed before the basthey are about to crown the covered-way, an tions. The demi-lunes are works of the same enormous quantity of water from powerful en- profile as the counterguards. Sometimes M. gines, which, he says, will make the soil so Carnot calls his counterguards and demi-lunes liquid that it cannot be worked.
glacis coupés, and under this name recommends His New System of Improving Fortifications them for improving the defences of existing is, of course, grounded on these principles. "The places. The cavaliers are placed in front of the spirit,' says A. Carnot, of the new system of tenailles, and communicate with them by caponfortification, consists in procuring, by the nières. ticular combination of the parts which compose The counterguards and demi-lunes have ditches it, numerous debouches on all the avenues of the thirty-six feet wide at bottom, the counter slopes place, so that the besiegers may not be able to forming a reverse glacis of forty-three yards establish themselves near it without being ex- which M. Carnot calls glacis en contrepente. posed to be suddenly attacked, at all times, by In old fortresses M. Carnot proposes to conall the garrison. From this the enemy will not vert a portion of each bastion into a counterbe able to present bimself any where, without guard, hy making a ditch, about thirty-six feet keeping troops constantly drawn out, ready to wide across the bastion, from the middle of each repulse any sortie the besieged may unexpectedly flank, in the directions of lines of defence; the two make, and which they may renew whenever they branches of the ditch meeting, consequently, on please. The besiegers will therefore be obliged the capital. The part thus enclosed is formed to accumulate troops on all parts of the immense into a bastion, by making parapets upon the incircumference which they must occupy, to em
terior lines of the ditch, which thus become the brace the defences of the place; and as in the faces of a bastion so sinall that its flanks are but défense raprochée all this development of force sixty feet long-sufficient only to receive three is within the influence of vertical fire, showers ,guns. The new ditch is consequently very little of projectiles will carry off some men every defended by Hank-fire; but this, consistently moment, and at length entirely crush the be- with the principles already noticed, M. Carnot siegers.'
has here also sacrificed to the superiority of verThis torrent of vertical fire' is thrown from tical fire. casemated mortar-batteries, the positions of For the purpose, chiefly, of being able to inakę which are determined from an acknowledged sorties with facility, M. Carnot proposes to condefect in Vauban's systems, viz. the deficiency vert the glacis into a glacis en contrepente, and, of fire on the prolongations of the capitals of the with the earth furnished by the excavation, to bastions, but which fault M. Cormontaingne has form the upper part of the old glacis into a remedied by constructing redoubts in the re- counterguard or glacis coupé, raised nearly as entering places of arms.
high as the body of the place. The interior M. Carnot's ideas of the irresistible effect, slope of the new work occupies the greater part and exclusive advantage, of this profusion of of the old covered-way: The traverses are revertical fire in defence, are such, he asserts, moved; and, instead of palisades, a brick wall P. 445, that it will change entirely the character furnished with loop-holes is constructed very of the operations of a siege. “According to the near the counterscarp.
The exterior slope of existing practice,' he says, “the besiegers are the glacis coupé is so abrupt that no part of it covered, and the besieged exposed. In the new can be seen from the body of the place; and the system, on the contrary, the besieged are covered, greater part of the advanced ditch formed by but the besiegers exposed to a profusion of feux this alteration cannot be seen at all. verticaux, which will reach them behind their Colonel Sir Howard Douglas has published parapets and lodgments, enabling the besieged to. some spirited and scientific Observations on the defend their out-works, without occupying them, Motives, Errors, and Tendency of M. Carnot's merely by pouring upon them torrents of vertical Principles. We have already quoted this writer, fire when the assailants move forward to the and it is but fair to add, that he seems to make attack.'
a formidable attack upon the principles and M. Carnnt then arranges his new system; the constructions of that able engineer. We abstract casemated mortar-batteries are placed in interior a sufficient portion of his remarks and experienclosures in the gorges of the bastions, so as to ments to place the whole subject fairly before the fire in the direction of their capitals. There reader. are nine casemates in each battery: of these, It is quite clear,' observes this writer, 'that M. seven contain mortars or pierriers, two in each; Carnot has formed his theory upon the parabolic the other two (the extreme casemates) are each hypothesis, which, I must inform such readers armed with three guns, for the defence of the as are not acquainted with these matters, is the ditch of the retranchement général. The escarpe theory of a projectile's flight in a non-resisting of the retranchement général is a detached wall medium. This theory, considerably erroneous placed in front of the rampart, leaving a chemin in all cases, is particularly and greatly so with des rondes eighteen feet wide. The exterior small projectiles; and its deductions, as applied slopes of the ramparts are all forty-five degrees. to the velocity of descent of small balls used in The bastions are also covered by a detached wall very elevated short ranges, are quite fallacious. erected near the base of the exterior slope of the The velocity of the hall in a horizontal direction rampart, leaving a chemin des rondes six feet (which by this theory would be constant, and to wide.
the projectile velocity as radius to the cosine
of the angle of elevation) being inconsiderable, inch, two lives, five points, which, reduced to it is evident that the effect of vertical fire must English measure, is 1-28038 inches. depend upon the velocity of descent in the di- Its content is 1.09909 inches. rection of the curve. Estimating this according to The weight is 4.72247 ounces, if made of cast the parabolic theory (as the secant of the angle of iron, and 4.8624 ounces if of wrought iron. elevation), the motion would be slowest at the ver- The terminal velocity of the cast-iron tex of the curve, and the velocities of the projec- ball is about
201 feet tile be equal at equal distances from that point. The terminal velocity of the wroughtAccording to this supposit we should sign iron ball is about
204 to the descent of small balls, discharged at an The potential altitude of the cast-iron elevation of seventy-five degrees, or eighty de
ball is about
631 grees, such accelerated velocities, as would, if Ditto ditto wrought ditto ditto 650 true, be quite sufficient to do good service in the • M. Carnot recommends that the balls should way M. Carnot suggests; but the fact is, that be made of hammered iron; but adds, that, as there can be no acceleration beyond a limit the charge of powder for a mortar is sinall, balls which, with small balls, is very much less than of cast-iron may resist the explosion without is generally imagined. From the vertex of the breaking, and will answer as well
. Now this curve, where all the vertical motion is lost, the observation shows that the author had not conball begins to descend hy an urging force which sidered the effect of the air's resistance, nor is nearly constant, viz. 'its own weight. This doubted a sufficiency of force in his vertical force would produce equal increments of ve- fire: for the weight of a ball of hammered iron locity, in equal times in vacuo, but in air, the is greater than that of a ball of cast-iron of equal descent of the ball being resisted more and more diameter, and the superior weight or urging as the velocity accelerates, the urging force will, force of the former would generate greater terat a certain velocity, be opposed by an equal minal velocity than a lighter ball of the same resistance of air, after which there can be no size could acquire; the momenta of the two balls further acceleration of motion, and the ball will in question would be as nineteen to eighteen. continue to descend with a velocity nearly ter- . Four-ounce balls, discharged at elevations minal.
even considerably above forty-five degrees, to When I began to consider this interesting the distance of 120 yards, would not inflict a problem, as applied to vertical fire, I was soon mortal wound, excepting upon an uncovered satisfied that M. Carnot had entirely overlooked head. They would not have force sufficient to terminal velocity; and I shall show, from his break any principal bone; there would be no own words, that this is the case. It is not ne- penetration, but merely a contusion. This cercessary to exhibit bere the investigations by which tainly would not oblige the besiegers to cover I have established the impotency of M. Čarnot's themselves with blindages, as M. Carnot imavertical fire; I shall only state the results, not gines ; for a strong cap or hat, and a cover of to embarrass the conclusions with abstruse mat- thick leather for the back and shoulders, would ter. The solutions are computed from the theo- be sufficient protection from the effects of his rems given in Dr. Hutton's tracts, and, although vertical fire with small balls. As the quantity the results may differ a little from the truth, yet of balls required to feed mortars discharging 600 it is quite clear, that in the descent of the balls balls at a time would be very considerable, M. there can be no acceleration of motion beyond Carnot observes that cubes of iron of eight or a certain limit; that with small balls this ve- ten lines side, cut from square bars of this dilocity is very much less than persons who have mension, may be substituted. These, he says, not investigated this curious problem would may be fired from mortars, howitzers, or stoneimagine; and that M. Carnot has evidently mortars, and will produce the same effect as balls overlooked this circumstance.
(page 491, Carnot). "The velocity which a musket ball has acquired Let us consider this: when the resistance becomes equal to the weight, Ten lines French are equal to ·89523 in. English. or urging force of descent, is only about 180 The content of the cube is .71746 feet in a second. The potential altitude, or the Its weight is
3.0822 ounces. height from which the ball must descend in vacuo,
Now take a ball of the same weight: to acquire a velocity equal nearly to the termi- Its diameter is
1.111 inches. nal velocity, is 523 feet. Hence, in the first Its terminal velocity is 185 feet per sec. place, it would be a waste of means to use the Its potential altitude is 534 feet full charge; for a inusket ball fired upwards, •We have no experiments from which we can with the ordinary quantity of powder, would be ascertain the terminal velocity of square shot; projected to a greater height than 523 feet; and but, from comparative experiments with round it is evident that all above this is unnecessary. and flat surfaces, we know that the resistance of The indentation which a musket ball, moving the air to the flat end of a cylinder is more with a velocity of 180 feet per second, makes than double the resistance to a ball of the same on a piece of elm timber, is about to of an inch : diameter. Thus, although the urging force of a this might, perhaps, be sufficient to knock a man ball and cube of the same weight be the same, down, if by great chance it were to fall upon his yet the surfaces upon which the resistance acts head; but in no other case would it put him (and very irregularly in regard to the cube) are hors de combat.'
very different: * Now, as to the four-ounce balls. The The surface of the ball is .
3.87045 diameter of a French four-ounce ball is one
the cube is.