« ZurückWeiter »
From this, together with what has been said nor the couronnement of the glacis, are within respecting the descent of balls, we know, and the reach of stones forced to the utmost, from that is enough for our present purpose, that the pierriers in the casemated battery; and the horiterminal velocity of the cube must be much less zontal area of all those parts of the attack which than 185 feet per second; and consequently its come within its influence is so small, compared effect or momentum inferior to that of a 3.08 with the vast magnitude of the oval surface upon ounce ball. The motion of a cubical shot will, which the stones fall, that, it may be relied upon, besides, be quite irregular, descending sometimes not one stone in 1000 would take effect upon the with an angle, then a face, then an edge foremost, besiegers. tumbling over and over in oblique, irregular di- A substitution of large balls and grenades, rections, without any certainty, excepting that adds this writer, fired from mortars, would be less the velocity and effect will be much less than uncertain and more formidable; but even with those of a round shot of equal weight.
these the dispersion is very great. 100 iron balls, of Our author smiles at the preference of the one pound each, were discharged from a ten-inch French writer for cross bows and ancient wea- iron mortar, at forty-five degrees elevation, with pons of attack and defence; and compares the a charge of 1 lb. 4 oz. of powder. The spread far shorter time in which Calais, Tournai, was fifty yards; the nearest effect 150, and the Thouars, Naples, &c., have fallen before fire- furthest 210 yards : the longitudinal dispersion arms. He contends that sieges became uniformly was therefore sixty yards, and consequently the shorter as gunnery was improved. Upon the area of the surface affected by the descent of the main topic of this writer, he adds, “I give the balls, supposing it to be an ellipse whose axes results of some very careful experiments, made are sixty and fifty yards, was 20,476 square feet. purposely to ascertain the precise effects of those The chances of hitting would therefore be very natures of vertical fire, which M. Carnot pro- remote, whilst the expenditure of iron would be poses to adopt as the principal means of de- immense. At the rate of discharge which M.
Carnot mentions, page 231, it would require a
provision of nearly 1,500,000 lbs. of iron for the • Experiments with different charges of stones from a ten-inch iron mortar. Elevation 45o.
"In regard to the display of vigor and resolu1. Charge 10 oz. of powder, and fifty fint tion in personal conflict, which M. Carnot seems stones, each about 14 oz. The average range to think comparatively deficient in modern dewas 107 yards; but most of the stones were fences, it is clear,' says the above writer,' that the blown to pieces.
invention of gunpowder has narrowed the oppor2. Charge 12 oz. of powder, and forty stones tunities of displaying those qualities in the operaof hard granite of about 1 lb. each. The nearest tions of a siege, properly conducted, more than in stones fell at forty, and the furthest at 120 yards; any other military enterprise. There is no opporhe transverse spread was thirty yards.
tunity for personal conflict, excepting in sorties, 3. Charge 16 oz. of powder, and forty-six which, we have already shown, prove too fretones, as before. The nearest stones fell at quently but a waste of life and valor, and in the fty, and the furthest at 130 yards from the defence of breaches, where also there is that to
ortar: the spread was forty-five yards. One encounter which the ancients were not exposed is one went off to the right in an angle of about to. M. Carnot's object in quoting so many
rty-five degrees, and fell at the distance of 100 sieges, is, to show that the defence of places by
ads in that direction, very near a spectator (armes blanches' has constantly been more bril20 aced, as he thought, in perfect safety.
liant, more efficacious, of longer duration than
by armes à feu. What, he says (p. 239), has the zero speriments with a brass pierrier. Diameter
eter invention of powder, or the new process of De sirteen inches. Elevation 45o.
attack, to do with the vigor and resolution that Charge 2} lbs. of powder (which filled the were used by the ancients? These, he observes, mber), and 100 granite stones of 1 lb. each, may alter the means but not the principles of 250 d up to the mouth of the pierrier in a basket resistance. 1174 h a bottom of wood. The nearest effect was Now here we differ from M. Carnot; and to
8nty-eight yards; the furthest 300 : the spread close properly with this assertion, we have, rather e o seventy yards. Many of the stones broke. fully, compared the ancient with the modern 1:11? Charge 13 lb, of powder, and seventy-five means of attack, for the purpose of showing that 185ite stones of 13 lb. each. The nearest effect the general principles as well as means of de5341 twelve yards, and the furthest 180. The fence are altered, and that both are inferior to rom * ad was fifty yards.
those of attack when directed by scientific of both cases it could not well be ascertained intelligence, and furnished with sufficient means. mense the greatest effect was, on account of the What can personal vigor and resolution do at the dispersion of the stones, many of which against the establishment of the ricochet battecalore even with the reduced charge.
ries, and all the process of attack, until it come ahal plying these experiments to the new de- near enough to be checked by sorties? The dese urek s of M. Carnot, Sir Howard found that the fence by armes blanches' can only be applied Feigt st effect would take place in the gorge of to the defence of a breach; but a breach may
the plastion; and that the furthest effect, P, always be made, whatever be the vigor, resoluand to I., would not reach the crest of the glacis, tion, or strength of the garrison. The only
with the full charge of powder. It appears, means to oppose and retard the opening of a
bre, says he, that neither the third parallel, breach are by a powerful fire of artillery in the .. Vol. IX
first instance, then by counter-mines, and oc- and any other destructive missile that can be casionally by sorties. These may, at a great procured; and that a deep trench, previously sacrifice, retard the operation, but cannot alto- dug and filled with tarred faggots, and other gether defeat it. Do not these alter the princi- , combustible materials, should be set on fire when ples as well as the means of defence? The the storming party is about to mount the breach. sieges of the ancients gave occasion for a great He also recommends (p. 297) cuts to be made many personal conflicts from the beginning into the parapet, on the flanks of the breach, of the enterprise; and so did modern sieges, from which the besieged can either fire, or drop until parallels or places of arms were ap- shells upon the assailants ;-an expedient which, plied to protect the approaches and repel sor- after the breach is carried, will prevent the enemy ties : but there is now no such field for personal from extending himself, by sapping in the parapet, prowess, and a place may certainly be breached, towards the shoulders and gorge of the bastion and exposed to the consequences of an assault, to the attack of the retrenchments. But, whatwithout giving the besieged any favorable op- ever obstacles and expedients be applied to close portunity of displaying personal exertion with the breach, they will inevitably be destroyed, i armes blanches.' The operations of a siege, broken, or deranged by the heavy fire from the to this period, are chiefly what the French call breaching batteries established on the crest of 'par industrie,' which, instead of being secon-. the glacis, which is always the iminediate predary, as M. Carnot says, to the objects of per- lude to an assault. Consequently little reliance sonal valor, are the means which introduce the should be placed on any other means than the display of it; and we cannot see that his reason- personal valor and determination of the troops ing can attach to any thing but the defence of a actually placed behind these obstacles, who breach. With this also gunpowder has, or at should there use the most determined, devoted least ought to have, a great deal to do; for the exertions to prevent the enemy from gaining a guns that made the breach, can render it practi- footing on the breach. According to M. Carcable; they can prevent the besieged from closing not's method of opposing an assault, a footing it by exterior obstacles, and the interior defences might be gained, and a lodgment partly formed, may be molested by shells, stones, &c. M. , before the corps d'élite could be drawn out from Carnot applies personal valor and determination their cover, and march forth to balayer' the less, in the first instance, to the defence of a rampart ; and when once a footing is obtained, breach than we should do. He proposes (p. or a lodgment made, it is not easily recovered, 333, 4to. edition) to have fifteen or twenty 'pier- if proper measures have been taken to support riers blindés' ranged round the breach as a focus, the assault; and the attempt is always very and to keep near them, also under cover, a corps bloody and seldom successful. d'élite ready to march forth. When the besie M. Carnot inserts a loug quotation from the ger's troops put themselves in motion, to advance Sieur Antoine de Ville's Ingénieur parfait, pubto the assault, M. Carnot recommends that the lished in 1629, which, he says, only requires troops should be withdrawn from the rampart, some modifications which follow from the imin order to allow the stone-mortars to act. It is provements that have been made in fire-arms evident, he observes, that the enemy either will since the period in which this work was written. not arrive, or if he does, that it will be in dis. This passage commences in the original (book order, after immense loss from the fire of the iii. part ii. p. 372) with an enunciation (which stone-mortars; 'upon which the fire should M. Carnot suppresses, as he does several other suddenly cease, the corps d'élite march forth, parts of the passage), which shows how comcharge the enemy, and will very soon sweep pletely the author's directions must be considered, them from the field of battle, whilst a good sortie as indeed they are, obsolete. In proportion,' will take them in flank and rear, destroy their says M. de Ville, .as the enemy make a breach, epaulement,' &c. This is indeed a sweeping the besieged should endeavour during the followclause in M. Carnot's theory, and there needs no ing night to undo his work, restore, and throw it comment to show that it is the most fallacious up again. Whoever reads this passage in the part of his doctrine. The way to oppose an original will perceive that very little of it can assault is undoubtedly to render the breach as apply at all to the defence of a breach made by inaccessible as possible, by every obstacle that a battery established on the crest of the glacis, can be applied, and to hurl upon the storming in a face which has been ricoched from the comparty quantities of stones, live-shells, grenades, mencement of the siege, and whose acting flanš combustibles, &c.; and some of the expedients is directly counter-battered, and also enfiladed proposed by M. Carnot for these purposes, and from the third parallel. It were madness indeed practised by the French in the Peninsula, are to attempt to defend a breach made in this reguamong the best parts of his elaborate treatise. lar way, unless the besieged have a retrenchment. He recommends, p. 310, that the breach should M. Carnot may adduce, and my readers may. be strewed with crow's feet, harrows, chevaux- recur to, the sieges made in the Peninsula, in de-frise, &c.; and that when the assault is about opposition to this assertion; bui we bave the to be made, or expected to take place, the be- public authority of a rery distinguished British sieged should form a barrier on the summit of engineer (lieutenant-colonel Jones) to remark, the breach, of strong six-pointed crow's feet, that those sieges having been undertaken and made of wood armed with iron points, firmly executed under circumstances and deficiencies fastened to each other : that when the storming which did not admit of regular attacks accordparty advances to the assault, they should be as- ing to established rule, cannot be received as sailed with a prodigious quantity of combustibles cases which afford any reason for departing from
cong-established practice; and that the defence and, the length of the parapet remaining the of the breaches at Badajoz, which has thrown same, you ought to enclose within it the greatest some popular lustre on M. Carnot's work, could possible surface. not have succeeded against an attack conducted, 10. Before you begin a work, you ought to throughout, according to regular process. M. ascertain whether you have sufficient means for Carnot may perhaps dispute illustrations from completing it in time. British talent and experience, or we should have We can only find room for a sketch of the presented him with other references to facts con- principal or out-line of field-works. tained in colonel Jones's excellent work, in sup- of redans or flêches, As redans or flèches, port of other parts of our reasoning.'
plate VI. fig. 3, can be quickly and easily conPART II.
structed, they are frequently used in the field,
where few means are at hand; besides, in many OF FIELD FORTIFICATION.
circumstances, the intended object of a work Field, or temporary fortification, having the does not require that it should be able to afford same general objects as more permanent works, an obstinate defence. Weak indeed is that only differs from them in the means that may be which a redan can make, particularly when accessible for attacking or defending them. isolated; for then, independent of being easily
Field works are thrown up, merely for a short carried in front, owing to the undefended sector time: often in haste, without either choice or fag, its gorge b c is also greatly exposed, and preparation of the materials employed; with you ought not to rely on the defence of a redan, very few means at hand, and sometimes in unless it is supported in its rear; such as, for presence, as it were, of the enemy; besides, instance, redans thrown up in front of an army there are many cases in which they are not in- you intend to intrench, and on the banks of a tended to resist an attack supported by cannon, river to cover a bridge, or defend a ford. and, when they are, the nature of the guns which Sometimes redans are placed in front of a will prohably be brought against them may be main work, either to cover its communications different, according to the importance of the with the country, or to defend some parts of the works. Lastly, field-works are usually attacked ground which cannot be seen from it, and would by troops formed into columns; which, advanc- be of advantage to the enemy in directing their ing rapidly in the direction of their capitals, attacks: or in short to procure a cross fire on threaten many points at once; therefore, the the capitals of the main work, and keep the dispositions for their defence, ought to be differ- enemy at a distance from it. Redans so disent from those of permanent works, &c. The posed are called lunettes. maxims or general rules that are to be observed. No fixed rules can be given with regard to the in them are;
length and direction of the faces of a redan, 1. In general, a saliant angle should not be since both vary according to the ground, the inless than sixty degrees, especially when it is un- tended object of the work, and the strength of defended by any fank fire.
the detachment that it is to cover, &c. 2. The saliants being the most exposed points, of redoubts.-Redoubts, as well as redaus, particularly when they are not flanked, their are frequently used in the field; where, as isodefence ought to be carefully attended to; when lated works, they are employed, when the post the ground, and intended object of the work you or detachment to be intrenched being abandoned construct, will allow you to direct the saliants to its own strength, and without any protection towards some natural obstacles which prevent in its rear that may prevent its being turned, it the enemy approaching them on the prolonga- becomes necessary to enclose it entirely, so as to tion of the capitals, you ought to avail yourself of secure it from the attacks which the enemy may that advantage ; but, if you cannot direct the sali- make upon it on all sides. Redoubts are exants thus, they must be protected, if possible, by tremely proper for covering an advanced post, a some artificial obstacles.
grand guard, or a communication ; for defend3. In tracing field-works, let there be as many ing a defile, a height; for protecting a retreat, flank defences as possible.
the passage of a river, ford, or bridge; for sup4. When one part of a fortification is to flank porting the wings of an army, a line of frontiers, another, it must be so disposed as to make with &c.; independent of being easily constructed, it an angle not less than ninety degrees, and ex- they have also the advantage of affording a very ceeding as little as possible ninety degrees; in good defence when supported from without, and order that the ditch and counterscarp of the even of being sometimes effectually used instead part flanked, may he defended by a direct fire of fortins or field-forts, which in general require from that which flanks it.
more time and materials for their construction, 5. The length of the lines of defence ought and a more numerous garrison for their defence. not to exceed eighty toises at most.
The requisite length of the sides of a redoubt 6. Avoid the second flank defence, unless you depends, not only on the extent which the paraare obliged to have recourse to it.
pet must have, in order that the garrison may 7. Be careful not to suffer any cover in the man it properly, but on the necessary interior vicinity of a work, under which the assailants space for containing the men. It should also be may approach unperceived.
considered, whether the troops are to reside in 8. Dead angles are to be avoided as much as the work, or to remain there for a short time; as possible.
it happens, for instance, when a work is suffi9. A fortification must always be proportioned ciently near a main body of troops to comto the number of men who are to defend it; municate easily with them, and receive reinforcements, should an attack be expected; in this since it is very difficult, not to say impossible, case, it will suffice to regulate the size of the to give a general rule of computing the necesredoubt in such a manner that the number of sary length of the interior sides of redoubts acmen intended for its defence can man the para- cording to the strength of the detachments, and pet properly, without being crowded and ob- that trying is the only way.' This author's work, structed in their motions; but if the garrison is however, in which he has collected and generally to reside in the work, its interior surface must be exposed with perspicuity, most of the modern larger.
principles on which field-fortification is groundVarious methods have been proposed for cal- ed, deserves no small degree of praise. culating the necessary length of the interior M. Malortie de Martimont proposes the folsides of a redoubt, according to the strength of lowing rule, supposing the redoubts to be square, its garrison; but most have the double defect of and that the garrison is to reside within them :not being applicable to small detachments, as 1. Multiply by ten the number of men of the redoubts would then be considerably too which the detachment is composed, and the little, and to increase beyond measure the in- product will give, in square feet, the necessary terior surfaces of those works, when their garri- extent of the surface contained between the foot son exceeds a certain number of men.
of the slopes of the banquettes. The method proposed by Noizé de St. Paul, a 2. Extract the square root of that product to French engineer, is better in general than any one decimal, and it will give in feet and tenths we have seen. We shall observe, however, that of a foot, the lengths of one of the sides which it is rather complicated, as it varies according to enclose the above-mentioned surface. the strength of the detachments ; it contains, 3. Add to this length twice the number of besides, several inaccuracies; we point out the feet which the base of the interior slope of the two following:
parapet, the breadth of the banquette, and the This author says, No. 32, page 39, of his base of its slope, are to have, and the sum will work on field-fortification, if the detachment be the length, in feet and tenths of a foot, of one which you intend to place in a redoubt, is com- of the interior sides of the redoubt. posed of more than ninety men, and does not Let us suppose, for instance, that you have to exceed 120, tako dhe-fourth of the number of construct a square redoubt abc d, plate VI. fig. 4, men for a reserve, which you may make equal to for ninety men : multiply ninety by ten, and one-third of that number, if the detachment the product 900 will show that the surface ikinn, consists of 130 men or thereabout: then divide which is contained between the foot of the the remainder by eight, and the quotient will slopes of the banquettes, ought to be 900 square give the length in toises, &c., of each interior feet : extract the square root, thirty, of that proside.'-According to this rule, a detachment of duct for the length of feet in the side i k, which 100 men requires that the length of the interior is represented by a b in the profile fig. 5. Now, sides should be nearly nine toises and three supposing the base of the slope c of the banfeet; whereas it is proved by experience, that quette to be six feet, the breadth of the bancight toises and three feet, or thereabout, are quette d three feet, and the base of the interior enough; thus Noizé de St. Paul's rule increases, slope e of the parapet one foot; multiply the without necessity, the size of the redoubt, which sum of those dimensions by two, and add the requires thereby more tim?, and a greater quan- product twenty to the square root thirty which tity of materials for its construction :-besides, you have found before ; then will the sum fifty the author is inconsistent with himself; for he be the length in feet of the interior side e e fig. 5, says, p. 44, note k, in the same work, that a and cf fig. 4. It is evident, that in all redoubts detachment of 100 men requires a redoubt, constructed by this simple method, every man of whose interior sides should have from eight to the detachment has for himself ten square feet nine toises at most. But let us proceed further, of the clear surface which is contained between and suppose that the detachment consists of 120 the foot of the slopes of the banquettes; and men; according to the same rule, the interior ten feet, in addition to the space afforded by the sides of the redoubt should be eleven toises one banquettes and their slopes, as this writer confoot and six inches : but Noizé de St. Paul re- tends, will suffice in all redoubts, let their size commends the same length for those of a redoubt and figure be what they may. constructed for 180 men; since he says, p. 39, Square rodoubts are more simple and easy to
if the number of men exceeds 150, as they will construct than any other; but the configuration be able to man in two ranks the parapet of a of the ground, and the number and situation of redoubt capable of containing them, the length the points which a redoubt may have to defend, of the interior sides will be found by dividing &c., frequently require that its figure should not the detachment by sixteen. Now, why should a be square; in this case, plant staves at all the redoubt, calculated for 120 men, be exactly of points, where, in your opinion, the vertex of the tbe same size as a redoubt constructed for 180 ? angles, formed by the interior sides of the work, And is it not evident, that Noizé de St. Paul's can be placed to the greatest advantage; and method, which may give satisfactory results in after taking, with the plain table, or by any some other instances is very defective in these other means which you have at hand, the plan of two? Indeed it appears that he was aware of the figure delineated by lines which you suppose its insufficiency with regard to certain detach- to join those staves, consider it as representing the ments; for he says, No. 32, p. 40, that he interior contour of the parapet: measure the proposes it as a scale of comparison, which angles formed by those lines, in order to ascer should be used merely as a guide in practice, tain whether they are sufficiently open, Max, 1, and if some are not, rectify them : inside of the in such cases, to construct a small fortress, esplan draw a parallel to its outline, and at a pecially if you have guns to use. Star forts are distance from it, equal to the number of feet seldom constructed either in the triangular or which you intend to allow to the base of the square form, a redoubt being almost always preinterior slope of the parapet, the breadth ferable to either. In a triangle there can be no of the banquette, and to the base of its brisures, in a square their angles are 150°. siope: and, as the figure described by this A pentagon is somewhat superior to both, the parallel represents that of the space which is defence of its saliant angles being better, and the contained between the foot of the slopes of the angles of the brisure 132o. The hexagon is still banquettes, compute its area in square feet; if better than the pentagon, though its saliants are it appears from your calculations, that the re- by no means well defended. The heptagon has doubt will be considerably too large, according saliant angles of 128°, and those of the brisures to its garrison and artillery, this defect may be 112. This form might therefore be used with remedied by shortening the interior sides, or considerable advantage, were the construction diminishing their number when it exceeds four, not difficult; the most convenient, however, as or by giving a smaller opening to the angles: well as the most advantageous polygon for works but, if the work is small beyond measure, the of this kind, is the octagon. The construction is contrary should be done.
made either upon the interior polygon, by placShould a redoubt be circular, compute the ing equilateral triangles on its sides, or on the radius of the circle, bounded by the foot of the exterior side, by means of the perpendiculars slope of the banquette, so that the enclosed sur- from the saliant and re-entering angles. face may allow ten square feet to each man, and Bastion forts have often been proposed, but 324 square feet to each piece of cannon: add are inferior to star forts; the triangular half to this radius twice the base of the interior slope bastion particularly. They are difficult to conof the parapet, twice the breadth of the ban- struct; the saliants are too acute and ill-defended; quette, and twice the base of its slope; then the faces of the demi-lunes are without cover, drive a picket at the centre of the redoubt, and and the interior surface is too small. The square fasten to it one end of a cord equal to the radius half-bastion is little better than the triangular, thus increased; and with the other end, to which but it encloses a larger space. When the bastions a pointed picket is fastened, describe a circum- are full, the work may sometimes be very advanference upon the ground.
tageous, and the construction is the same as in To ascertain how many men and guns a re- permanent fortification. In bastion forts the sides doubt which is constructed can contain:-Com- should not be less than 100, nor more than 200 pute the area in square feet of the surface con- yards, that the flanked parts may be within tained between the foot of the slopes of the musket shot : 130 yards is a good medium. The banquettes, and divide it by ten if no artillery is best form of the curtain is to break it twice, by to be placed in the redoubt; the quotient will which a very advantageous fire is obtained. give the number of men that can be lodged in Têtes de pont are thrown up for covering a the work : but, should the redoubt be supplied communication across a river, and favoring the with cannon, subtract 324 square feet for each movements of an army or detachment, either piece from the above area, and divide the re- when advancing into the enemy's country, or mainder by ten, which will give the number of retreating from it. The form, size, and strength men.
of a tête de pont, ought to be regulated accordOf fortins or field-forts.-Two kinds of fortins ing to various circumstances, and before you fix or field-forts are most generally used, when the upon them it is necessary to consider; 1. 'The ground, the intended object of the work you importance of the communication which it is to have to construct, and the strength of its detach- cover, and the probable length of time, during ment, will allow you to make it regular, or nearly which the communication is to be kept up; for 50; these are the forts with tenailles or star-forts, its utility may be confined to a temporary moveand the forts with bastions; but sometimes you ment of the troops, or extended to the sequel of are compelled to construct a fort which is com- operations for a long time: 2. The breadth and posed of different figures at once, and in this form of the river at the point where the tête de case no particular name can be given to it. pont is to be thrown up ; and, likewise, the
Field-forts take a particular name also from nature of the country on both banks : 3. Wbetheir number of saliants; thus, a fort is said to ther the tête de pont can be supported by musbe square, pentagonal, or hexagonal, &c., ac- ketry from the opposite banks, or by artillery only, cording as it has four, fire, or six saliants. or by neither; 4. Whether the river has only one
Star forts, or forts à tenaille, are such as form arm, or forms an island ; and in this case, what a regular suite of saliant and re-entering angles. is the breadth of its arms, and the form of the They are, in fact, polygons, whose sides are ground in the island itself, so that you may broken so as to form the re-entering angles. If determine, with more certainty, the defensive possible, the saliant angles should never be less dispositions which can be made to the greatest than seventy degrees, and the nearer they aj adsantise: 5. When you are to construct a tête proach to ninety the better, its a rectangular de pont for covering the retreat of an army, or defence is always the best. The brisures, or strong detachment, you ought to consider, whefaces, forming the re-entering angle, should not iher, according to their composition and the be less than fifty feet, or more than 100. If they state of things, that retreat is likely to be exeare longer they require a numerous garrison cuted with celerity or slowness; whether there to defend them, and it would therefore be better, is any fear that the retreating troops will be