secure anchoring ground in the bay. The countries along | latter with respect to the curtain: by these changes a better the northern and southern shores of the Frith comprehend the most fertile and best cultivated parts of Scotland. (MacCulloch's Highlands, &c.; Sinclair's Stat. Account.) FORTIFICATION is the art of constructing works for the protection of a town or military position.

defence was obtained from the flanks, and the evil above mentioned was diminished. But a still greater amelioration was made by Count Pagan, who, in 1645, proposed to make each flank [See the half-front of Fortification between F and G, fig. 1, BASTION] perpendicular to the produced face of The principles which regulate the general plan of the the collateral bastion: the reciprocal defence which the works constituting the fortifications of a town or great mili-works should afford each other is thus complete, and the tary post, have at all times been nearly the same. Among men are not in danger of being fired on by each other. the antients, with scarcely any exception, the polygonal Pagan retains the orillons at the shoulders of the bastions, wall surrounding a place was provided with towers project- and he gives to the latter double or triple flanks; but the ing from it at intervals towards the front; and a barbacan, construction of these, on account of their numerous inconor outwork, consisting of two or more towers, connected by veniences, has ever since been discontinued. walls like those of the fortress itself, was generally con- During the reign of Louis XIV. a general reparation or structed on the exterior side of the ditch and opposite a reconstruction of its fortresses was ordered by the French gate of the town, in order to protect that entrance and the government; and the talents of Vauban were exercised in bridge leading to it. The towers and walls about an antient devising and carrying into execution those improvements town correspond to the bastions and curtains forming the in the art of fortification which, together with the merit disenceinte of a modern fortress, and the barbacan may be con- played in the conduct of fifty-three sieges, have given that sidered as the counterpart of its ravelin, or principal outwork. engineer so much celebrity. Besides the changes made in The necessity which the nations of Europe were under of the disposition of the parts of the enceinte, the outworks remodelling their fortified towns in consequence of the were entirely remodelled; and instead of assigning, for the change produced in the art of war by the invention of gun- delineation of the plan, numerous arbitrary rules which powder, gave occasions for the engineers of Italy, France, varied with the nature of the polygon, Vauban adopted the and the Netherlands to emulate each other in devising the length of the side of the polygon as a base, and took certain most advantageous methods of disposing the works for the aliquot parts of this line for the dimensions of the several purposes of defence with relation to the arms then newly divisions of the rampart; thus reducing the construction to introduced; and the result of their labours was the con- a few simple precepts which were applicable to places of all struction of numerous strong fortresses on the frontiers of magnitudes. These precepts being founded on the uses of the those countries. In these the bastion system, as it is called, works may be justly considered as constituting a system of was invariably adopted; and it is remarkable that, of the fortification; and from that time to the present scarcely any very numerous projects which have been since offered to deviations have been made from them in the construction the world for fortifying places, so few should have been of of great fortresses. A brief outline of the system will therea different kind. The variations however which occurred fore be here given. [See the half-front of fortification in the details of the plans gave rise to the denominations of between G and E, fig. 1, BASTION.] the Italian, the French, the Spanish, and the Dutch methods, in speaking of the works proposed or executed at the end of the sixteenth and the beginning of the seventeenth centuries; but it must be observed that those variations consisted chiefly in the magnitude of the angle which the two faces of a bastion made with each other, and in the extent of what was called the second flank; that is, the portion of the curtain then generally left between the flank of a bastion and the place where the produced face of the collateral bastion intersected the curtain.

The first bastioned fortresses of France appear to have been very inferior to those which were executed in the Netherlands by the Italian engineers; and there still exist some remains of these last in which the bastions are sufficiently capacious, and at distances from each other within the effective range of musket-shot. The others, on the contrary, were characterized by small bastions, scarcely capable of receiving artillery, and placed so far asunder as to defend each other very imperfectly. But after the termination of the civil wars which desolated the country, the attention of the French government was directed to the state of the military posts; and Errard, a member of the corps of engineers then instituted, was appointed to superintend the reparation of the old, and the construction of the new fortifications. The citadel of Amiens was built according to the plan proposed by this officer, who, in 1594, published a treatise on fortification, in which some effort is made to determine the principles which should regulate the forms and dimensions of the works.

In the method proposed by Errard the bastions are much larger than those of the earlier time, the length of their faces being, as at present, about one-third of the distance between the salient angles of two collateral bastions; an orillon occupied nearly two-thirds of the length of each flank, which was very short, and formed an angle of about 80° with the curtain. This direction appears to have been given to the flanks in order that the guns behind their parapets might be as much as possible concealed from the view of the enemy in his counter-battery; but it is evident that the defenders of the opposite flanks, laying their muskets perpendicularly to the lengths of the parapets, according to the general practice, would almost inevitably fire upon each other, or upon those who were stationed on the curtain.

De Ville, who composed a treatise on fortification in 1629, made several improvements on the method proposed by Errard, the principal of which were an augmentation of the length of the flanks and a perpendicular direction of the

The length of each side, as FE, of a regular polygon supposed to surround the town or position, is made equal to 360 yards, in order that all the parts of the rampart on each front of the enceinte might be within the range of the arms employed in the defence. Those arms are generally large muskets, whose point-blanc range is estimated at about 300 yards. Now these being supposed to be placed on the flanks, as at e or f, might be employed to oppose the formation of the counter-battery at H, or at the corresponding point on the left of F therefore, if we assume the length of the line from e to H to be 300 yards, and deduct from it the estimated breadth of the main ditch and coveredway (40 yards), we have 260 yards for the length of e E or f F, which is called the line of defence. This is also the distance of E or F from the shoulder of the collateral bastion; and if we add to it the length of the face of the bastion, which is 103 yards, or two-sevenths of EF, in order that, in the inferior polygons, the bastion may have sufficient capacity, we obtain about 360 yards for the distance between the salient points F and E of the two bastions; and it may be observed, that a few yards more or less in the dimensions need not be regarded.

The directions of the faces of the bastions on each front coincide with lines drawn from the angles E and F of the polygon, through the extremity of a perpendicular let fall from the middle of the line EF and made equal to onesixth of that line; and each flank is the chord of an arc, described either from the opposite angle E or F of the polygon, or from the nearest shoulder of the collateral bastion, as a centre. By this construction the flank is rather greater in length than the enemy's counter-battery, which is necessarily limited by the angle of the glacis and the prolonged face of the nearest bastion; and it is nearly perpendicular to the direction of that face: the reason why it is not made exactly so is, that a man on the flank, placing his musket perpendicularly to the line of parapet, will thus be able to fire into and defend a breach which may be made in the face of the collateral bastion. The curtain is determined by a line joining the interior extremities, near e and f of the flanks; and, with the height which Vauban assigned to the rampart of the enceinte, this length will permit the fire of musketry from each flank to defend the opposite half of the ditch between the flanks. The line which on the plan indicates the directions of the faces, flanks, &c., of the works, is called the magistral line; it forms the exterior side of the ramparts in fig. 1 [BASTION], and coincides with the cordon, or projection, at the top of the revetment N, fig. 2.

The dimensions of the ditch are determined by the necessity of obtaining from it the earth for the formation of the ramparts and parapets, care being taken that it be not so wide as to allow the enemy, from a battery situated as at K, fig. 1, on the crest of the glacis, to see, and consequently to batter, the escarp wall near the foot of the latter. [BREACH.] The counterscarp wall is rounded opposite the flanked angles at E or F, and from thence tends towards the shoulder of the collateral bastion.

The improvements made by Vauban in the ravelin are described under that word: Q represents one-half of that work; and it will be necessary here to say, merely, that its plan is determined by using the angular points near e and f, formed by the magistral lines of the flanks and curtain, as centres, and with radii equal to the distances from thence to points taken on the faces of the collateral bastions, at 10 yards from their shoulders, describing arcs; the intersection of these arcs determines the salient angle of the ravelin; the magistral lines of its faces tend from that intersection to the points just mentioned, and terminate on the counterscarp of the main ditch.

The traverses in the covered way were proposed by Vauban, in order to diminish the effect of the ricochet; and he was the first engineer who formed the spacious places of arms, as they are called, at L, in the re-entering parts of the covered-way, in order to obtain room for assembling troops, and to afford a good crossing fire of musketry from their faces for the defence of the glacis in front of the bastions and ravelins.

An attention to the reliefs of the several ramparts of a fortress is no less necessary than to the plans; for, as it would be advantageous, when the approaches of the besiegers are near the foot of the glacis, that a fire of artillery should be made from the ramparts of the enceinte or ravelin, and of musketry from the covered-way at the same time, the reliefs of those ramparts should be determined by imagining a line to be drawn from the foot of the glacis through a point three or four feet vertically above the crest of the latter, that is about 11 feet above the ground, and to be produced through the parapet of the said enceinte of ravelin; then, if the soles of the embrasures, which are necessarily 4 feet below the crest of the parapet, be made to coincide with such imaginary line, the fire of artillery from them may be directed to the enemy's trenches without incommoding the defenders of the covered-way. The crest of the enceinte thus determined will be about 18 feet above the ground, and that of the ravelin about 3 feet less.

The tenaille, P, fig. 1, [BASTION,] will be described under that word; but it may be mentioned here that the relief of this work is determined by the consideration that, while it should be high enough to mask the postern in the curtain behind it, the men stationed on it to defend the ditch should be below the lines of fire from the flank of one bastion, when directed to the foot of a breach supposed to be made near the shoulder of that which is collateral to it, in order that they may not be injured by that fire.

As Vauban had occasionally to adapt works constructed according to the principles above mentioned, to the old fortifications which then existed, the particular method employed in disposing them acquired the denomination of his second system; and when, subsequently, he fortified Neu Brisach, some few modifications which he was led to make gave rise to a new distinction, the works of that place being considered as forming a third system. In both these systems the bastions V, fig. 3, [BASTION] are separated by a ditch from the enceinte; and this circumstance is so far advantageous, that the place would not be compelled to surrender immediately upon those works being taken by the besiegers. The enceinte consists of a long curtain, either quite straight or broken by two short flanks; and at the angles of the polygon are small bastion-towers of masonry (T, fig. 3), in whose flanks are formed casemates to contain artillery for the defence of its ditch. engineer died in 1707, at the age of 74 years; and, from his time, the French fortification has been that of all Europe.

This great

It would be improper in this place to omit the name of Coehorn, who was a contemporary of Vauban, and who is also distinguished by the invention of three methods of fortifying places; of which however the first only, and that partially, has been put in execution. The outline of the plan differs but little from that of his rival's first system, but the shoulders of the bastions are strengthened by large

towers, or orillons, containing casemates. In the interior of each bastion is another, on a higher level, and on the exterior is a counterguard, or detached work, consisting of two faces. A large ravelin, inclosing a smaller one on a higher level, is placed before the curtain, and the whole is surrounded by a broad covered-way, whose places of arms are retrenched by brick redoubts. The ditches are full of water; and the terrepleins, as well of the bastions and ravelins as of the covered-way, are sunk below the natural surface of the ground, so that it would be impossible, in the marshy soil on which the fortifications are supposed to be constructed, for an enemy to dig trenches there in order to form covered approaches. The terrepleins of the principal works are also well defended by fire from the covered galleries which cross them, or which are formed within the masses of the ramparts.

It should be observed that the salient points E, F, &c., of the bastions and ravelins in Vauban's system being nearly equally distant from the centre of the place, the trench executed by the besiegers to connect the glacis before the former works will also connect that which is before the latter; and that, in consequence of this construction, breaches may be formed, and assaults made, at one time, in the enceinte and outworks. With the view, therefore, of preserving the former untouched till some time after the ravelins may have been taken, the French engineer Cormontaingne proposed, about 30 years after the death of Vauban, to advance the salient points of the ravelins as much as possible, by increasing the length of the faces to the utmost limit which a regard to the due magnitude of the flanked angle will admit. Thus the magistral line of his ravelin is determined by the sides of a triangle whose base is a line joining two points on the faces of the collateral bastions, at 30 yards from the shoulders, and whose opposite angle is equal to about 70 degrees. By this construction it would become impossible for an enemy to crown the glacis of a bastion till he had got possession of the two collateral ravelins, on account of the fire which, from these, might be made upon his approaches between them; and the fall of the place would be delayed by the time spent in conducting the approaches from the ravelins to the intermediate bastion.

In order that this benefit might be obtained in the highest degree, Cormontaingne suggested the propriety of fortifying places on polygons of the superior kind, and even, when possible, of constructing two or more fronts of fortification on one straight line; this practice would have the additional advantage of rendering the flanked angles of the bastions very obtuse, by which, not only would the increased capacity of those works permit stronger retrenchments to be formed in them, but the faces being produced outwards, would tend to points on the faces of the ravelins, and thus would be completely secured from the enfilading fires of the besiegers.

Besides the above general modifications, Cormontaingne made several improvements in the details of the works. He made the flanks exactly perpendicular to the prolonged faces of the collateral bastions, for the sake of a more complete flanking defence. He made the terrepleins of the ravelins merely wide enough to contain the artillery of the defenders; in order to increase the capacity of the redoubt in the ravelin, and to deprive the enemy of the space necessary for a battery on the ravelin, by which he might breach that redoubt. He also gave large casemated flanks to the latter work, in order that a powerful fire might be directed from them against the enemy, if he should attempt to mount the breach in the face of either bastion before he had got possession of the redoubts as well as of the ravelins themselves. A further improvement was made by this engineer in adding to each of the re-entering places of arms a spacious redoubt, which would render the defence of that place more obstinate, and cover the passage between the tenaille and the flank of the bastion.

As early as 1640, Dillichs, in a work published at Frank fort, proposed a method of fortifying places, which consists in surrounding them by lines of rampart forming with each other a series of angles alternately salient and re-entering; and, subsequently to the time of Vauban, a few other projects of a like nature have been suggested. The most remarkable of these is that which was published in 1776 by the French General Montalembert, who entitles his method Fortification Perpendiculaire. Its outline on the plan is a series of the sides of equilateral triangles formed on those of a dodecagon inclosing the place; the re-entering angles

being consequently right angles: and, as the general has developed some useful ideas concerning the interior defence of a place, though no existing fortification affords an example of the method, a short description of it may with pro-mated tower at each extremity; and, behind the gorge of priety be given.

Three parallel ramparts of earth, of the form above indicated, and separated from one another by wet ditches, surround the place: the berme at the foot of the first and third is protected by a simple wall, and that at the foot of the middle rampart is covered by a loop-holed gallery on its whole length. Beyond the outer ditch is the coveredway, whose re-entering angles are fortified by strong redoubts. In the re-entering angles of the two interior ramparts are formed casemated batteries, the fires from which would sweep the surfaces of the ditches in front, in the directions of their lengths; and, within the enceinte of the place, a circular redoubt, or tower, of brick-work, carrying several tiers of guns, is intended to defend the interior rampart, if, at length, it should be forced. The merit of this system is supposed to consist chiefly in the powerful fire which the casemates would afford, as from their situation, they would scarcely be injured by the enemy; in the difficulty which the latter would experience in getting over the detached walls; and in the great force which the defenders, by means of the spacious communications, might bring up to oppose the assailants.

During the existence of the French empire, the celebrated Carnot proposed to restore the balance between the attack and defence of fortresses, which the inventions of Vauban had made to preponderate greatly in favour of the former, by means of powerful sorties from the place and an abundant discharge of stones and balls from mortars fired at considerable angles of elevation; thus annoying the besiegers in their trenches, and either putting great numbers of their men hors de combat, or compelling them to recur to the slow process of blinding their approaches. Adopting, in his method of fortifying places, the proportions of Cormontaingne for the plan of his bastions, but making the whole length of his front of fortification equal to 480 yards, he detached the bastions from the enceinte, which he made

to consist of a simple polygonal rampart of earth. In rear of the tenaille between the bastions he placed a faussebraye, whose exterior side was to be protected by a caseeach bastion, he formed a row of casemate vaults, in which the mortars were to be placed for throwing stones, &c. into that work when gained by the enemy. Adopting also the ideas of Montalembert respecting detached walls, he proposed to surround the enceinte by one, which was to be loop-holed in order that a fire of musketry might be made from it, and to construct a similar wall before the faces and flanks of the bastions. The bastions were to be covered by narrow counterguards; a cavalier, or lofty redoubt, in front of the tenaille, was to defend the collateral faces of both bastions and counterguards; large ravelins were to cover the central parts of the fronts of fortification and afford crossing fires on the ground before the bastions; while mortars placed on the faces of the work and on the barbettes at the angles were to discharge their missiles over the parapets. A ditch surrounds the whole, and its exterior side is made with a gentle slope from the bottom to the level of the natural ground in front, for the purpose of facilitating the sorties; the corresponding facility which the enemy might have for descending into the ditch being disregarded on account of the supposed impossibility of maintaining himself there under the hail of stones and shot from the works.

It was supposed that the detached wall, being covered as before mentioned, would present an impassable obstacle to the assailants; but an experiment made at Woolwich in 1824 has proved the possibility of breaching it by a fire of shot and shells, directed over the parapet of the counterguard, from artillery of great calibre, at the distance of 400 yards from the latter work. The efficiency of the vertical fire, as it is called, of stones and shot from the works has also been controverted; and experiments have been made which seem to prove that the momentum acquired by the missiles in their descent would not be sufficient to do serious injury to a man on whom they might fall, if he were protected by a proper head-piece. Plan of a Front of Fortification according to the Method of Cormontaingne.

LL, Re-entering places of A, Solid Bastion. B, Hollow ditto. X, Retrencament. P. Tenaille. G, Caponniere. QQ, Ravelin, Y, Redoubt in ditto. Arms. WW, Redoubts in ditto. RR, Covered-way. tt, Traverses. SS, Glacis. Z, Barbette battery., VOL. X.-3 C P. C., No. 642.

For the works occasionally constructed beyond the glacis of a fortress, see FLECHE, HORN-WORK, LUNETTES, and FORUM, a large open space in antient Roman cities TENAILLONS. (corresponding to the Agora of the Greeks), usually surOf the works which fall under the denomination of field-rounded with public buildings, where the citizens met to fortifications, BRIDGE-HEADS have been already mentioned. transact business, and where, previous to the erection of REDANS, REDOUBTS, and STAR-FORTS are described un- Basilicæ, causes were tried. From this last circumstance der those words; and the combinations of works which the word forum is used metaphorically for a place of justice. serve for the protection of armies, under LINES OF EN- Nardini is of opinion, though without any show of authoTRENCHMENT. Small forts with bastions are frequently rity, that the first forum, or Forum Romanum, at Rome, considered as field-fortifications: their plan is similar to was placed on the Palatine hill. The Greeks made their that of the enceinte of a fortress; but they differ from the Agora square, with a double colonnade, or ambulatory, above latter in their size, in having low relief, and in the sides of and below, but in Italy the width of the forum was made their ditches being unreveted, or only faced with sods. less than the length by a third, and the columns set wide apart, as the gladiatorial shows were formerly given in the forum. (Vitruvius, lib. v., 1.) The Roman fora were of two kinds, Fora Civilia and Venalia: the former were for law and political affairs, the latter for the purposes of trade. Rome contained nineteen fora of importancethe Forum Antonini, Archemorium, Argentarium, Au

gusti, Boarium, Cæsaris, Cupidinis, Nerve, Olitorium, J Stator, still remain. Nardini places on the side of the PaPiscarium, Piscatorium, Pistorium, Romanum, Sallustii, latine hill, in succession, the Fabian arch, Græcostasis, SenaSuarium, Tauri, Trajani, Transitorium, and Vespasiani. lum, Basilica Opimia, Edicula of Concord, Temple of RoOf these the Forum Romanum, Nervæ, Trajani, Boarium, mulus, Temple of the Dii Penates, Curia Ostilia, near which and Piscatorium, alone retain any traces of the splendid was the Comitium, Basilica Portia, Temples of Julius Cæsar, edifices with which they were once adorned. The Forum and Castor and Pollux. On the side towards the Tiber stood Romanum is situated in a narrow valley, not far from the the Temples of Jupiter Stator, Temple and Atrium of Vesta, Tiber, between the Palatine and Capitoline hills. It sweeps Basilica Julia, house of Lucius Tarquinius, and the Temple round towards the Fora of Cæsar and Augustus, which are of Victory. On the side of the capitol was the arch of between it and the larger Fora of Nerva and Trajan, all Tiberius, the temples of Saturn, of Concord, and of Vespawhich, looking at their relative situations, were, no doubt, sian, the school of Xanthus, the arch of Severus, which still connected with it on the north. On the south it extended remains, and the Tullian prisons. On the north side of the nearly to the Fora Boarium and Piscatorium, which were forum was the office of the secretary to the senate, and the near the Pons Palatinus, now called Ponte Rotto. The Basilica of Paulus Emilius. There are however but few reexact limits of the Forum Romanum are very uncertain; mains existing of a small number of these numerous buildNardini (vol. ii., p. 138) endeavours to point out its bounda- ings, and the greater part have entirely disappeared. A ries. It was decorated with temples, statues, basilicæ, cu- single monumental column stands near the Comitium, called riæ, rostra, triumphal columns and arches, which usurped the Column of Phocas. Besides these buildings there are the place of shops, schools, and even private houses, that remains of the temples of Fortune, Jupiter Tonans, Jupiter originally stood in this forum. In the forum were the Capitolinus, and the Tabularium, though these are perhaps rostra, or pulpits, decorated with the beaks of ships, whence not within the boundaries of the forum. (See plates in Narthe orators harangued. According to Appian the rostra dini's Rome, vol. ii. lib. v., c. 1.) A very beautiful restored were placed in the middle of the forum, and he states that view of the Forum Romanum was made by Mr. C. R. CockerSulla caused the head of young Marius to be hung up be- ell, and a reduced view was engraved and published, with fore the rostra in the middle of the forum. Varro, in his his permission, in the second volume of the Pompeii,' pubfourth book, De Lingua Latina,' places the rostra before lished by the Society for the Diffusion of Useful Knowledge, the curia, which was near the Comitium, so that the orators to which we refer our readers for an accurate notion of the would stand with their faces towards the capitol; but Plu- splendour of the accumulated architecture of the Forum and tarch, in speaking of the Gracchi, states the reverse to be the Capitol, and its vicinity.

the case.

The forum at Pompeii, which was constructed in the Greek style, cannot however be altogether considered, if we are guided by the authority of Vitruvius, a truly Greek Agora, which this author states was to be made square in form. It has however many Greek features. The Pompeian forum is of an oblong shape, surrounded on three sides with rows of columns, forming, with the advanced columns of the various buildings, a colonnade or ambulatory; above this there was a second, if we may judge from the remains of stairs at several places at the back of the colonnade. The fourth side of the forum is inclosed with two arches placed on each side of a large hypæethral temple, called the Temple of Jupiter. On the west side are the prisons and the granary, with an enclosed court before it and the prisons; the Temple of Venus and the Basilica [BASILICA]; and on the narrow side, opposite the Temple of Jupiter, are three buildings generally considered to be the Curie and Erarium: on the east side is an enclosure, the use of which has not been determined, the Chalcidicum [CHALCIDICUM], the Temple of Mercury, the Senaculum, and a building supposed to be a large eating-house, generally known by the name of the Pantheon, in front of which are the Taberna Argentaria. The enclosed area of the forum was paved with large square pieces of marble, and the sides of the area were adorned with statues. Opposite the curiae and a short way from them is a small triumphal arch. The forum was closed at night with iron-barred gates, and it does not appear that chariots were admitted into it, as the pavement of the streets terminates at the back of the colonnade. The columns of the ambulatory are of the Greek Doric order, and were being restored in the same style, though with better materials, at the time the city was destroyed. The columns were aræostyle, and the architraves were most probably of wood, as we may infer from their

1,1, Curia; 2. Eranium; 3, Chalcidicum; 4, Temple of Mercury; 5, SenacuJum; 6, Pantheon: 7. Temple of Jupiter; 8, Prison; 9, Granary; 10, Temple of Venus; 11, Basilica.

{ a, holes for the joists of the upper floor.

The Comitium was placed near the Curia; three columns of the former, commonly called the Temple of Jupiter being destroyed, while the frieze and cornice of stone re