« НазадПродовжити »
Behind the lower parapet there is a banquette coffers 9 of eight feet broad, made with planks of three feet, and a rampart of five; and under at the sides, and above with a foot of earth over this rampart a stone gallery, which runs from and before them. one end to the other, and is divided into several There are two banquettes all round the covert apartments, which are shut with doors; as like- way, and before the traverses; as also two rows wise another, going from the saliant angle of the of palisades before the traverses, one of which lower faces, to that of the higher, with loop-holes joins thein, and the other goes round the covertfrom distance to distance facing the dry ditch; way. there is likewise a row of palisades placed pa- Lastly, the re-entering angles of the counrallel to the bigher faces, and at four toises dis- terscarp next to the covert-way are made a little tant from them.
round as likewise that in the ravelin : but the There are three embrasures in Or, as has been contrary way, that is, they are made hollow. said, to Hank the ditch a behind the towers; and His Second System he adapts to a heptago: two in () to flank the dry ditch near the higher whose interior side is 126 toises, and the level of faces.
the ground to be three feet above the surface of The great ditch is twenty-four toises broad; the water. and its counterscarp parallel to the lower faces Let, therefore, the interior side, AB plate IV. of the bastions; the semi-gorges 0 L of the rave- fig. 3, of an heptagon be 126 toises; take in the lin are twenty-nine toises, and the faces LP, capitals, AC, BD, each of seventy-two toises; forty-tive; the dry ditch Y is sixteen toises, the at the extremities C, D, make the angles ACE, rampart twenty-eight feet, and the lower faces BDF, each of forty degrees; and set off sixtya T are parallel to the higher ones; the parapet six toises for the faces C E, DF, of the bastions; of which is twenty and the banquette three. on the interior side, take AG, BH, each of thirty
The level ground of the rampart in the ravelin toises, and from the point D, as centre, describe near the saliant angle is twenty feet broad, for an arc through the point G, on which set off the length of twenty toises from that angle, and a chord of thirty; and on this chord describe the rest but fifteen.
the mean flank GI, which is an arc of sixty In the gorge of the ravelin is a small redoubt degrees. 4, of about five feet high, and underneath a lodg- Draw a line from the saliant angle D through ment of stones, the walls being eighteen inches the extremity I of this flank, on which take I a thick at the sides; the roof is made of planks, of ten toises; join a E, on which describe the with three feet of earth over them.
orillon as usual. There is a dry ditch going from the extremities The outline of the higher flank is thirteen of the faces to the redoubt, and round its angle, toises distant from that of the outline of the having a row of palisades before it, to secure the mean; this flank is an arc described from the retreat from the ravelin into this redoubt; there is the same centre as that of the former, the chord likewise another row going from the extremities of which is forty toises. of the faces, in a round form, turning towards the From the points G, H, draw the broken parts gorge of the ravelin.
of the curtain, perpendicular to the capital of the In the dry ditch of the ravelin, within six toises bastion, and make it nine toises long; the extrefrom the great ditch, is a coffer, and a ditch p of mity of the higher flank is terminated by the insix toises before it: this cofier has a wall on side line of the parapet of the curtain produced. both sides, and the roof is planked and covered The tenaille is found by producing the faces with a foot and a half of earth; above this is a of the bastions ten toises ; through the extremity stone parapet of five feet high, with a banquette of which an arc is described from the opposite behind it.
saliant angle of the bastion, as centre; on this There runs a covered gallery under the ram- arc is set off a chord of twenty toises; and this part of the lower faces, and another joining the chord serves to describe the flank, upon which two saliant angles, together with a row of pali- is an arc of sixty degrees; the curtain is a right sades, in the same manner as in the dry ditch be- line. fore the bastions.
There is a wet ditch before the tenailles of The wet ditch before the ravelin is eighteen en toises broad, with two bridges at each end, toises; the counterguards x, which the author near the orillons; the one directly over it, and calls cover-faces, are twenty-five feet broad, and the other along the faces of the bastion. the ditch before them fourteen toises; the covert- The dry ditch round the body of the place is way is twelve toises broad, and the glacis twenty; twenty toises broad, before the faces of the basthe semi-gorges fg,gh, of the places of arms, are tion to which it is parallel, and the lower ramtwenty-two toises, and are taken from the point part, K L, twenty-nine feet; the semi-gorges ML g, where the branches of the covert-way meet,
are fifteen toises, and the flanks L N eighi ten, and the faces f k, hk, are twenty-eight; within and are described from the saliant angles K of these places of arms are traverses of twenty feet the lower faces as centres. thick and eighteen toises long, within ten or The saliant angle of the ravelin is 125 toises twelve feet from, and parallel to the faces. distant from the curtain of the body of the place,
The stone lodgments b, within the places and is seventy degrees; the faces are fifty of arms, are found by setting off twelve toises toises long; the faces of the redoubt .r are sixteen from the point e, for the semi-gorges, and the toises distant from those of the ravelin, and fourfaces are drawn parallel to those of the places teen long. of arms
The wet ditch round the lower faces of the At six toises from the places of arms are ravelin is twenty-four toises broad : the work len
yond this ditch, which the author calls the difficult; the arrangement of the system in second counterscary, is twenty, parallel to the question also has the inconvenience of occasionditch.
ing several openings to be left, through which the To find the broken part of this work, join the besieger can see the exterior works and the body two re-entering angles, m,r; on which take 'm r of the place from the crowning of the covert-way. of thirty toises, and draw r t, r v, parallel to the Therefore, all engineers coincide in their opinion outline of the counterscarp, each equal to twelve; that it is inferior to the first system, and conse- set off twenty-two from i to s, and from v toq; quently to the second. and upon these lines as chords describe the round We shall not therefore detain the reader by a Aanks, which are arcs of sixty degrees.
more particular description of it. The traverses in this counterscarp are drawn
Sect. IV.-CORMONTAINGNE'S SYSTEM. at ten toises from the flanks perpendicular to the parapet.
This is, in fact, with some modifications, the The redoubt %, in the re-entering angles, are modern bastion system of fortification. Upon found by setting off sixteen toises from the points Vauban's first or general system, this able engim to n, for their capitals, and the faces are neer suggested the improvement, first of a much parallel to the broken curtain before them; those greater projection which he allowed to the rave. marked y, which are in the saliant angles, are lins, whereby he considerably augmented their found by producing the counterscarps of the action upon the attacks. Secondly, of congreat ditch, and setting off twelve toises from the structing the ravelins without flanks, and dipoints of their intersections for their faces; and recting their faces to a smaller distance from the flanks are drawn parallel to their capitals. the flanked angles of the bastions, by which he
The ditch before this work is fourteen toises; covered the shoulders of these works still more as to the covert-way and glacis, they are the same effectually than Vauban had done, as well as the as in the author's first method.
curtains, and the openings between the flanks of Coehorn applies his third system to an octa- the bastions and the profiles of the tenailles. gon, and supposes the level of the water to be Thirdly, Cormontaingne's redoubts in the ravefive feet below the horizontal ground. The ex- lins are better contrived than those of Vauban, terior works of this system, that is, the detached and answer purposes much more important; bastions and the counterguards, ravelins, covert- whilst the larger size of his re-entering places of ways, &c., alone present the same arrangement arms renders them also more beneficial to the as that of the whole first system ; with the ex- defence, and particularly on account of their ception, however, that independently of the de- substantial redoubts, which, besides the other tached bastions being not joined together by any material advantages derived from them, have curtains, they only have double flanks instead of their faces so disposed as to secure them from treble ones. Each of these bastions also has a enfilade, and allow their fire to have a direction redoubt at its gorge, with a dry ditch in front and close and nearly parallel to the prolongations o a crenelled gallery adapted to the counterscarp the capitals. This advantage, which none of of this ditch. There is likewise a dry ditch be- Vauban's systems afford, is so much more imporfore the redoubt at the gorge of every capital tant as the besieger generally advances in the diravelin, which ditch is connected with the faces rection of the capitals. Cormontaingne likewise of the ravelin, as the dotted lines show, by means concealed the masonry of all the revetments of of coupures made in the direction of the coffers the place from the view of the besieger previous between the capital and the lower ravelins, or to his gaining the glacis, and thereby secured it nearly in that direction. Besides, in addition to from the fire of his more distant batteries. the coffers in front of the re-entering places of Lastly, this 'engineer much improved the commuarms, Coehorn constructs a crenelled gallery nications, although not to such a degree as along the faces of these works, on which account would be requisite for attacking the besieger to the palisades in this part of the covert-way advantage, in the works which he may have taken are to be two toises distant from the crest of the so as to drive him out of them. glacis.
Independently of the above improvements, Behind the exterior works above mentioned is which Cormontaingne has made in Vauban's the body of the place, consisting of bastions with First System, he also illustrated the superior common orillons, a revetment, and double flanks. properties that a fortification acquires, from the The curtains which connect the lower flanks are exterior sides of the fronts which compose'it either broken as in the first system, and at each of forming very obtuse angles with each other, or their extremities, between them and the principal being all in the same straight line. curtains, a kind of harbour is constructed, by To describe Cormontaingne's system, with means of which, as well as of vaulted passages such alterations as have been since suggested and made under the lower curtains, the garrison is are at present most generally adopted, proceed able to keep up a communication with the exte- as follows:rior works. There is also a kind of circular har- The length of the exterior side being at least bour at the gorge of these works.
130 toises, but not exceeding 180 toises, conSome of Coehorn's dispositions in his third struct the bastions and curtains as in Vauban's system are certainly not below the high reputa- First System : with the exception, however, that tion of such an eminent engineer; but, indepen- the length of the faces AC and B D (plate V.) dently of the great labor and quantity of masonry of the bastions is to be one-third of the exterior which this system
uires, the communications side, and the direction of the Banks perpendicu. with the exterior works, across wet diiches, are lar to the lines of defence. It is here supposed