160 MILITARY SCIENCES. 



and A c, are 450 feet long. From the points c and D the lines of defence 

 are drawn to k and /, and, with c A: as radius, the arcs k H and / G 

 described, from c and D, which form the flanks (usually drawn straight, 

 however), and determine the shoulder-points, at the same time, at G and H ; 

 the curtain is then k I. In front of this lies a species of tenaille, which 

 Cohorn called the low curtain, and which is drawn by describing from c 

 and D, with a radius of 840 feet, the arcs o E and p F between the lines 

 of defence, and thus obtaining the flanks ; the faces, F H and E G, are then 

 determined necessarily, and the curtain, o N jo, is broken in the direction of 

 the lines of defence. In the shoulder angles of the bastion, Cohorn placed 

 casemated orillons, the details of which are shown in fig. 25 : '• '^' ^ are the 

 casemates, and at A z and z y are loopholes and embrasures for the defence 

 of the ditch ; a aa are vaulted buttresses. The orillon has its own small 

 wet ditch, F, which is filled from the main ditch and over which lead the 

 bridges, h z, to the orillon, and g s, to the dry ditch of the lower face and 

 curtain. The parts of the enceinte hitherto described {fig. 10) form the 

 lower work, only the curtain, Ik, lies on a level with the (presently to be 

 described) upper work. To obtain this, describe, between the lines of 

 defence, from c and D as centres, the upper flanks S M and R L, with a 

 radius which is obtained by drawing a line parallel to the face of the bastion 

 and 124 feet from it ; the point where this intersects the opposite line of 

 defence determines the radius C S or D R ; afterwards the curtain receives 

 the breaks, k U and I T, in the direction of the lines of defence ; the terre- 

 plein between the upper and lower fronts is dry, only in front of the low 

 flanks and the orillons is the ditch wet. In the terreplein, palisades are set 

 before the faces. The ditch runs with a breadth of 144 feet parallel with 

 the faces of the enceinte. To draw the ravelin W, lay oflT, from the point 

 where the counterscarps of the main ditch intersect, 33u feet towards W ; 

 then, on each side of the capital, lay off" an angle of 35°, which determines 

 the direction of the ravelin faces ; they are produced to the counterscarp. 

 Within the ravelin lies the redoubt XYZ, parallel to it at 136 feet distance. 

 In the terreplein of the redoubt a second redoubt is formed of palisades ; in 

 the dry ditch, also, in front of the redoubt, palisades are placed. D' is a 

 salient place-of-arms of the covered way ; A', a re-entering ; and these are 

 defended in a peculiar manner, first, by the traverses, C, and a double 

 glacis, and again by the palisaded redoubts, B' (coffres). Cohorn has 

 permitted some changes here and there in this system, so that a second and 

 third system are recognised, but these changes are not important. 



10. Herbort, the engineer of Duke Charles Alexander of Wirtemburg, 

 has, in his system (pi. 48, fig. 9), retained the bastions, but introduced 

 extensively crenelled galleries (galleries with loopholes). In the interior 

 of the bastions, A, are found the redoubts, B, provided with crenelled galleries 

 having earthen parapets above, which are separated from the broken cur- 

 lain, nop, serving for casernes, and likewise casemated, loopholed, and 

 having an earthen parapet above. The curtain is flanked by two redoubts, 

 q q, casemated, and covered with earthen parapets. The bastion orillons 

 of the enceinte, hfega, lie somewhat higher than these redoubts, are case- 

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