156 MILITARY SCIENCES. 



curtain, the tenaille, and in front of this the demi-lune or ravelin, the con- 

 struction of which will be given in describing the different systems. 

 While the ravelins were made very small, works similar to tenailles were 

 placed in front of them, running parallel to their faces, and strengthening 

 them. In the same manner a work called the couvre-face, counter- guard, 

 or bastion shield, was run parallel to and lower than the bastion. Of this 

 more will be said hereafter. Works often employed in the earlier systems 

 are the horn works and crown works. One front of attack, as it is called, 

 forms a horn work ; a crown work consists of two such fronts. Both may 

 lie either before the ravelin or in front of a bastion, and are then carried 

 back to the main work by long flanks. Fig. 5 shows a horn work in front 

 of a bastion, Jig^ 8 one in front of a ravelin : H and I are the long flanks, 

 w^hich must be defended from the main work. Figs. 6, 7, are a crown work 

 before a bastion; Jigs. 11 to 16, the same before a demi-lune : G is here 

 one of the connecting flanks. Detached works are independent forts for 

 the defence of single points which cannot be brought within the region of 

 the enceinte or the outworks, and yet must be defended. They are dis- 

 posed after the manner of star forts or as open w^orks (Lunettes), and 

 communicate with the main work by means of a covered way. With 

 respect to the various systems of fortification according to which works have 

 been disposed since the 16th century, the principal of these are as follows : 



1. Gerhard von Herzogenbusch (Erard Bar le Due) was the first who 

 established fixed rules for fortification. In his system (pi. 48, Jig. 6), 

 the half bastion angle at A and B is 45®, and by setting this off* in the 

 capital for the polygon side, ah, the lines of defence, af and bd, are obtained. 

 Bisecting now the angle of the half bastion, and drawing the lines ag and 

 bh, these intersect the lines of defence in d and /, from which points the 

 perpendiculars, fe and cd, are let fall upon the faces, and these form the 

 flanks, DD, which are connected by the curtain, C. To draw the ditches, 

 F, describe, from a and b as centres, circles having the length of the flank 

 for radius, draw tangents to them from the shoulder angles c and e, which 

 intersect at E, where, in the covered way, a place of arms is disposed. 

 This system has sometimes orillons, as, for example, at Amiens. 



2. Marolais, a Dutch engineer, constructed his system (Jig. 7) for a hex- 

 agon, in the following manner, ab being the polygon side. The angle of 

 the half bastion being fixed by Marolais at 40°, make the angles abh and 

 kab = 20°, and draw the lines of defence, af and bf, which intersect at e. 

 The length of the faces ag and bi is 288 feet, and from the points g and i 

 perpendiculars, dk and ch, are drawn to the polygon side, ab. From the 

 points g and i, set off", on these perpendiculars produced indefinitely towards 

 h and k, angles of 55°, and join the points where the lines defining these 

 angles intersect the capitals, by a line ; this last parallel to the polygon side, 

 will determine the length of the flanks and form the curtain. Ditches and 

 places of arms are constructed as by Bar le Due. Marolais usually placed 

 in the ditch, which was then made wider, a faussebraye (or lower rampart), 

 which, below the main work and parallel with it, ran round the whole 

 enceinte. 



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