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i faces of the ravelin termi- 
nate on those of the bastion $0 feet from the shoulder. 
The object in both cases is to 
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to be as acute as is consistent with the best 
defence. In Vauban’s method, this angle is always ob- 
of the ravelin’ was at first equal to 
side of the polygon. Finding, how- 
shoulders were very much exposed, 
‘he enlarged the angle by extending the faces of the 
in con- 
structing re- 
chuits, 
in the oo- 
ravelin to one third of the side of the polygon, and ma- 
terminate on the faces of the bastion 90 
feet from the shoulders. He sometimes also used flanks 
to his ravelin as op, epee — two sere 
taking gp equal to 42 feet, and po to 60. ese 
flanks, : ever, are of little use, as they are easily en- 
filaded by the enemy, and afford little protection to the: 
tain. 
Formerly the faces of the ravelin terminated on the 
counterscarpe of the ditch, in the re-entering angle of 
which a small harbour was constructed for the boats 
that were used to keep up the communication between 
the ravelin and the In this form, however, the 
back part was found to’be easily enfiladed, and now the 
faces terminate on the lines Am, Bn, drawn from the sa- 
liant angles of the bastion to the end of the terre-plein. 
As an inducement to hold out in defending the ra- 
velin, which is too frequently given up without neces- 
sity, Vauban constructed reduits within the ravelin. 
These consisted at first of a single wall, two feet thick, 
and from six to seven feet high, and were intended to 
cover the garrison in retreating from the demi-lune in 
case the latter were taken. were of the same 
form as the demi-lune, their faces being 80 to 120 feet, 
and their flanks, where the ports were, 30 to 48 feet. 
They were Teo from the terre-plein of the demi- 
lune by a ditch 12 to 16 feet wide. 
When large demi-lunes were invented, reduits were 
converted into second demi-lunes, having faces 100 to 
feet, and separated from the first by a fossé. This 
has found very useful in defending the 
as the passage of the ditch. The width 
of the ditch before the curtain is from 100 to 130 feet, 
round the bastion 100 to 110, and before the ravelin 
. The saliant parts of all ditches are circular, 
described from the saliant angle of the work with a ra- 
dius equal to the width of the ditch. 
with faces from 72 to 100 feet, and forming an angle 
with the covered way of 100 
— traverses Ses rare the covered way, 
w being enfiladed, and 
Semel cibaebtss thesoho ree dthomegta The 
traverses were perpendicular to the counterscarpe, and 
FORTIFICATION: 
distant from each other. | 
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apeehae 
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u e principal of these 
duit D, of which the faces rea ee rere 
tuse angle, and the flank v, prevented 
covered wag tolsitd fecin: bbs eiaiadeds 
also to take th in the na Enamel 
serve to take the enemy in the rear w! 
ing to ascend the breach in the demi-lune, 
velins might be still farther improved, 
ee eee faces ; but ved 
as that angle ought never to exceed 60 degrees, the the 
most advantageous form for a ravelin, is an equilateral 
triangle. The advantages of the ravelin, however, de- 
pend not a little on the angle of the -poly; The 
angle is, the farther will the ravelins extend 
andi for the illustration of-whidii Weanechiellyinduted 
to St Paul, the in of the French for- 
tresses. We say illustration, for the discovery, we be- 
particular 
a is due to Montalembert and Belidor, 
tter. ‘ : : 
The practice of enlarging the angle of the polygon 
has been by Et Pe engineers, not ‘only 
from the advan’ ition which it gives to the 
demi-lune, but because it is found to form the 
chief merit of the modern system of defence. on 
aw 
In Montalembert’s method there are no bastions, but: Montalem- 
angles; the former 60 bert’s me- 
and the latter 90 degrees. His lines of defence,. that’ thod. 
merely saliant and re-entering 
is the lines containing the angles, are from 800 to 550) 
eet, 4 
In the preceding part of this article, we have: con- Thickness 
sidered the trace merely as a suite of lines, without re- of the diffe’ 
gard to the thickness of the works which these lines re~' Tent works. 
present. We shall now proceed to lay down the di- 
mensions of Lae aR aT at been de- 
termined by the most skilful engineers. | 
The terre-plein of the rampart 
breadth as to permit the soldiers to manceuvre, and ef- 
fectually to resist all attempts to make a breach in it, 
at the same time if it be too wide, it is much exposed 
to the enemy’s fire, occupies more than can be 
spared from the other works, and ex~. 
pensive. . By some old engi it was fixed at from 
55 to 70 feet, a breadth impracticable, and in all: 
quantity of artillery be very small, guns seldom 
require to be removed from one place to another, thi 
x ara ein A piece of ordnance after being 
ged, recoils from 18 to 25 feet, according to its: 
calibre and the nature of its mounting. The breadth 
of the terre-plein, therefore, cannot be less than from 
ub 
ought to be of such @ Rampart 
