Gates. 
tive merits 
of wet and 
ary ditches. 
‘Caponniers. 
PLATE 
cc_Lvil. 
Fig. 3. 
Cunette. 
Bstardesux. 
Hig. 1. 
in height. They are shut by a draw-bridge, and also 
by a strong door at each extremity of the On 
the right and left of the , and within the town, are 
watch-houses for centi which ought to be shell- 
proof. Formerly, the bridges before the gates were of 
wood, but in the new fortresses they are of stone. The 
former had the advantage of being easily burned, in 
case of emergency. 
In those curtains that have no gates, there are sub- 
called posterns, which communi- 
works, The extremity next the field ought to be co- 
vered by a tenaille, or closed up by a very. gate. 
Engineers have differed in opinion with to the 
comparative merits of a dry and a wet ditch. There 
can be no doubt, that one capable of being made either 
dry or wet, according to circumstances, is to be pre- 
ferred: at the same time, it seems to be generally ad- 
mitted now, that a dry one is the -Aore etrnee cy 
particularly if the enceinte has a revetement. It not 
only enables the garrison to lend more prompt and ef- 
fectual assistance to the outworks, but it also encou- 
the defenders of these to main same A nari 
more obstinacy, knowing that they have a iy 
and safe swe oi of pros Here Besides, it is on- 
ditch that the garrison can make sorties, 
communication by means of boats being altogether 
unfit for rapid movements. 
In a dry ditch, the communication between the for- 
tress and the ravelin consists of a passage 6, Fig. 3. 
about nine feet wide, and inclosed by a on each 
side, inating in a glacis. A of kind is 
called a caponnier. When they have a only on 
one side, they are called half dupoahiensy" Both kinds 
are sometimes carried between the shoulder of the bas- 
tion and the ravelin, as well as between various other 
parts of the fortification, and are useful in defending 
the ditch. They are always perpendicular to the lines 
which they enflank. 
In moist ditches which are intended to be dry, it is 
frequently necessary to have a small ditch called a cu- 
nette, for carrying off the superfluous water. It is also 
sometimes used to prevent the enemy from surprising 
a work that has no revetement or wet ditch. “Tn thee 
case, it is 8 feet deep, and 12 wide. 
if a place be so situated, that a current of water can 
be brought through the ditch at pleasure, it gives the 
garrison a prodigious advantage over the besi ; 
obliges the latter to be very cautious 
ene tch for the purpose of making an as- 
In ‘order more effectually to inundate the ditch, 
dams-or batardeaux, a 6, c d, Fig. 1, are sometimes em- 
ployed. ‘They are constructed of stone, and of a suffis 
FORTIFICATION. 
the sl a be af prose Winans 
e sluices t to be w ' 
tardeau is constructed before the curtain, it 
communication between the and the ravelin, by 
means of a gallery in the interior, 
Tenailles are generally 50 feet in width, 
rapet on the escarpe, and a terre-plein of 25 
derneath, have posterns ‘to those in the 
rampart, in the outer extremity of which may be con- 
structed a convenient harbour t 
t of stairs. sali 
led simple when the interior | 
empty, and when they have reduits within. 
A simple Gerti-lone qoaslats 5° 9, paeee: oe eae 
part with a pet upon it. The width of this ram- 
part ought to be about 50 feet, which will leave 50 feet 
for the terre-plein, after a parapet has been constructed. 
The ramps of the terre-plein are in the saliant angle. 
Demi-lunes are sometimes furnished with posterns, 
which serve for a communication with the 
arms when the ditch is wet, and for sally ports 
the ditch is dry. erally in the 
angle. The of to have 
revetement with a small harbour, and ramps or stairs. 
The reduit of a demi-lune ought to have a ram 
of 50 feet wide, with a and ramps at the extre- 
mities of its faces. If the ditch before it be dry, it 
ought to be from 9 to 12 feet hi, 
enceinte. The stairs between 
Jiant 
not to reach to the bottom of the lowest, lest i. 
litate the attack of the enemy. The commur 
for the ison may be completed by wooden stairs, to 
trees 
formerly mentioned, with mths 
ther in the counterscarpe. To prevent the 
way from being enfiladed, the Pratis has a 
ode > ‘Traverses have in general banquettes, 
which the covered way is ded, and which are 
high as the crest of the glacis. Sometimes the ban- 
quette is carried across to the coun’ , leaving on- 
ly one at the extremity of the traverse next the 
rlacis. Th the faces of the ‘places OF uisind Mle axe 
ramps to facilitate the sorties, about 10 feet wide, and 
so steep as to prevent their being enfiladed. These 
snghe sfc thay‘ indy MO GABOONS a 
angle, where they wou too : 
passages from thie gates the glacis are from 1 
to 18 feet wide, the sides of the 
walls, and the whole 
is heing lined. wi 
so as nowhere to ex- 
pose the covered way. .* 
brine 
£ 
Simple 
dood to 
F 
part Dimension 
of reduits. 
