0o6 FORTIFI 
r ies ; to prevent which, and alfo to flielter the troops in 
lome me'afure from the ricochet or rebounding (hot, tra- 
verfes are thrown acrofs the covered-way, particularly on 
each fide of every place of arms, and in every branch of 
the covered-way where the length of that branch exceeds 
fifty or (ixty yards. Each traverfe is furniflied with a 
foot-bank; and a row of pallifades planted on the foot- 
bank ; and the paflage round its end lhould be furniflied 
with klinkets or doors, to fliut it up when necefiary. 
Of /ally-ways. —In the middle of fome faces of the en¬ 
tering places of arms a fally-way is made, which is a paf- 
fage cut through the parapet, or head of the glacis, to 
facilitate the Tallies of the befieged. To make fally-ways 
in the places of arms faliant would be improper; becaufe, 
as thofe places are molt liable to be firfir attacked, they 
fiiould not by any means be weakened. Thefe palfages 
are cut obliquely to the faces of the places of arms, and 
wind toward the faliant angle in fuch a manner as not to be 
eafily enfiladed or raked ; they rife gradually from the foot 
of the parapet, until they meet the flope of the glacis, at 
the difiance of feven or eight yards from its head. The 
Toads fo the town commonly pafs through thefe fally- 
ways ; every one of which fiiould be furniflied with a good 
barrier, to fliut up againft furprifes and fudden attacks. 
Of military communication. —Every out-work in a fortifi¬ 
cation fiiould have a ready and free communication pre- 
ferved for the foldiers, otlierwife they might become very 
difadvantageous to the place. Such communications are 
preferved in various other ways than by bridges, which 
are liable to be deflroyed by the enemy’s cannon. In dry 
Ioffes it is thus: from the town to the tenail, by a fub- 
terraneous way under the rampart in the middle of the 
curtain into the fofs; and riling thence by ramps or flairs, 
into the tenail: from the tenail by a fubterraneous way 
into the caponier, and thence to the ravelin, either by 
ramps, flairs, or a timber fiage : from the ravelin to the 
works beyond, the communication is continued in like 
manner ; or otlierwife a way is funk acrofs a ditch, and 
covered with a parapet next the enemy; and the way 
from the fofs to the places of arms is alio by ftairs, or by 
a timber fiage. 
Over wet Tolies the troops are conveyed by boats, or 
rafts, or by bridges about three feet wide lying nearly 
level witli the water’s edge ; but the latter are inconve¬ 
nient in the night, and much more fo when the befieged 
are obliged to q'uit the work precipitately. In the gorges 
.of ravelins arid other out-works, a fpace or paflage fix feet 
wide is left between the counterfcarp and the end of the 
rampart, which ferves for the communication between 
that work and the covered-way. 
Before fome of the faliant angles of the glacis there is 
often confiructed a kind of lunette, called an arrow. It 
confifts of a parapet and foot-bank forming two faces, 
making a faliant angle, the legs of which are parallel to 
the head of the glacis, through the ridge of which runs a 
narrow paflage to the lunette. 
The principles on which the foregoing plan of a regu¬ 
lar fortification is laid down, are lelefted and combined 
from the works of the moft diftinguiflied military archie 
tedls, and have been adopted by the moft fkilful modern 
engineers. But as the plans or fyftems of count Pagan, 
marfhal Vauban, general Coehorn, profefibrs Belidor and 
Blondel, have each their feparate and refpedlive merits, 
we have given a diftinct fedtion of each of them, in the 
Fortification Plate III. where fig. i, exhibits the plan of 
Pagan’s fyftem, which is conftrudted as follows : A A, 
half bullions. B, the* ravelin and counterguard. CC, 
tounterguards before the baftions. D, the fofs. E, the 
glacis. F G, places of arms. H H, retired flanks, a, 
the line of defence. 
Fig, 2, Vauban’s fyftem; the parts of which are as fol¬ 
low : b, angle of the bullion, or flanked angle : c, angle 
©f the ftipitlder: d, angle of the flank : e, faliant angle : 
f face of the bullion : g, tlte flank: /:, the curtain: ii, 
tenailles; kk } traverfes in the covered-way. 
CATION. 
Fig. 3, Coehorn’s fyftem ; thus explained: i, r, Con¬ 
cave flanks. 2, 2, The curtains. 3, 3, Redoubts in the 
re-entering angles. 4, 4, Traverfes. 5, 5, Stone lodg¬ 
ments. 6, 6, Rounded flanks. 7, Redoubt. 8,8, Coffers 
planked on the Tides, covered overhead with a foot of 
earth. 
Fig. 4, Belidor’s fyftem ; thus conftrudted : 11 , cava¬ 
liers. K K, rams-horns, or tenailles. L L, retrench¬ 
ments within the detached baftions. M M, circular cur¬ 
tains. N, the ravelin. P, P, lunettes, with retired bat¬ 
teries. Q, the redoubt. R, a detached redoubt, with 
an arrow and fmall traverfes, at a a. 
Fig. 5, Blondel’s fyftem : /, a retired battery : mm> lu¬ 
nettes : n, ravelin, with retired baftions: oc, orillons. 
OF IRREGULAR FORTIFICATION. 
When a town or other place is to be fortified, it often 
happens that the polygon which bell circumfcribes its 
plan, will be more or lefs irregular; and confequently 
the fortifying of that polygon will not fall exadtly under 
the rules already given for a regular fortification: it is 
therefore proper to point out the method to be purfued 
on fuch occasions. 
Let the plan of the place be circumfcribed, if pollible, 
by a polygon, the angles of which are all faliant, none 
lefs than 60 degrees, nor much greater than 120; and 
none of the Tides lefs than 200 yards, nor more than 350. 
This polygon, which is to be the interior one, fiiould 
have its Tides not lefs diftant from the houfes than fifty 
yards ; and the fortification is to be made from the inte¬ 
rior fide. Through every angle of the polygon draw a- 
line bifedting it; and on thefe lines, continued without 
the polygon, lay from the angular points the capitals of 
thofe polygons, as calculated in the preceding Table ; the 
angles of which are neareft to the angles in the given ir¬ 
regular polygon. Alfo on each fide of the capital, from 
the fqid angles, lay the demigorges, correfponding to the 
capitals ufed on the Tides of the polygon. Then the lines 
of defence being drawn, and the correfponding faces laid 
on them, the tuafter-line of the fortification to the given- 
irregular polygon may be readily completed ; to which 
the rampart, fofs, and proper out-works, may be annexed,, 
as before diredted. 
In circumfcribing the given place with a polygon pro¬ 
per to it, if it lhould happen that the (ides-, when drawn 
at the diftance of fifty yards from the houfes, make a po¬ 
lygon very different from that above diredfed ; then mull 
the politions and lengths of all thofe lines, or of fome of 
them, be changed, and various others tried, until the 
fituation will admit of one that will fnit the place, and 
come near tire fore-mentioned limits, which may be done 
by enclofmg a larger fpace, and permitting the fides of 
the polygon to extend farther from the houfes in fome 
places than fifty yards. And although by thefe means 
the fortification will be fomewhat more enlarged, and 
attended with greater labour and expence, yet, as by its 
nearer approach to regularity, it will be ftronger in itfelf,, 
and more effedtually anfwer the end propofed, every con- 
fideration lhould give way to the fecurity of the place. 
It is to be oblerved, that regularity is not confined 
ftridtly to fuch polygons only as can be circumfcribed by 
a circle, or nearly fo ; for a polygon inferibed in an oval 
figure- will have a great refemblance of regularity, and 
may be made almoft equally ftrong, by putting the 
ftronger out-works at the narrow ends. For as thefe ends, 
on account of their fmall breadth in proportion to the 
longer Tides, cannot flank the approaches of the enemy fo 
effedlually as the longer Tides, and as the enemy is not 
under a neceflity of extending his works fo much; confe¬ 
quently the fmaller ends may be more advantageoully at¬ 
tacked, and therefore lhould have their out-works made 
as far as can be impregnable. If the fituation is fuch, 
that one or more of the lides of the circumfcribing poly¬ 
gon cannot be made lefs than 400 yards or more ; then 
fuch lides lhould be divided into parts of fome number off 
s yards. 
