FORTIF 
fake the brifures or breaks am and rn, each ten yards. 
From m and n, fig. io, with the radius mn, defcribe arcs 
cutting in d, which make the centre of the arc mn, or 
concave flank. In dm produced, which ferves as the ter¬ 
mination at this end, lay the feveral breadths of the parts 
of the rampart ; as the parapet — 6 yards, foot-bank — 2 
yards, walk 12 yards, and the flope = 4 yards ; then 
front the centre d, through thofe points, defc.-ibe arcs, 
meeting the parapet, foot-bank, and rampart lines of the 
brifure, thefe being in the continuation of the like lines 
drawn within the face of the next baftion. The parapet 
of the orillon is drawn parallel to Srz, at fix yards dif- 
tance. The axis or middle line of each uncovered ern- 
brafure in the flank tends toward a point about the mid¬ 
dle of the fofs oppofite the flanked angle of the next baf¬ 
tion. The wall in the upper brifure am, as it cannot be 
battered, need not be above two or three feet thick to fup- 
port the earth behind it. Through this wall is projected 
a fally-port, coming out at the bottom of the fofs if a dry 
one, or a little above the water-line in a wet one. The de- 
fcent to this port is by a paflage under the rampart of the 
flank ; but in ftraight flanks the (ally-port is in the cur¬ 
tain next the angle of the flank, the paflage to it being 
under the rampart of the curtain.—The entrance into the 
fally-ports is marked on the inner flope of the rampart 
againft the letters v. 
Of Casemated or Double Flanks. —The progrefs 
of a belieging army generally depends on their having a 
much greater number of troops than is contained in the 
town befieged, and of forming a greater fire on the town 
than it can return ; it has therefore been the care of en¬ 
gineers to prevent as much as poflible the progrefs of the 
befiegers’ batteries, by furnifhing the town with an equal, 
or rather a fuperior fire ; and this has been propofed to 
be effected by eredting fecond and third flanks, one be¬ 
hind another, gradually more elevated than the firft. For 
as it is the primary objedl of a befieging army to filence 
the fire of the flanks, before they avail themfelves of the 
breach made in the baftion, they are obliged, for that pur- 
pofe, to eredt batteries againft the flanks, and keep them 
playing at the fame time with thofe againft the faces. 
Now thefe batteries for the ruin of the flanks can only 
be made w’ithin ten or twelve yards of the head of the 
glacis, and their length not greater than about forty yards, 
containing at mod fix or feven cannon. Therefore if the 
befieged can by any means preferve the cannon in the oppo¬ 
fite flank, and have a greater number there than in the 
battery oppofed, their fire will of courfe be fuperior, and 
foon filence the battery intended to offend them ; this is 
the end expedted to be accomplifhed by double or cafe . 
matedflanks. 
In fome places two or three tier of cannon are placed 
one above the other, the upper ones being fupported by 
a vaulted work, as in the Tower of London ; but fuch a 
conftrudtion being found very inconvenient, on account 
of the fmother produced in the vaults, they are now ge¬ 
nerally conftrudled open. Yet the cafemated flanks have 
been condemned by fome writers, becaufe they may be 
rendered ufelefs by the enemy’s bombs: but were this 
objection well founded, it would hold equally againft any 
fmall work ; and it would thence follow, that it were beft 
not to have any places of defence at all.—Suffice it to 
fay, that the utility of fuch works has been commended 
by the moft eminent engineers. 
Works for the defence of the fofs, or moat, are tenails, 
or ramfliorns, or caponiers. The tenail is a work raifed in 
the ditch before the curtain upon the lines of defence. 
The ramjhorn is a curved tenail, railed in the fofs before 
the flanks, and prefenting its convexity to the covered 
way. The caponier is a kind of covered-way or gallery 
acrofs a dry moat before the middle of the curtain ; and 
limited between the lines of defence and the counterfcarp. 
The tenails (hould never rife above the common ground 
level, but rather be two or three feet lower : they confift 
of a rampart twelve or fifteen yards thick, covered by a 
a 
CATION. 60.1 
parapet cannon-proof, with cm? or two foot-banks.. Thefe 
works mu ft be placed at fuch a diftance from the curtains 
and flanks, that the fplinters of done knocked off by the 
befiegers’ cannon, may not annoy the troops ported there 
to flank the enemy in their attempt to carry the paflage of 
the fofs. The caponier is of fimilar life, ufually funk two 
or three feet lower than the bottom of the fofs. It is 
about three yards broad, covered by a parapet fix feet 
high on each fide, which (lopes like a glacis about fifteen 
yards broad. It is frequently covered by a roof made 
with hurdles, to fuftain a floor of earth about a foot 
thick, and the whole fupported with planks that are 
mulket-proof, with loop-holes for the befieged to fire 
through. 
To con/lruEl Tenails with Flanks. —Parallel to the curtains 
and flanks, draw the lines eg, fig. n, at four or five yards 
diftance, and Ee, G g, at ten yards diftance : from F, and 
D, the centers of CG, CF, draw the flanks Ffl, D d, at 
right angles to the lines of defence, A g, Be; draw the 
curtain dfl and put in the rampart, parapet, and foot-bank. 
For tenails with faces only, take the diftances from the 
curtain and flanks, the fame as before ; and to the lines 
of defence annex the rampart and parapet, as (hewn at 
fig. 12.—For tenails with faces and curtain, proceed thus: 
when the lines of defence crofs one another in D, fig. 3^ 
fo near the curtain that there is not room for the thicknefs 
of the rampart and its diftance from the curtain, project 
the face ab, cd, each of $ of aD, and the curtain db. 
To conflruFl the Caponier. —From the exterior flanking 
angle D, fig. 12, draw a line Dp, to the angle of the coun¬ 
terfcarp p ; on each fide of Dp draw parallel lines, at the 
diftances of one and a half, two and a half, and fifteen 
yards from Dp; thefe lines, limited by the lines of de¬ 
fence and counterfcarp, form the caponier. This work, 
which is ufed only in a dry fofs, ferves, befides its defence 
of the fofs, for a convenient communication between the 
town and its outworks; and in this cafe there is ufually 
a circular excavation made in the angle of the counter¬ 
fcarp, from which the troops may defile without being 
feen by the enemy. 
To conflruEl a Ramfliorn. —A line Da, fig. 13, drawn from < 
D, the angle of the (boulder, at right angles to the line of 
defence, its interfeftion a with BI, the other line of de¬ 
fence continued, gives the centers; from which, with 
the radius aD, defcribe the outline AC of the ramfliorn, 
CD being equal to ten yards ; and annex a parapet, foot- 
bank, and walk, as in the other tenails. 
Of OUTWORKS. 
Outworks confift of thofe parts of a fortification which 
are advanced beyond the fofs, ferving to augment the 
defence of the town, to cover the gates, bridges, and 
other vulnerable parts ; toenclofe thofe eminences which 
command the town ; to furround and defend the fuburbs, 
if any; and, in (hort, to throw fo many obftacles in the 
way of the befiegers, that, by the length of the fiege, the 
enemy may wafte both his time and troops: fuch pro- 
tradtion alfo frequently affords an opportunity of obliging 
the enemy to raife the fiege, either by the approach of a 
relieving army, or by the fetting-in of a feafon unfit for 
military operations. Thefe outworks are various, fuch 
as ravelins, half-moons , lunettes, countergards , horn-works t 
crown-works, tenails, &c. 
The conftrudtion of outworks depends on the fame 
principles as thofe of the place itfelf; to which the fol¬ 
lowing rules may be added :—1. Every part of an out¬ 
work ought to be flanked or defended either from fome 
neighbouring work, or from the town itfelf; that the 
enemy may not find any place of real (helter among the 
outworks, without being at the labour of throwing up 
lines for himfelf. 2. Every outwork ought to be com¬ 
manded from the town ; and therefore the more advanced 
works are ever to be the loweft. The gradation ufually 
obferved from work to work is about three feet 5. that is, 
the ramparts of all works advanced before a place gra¬ 
dually 
