FORTIFICATION. 
derably lower than that of A, which com- 
mand it, both by the cannon it mounts, 
and by its musqnetry ; the parapet being 
sloped so as to give a direct fire into it, 
when the firelocks are laid upon the slope 
at x. In this counterguard the interior of 
the parapet is not reveted; therefore the 
banquette I is ascended from the terre- 
pleine, H, by a slope of gazon. The para- 
pet C, &c. are nearly of the same dimen- 
sions as F on the rampart A, except that 
the rampart B is much lower than A. The 
exterior of B has a cordon, level with the 
terre-pleine H, but its parapet is faced 
with turf, which the cordon assists to sup- 
port. If the counterguard B w'ere not de- 
fended by other out-works in its front, it 
would have a glacis come close to it, leaving 
only a very small passage between its ex- 
terior and the palisades ; here we suppose 
it to have a small dry ditch D, reveted 
both in the scarp and counterscarp, but 
without a berm, which is very rarely, if 
ever, allowed to an outwork. 
The third figure affords a more general 
profile of the works, and gives some 
idea of the usual defilement of the outworks, 
B and C, from the body of the place A. 
D is the foot of the glacis, where it meets 
the terre-pleine, or level of the country, 
which we always suppose to be esplanaded, 
(that is, laid flat) and not affording any co- 
ver to the enemy for at least 1000 yards 
from the outworks. The glacis is usually 
made full 50 yards long, and of such an 
ascent as to give, on an average, about 
eight feet height at its crest. Supposing the 
angle of the raveline to be 25 yards within 
the crest of the glacis, the continuation of 
the ascent would strike the cordon of the 
rampart, C, at 12 feet from the level of the 
terre-pleine ; this determines the height at 
which a cannon, standirig on the terrg-pleine 
of the raveline, C, would graze the glacis, 
while the slope of the embrasures would 
allow the guns to play into the covert way. 
It is to be observed, that, according to this 
construction, all the scarp, below the cor- 
don, is completely hid from the enemy, and 
cannot be battered so long as the crest of 
the glacis remains at its proper height. 
Hence partly arises the great difficulty of 
breaching the saliant angles of outworks. 
Now let us estimate the redoubt, B, at 
25 yards within the Hanked angle of the 
bastion, C. It is to be remarked, that this 
defence is made with the view to render 
the raveline untenable to an enemy ; and 
that, for the preservation of its parapet, 
the rampart, of the redoubt, B, should be a 
mere trifle above the level of that of the 
raveline, C. The faces of the contiguous 
bastions of the same front, enfilade the faces 
of the raveline ; but it is also requisite, that 
the fire from the curtain should, on emer- 
gency, (for the bastions may be silenced) 
contribute to drive the assailants from that 
part of the raveline which lays beyond the 
redoubt, at all events to clear its ramparts. 
Therefore, we will state the terre pleine of 
B, at only one foot above that of C. This 
pats the redoubt completely out of the 
line of defilement, and, in fact, generates 
another, by allowing the curtain, A, to 
throw shot into C, without touching any 
part of B, as may be seen by following the 
line from the’cordon of A to the terre-pleine 
of C. Hence B cannot be battered from 
the glacis. 
But wiiere it is necessary to produce the 
greatest accumulation of strength against 
any exterior point, it is often found proper 
to raise every part of the interior defences, 
so that they should all overlook like a flight 
of steps, as shewn in fig. 4, where the cita- 
del is supposed to stand on a conical hill, 
high above the town, (which is only defend- 
ed by a glacis and covert way, surrounding 
a ditch and rampart) and lias four rows of 
cannon, at different heights, each command- 
ing the exterior defences, and the surround- 
ing country, as far as the shot can reach. 
This, though not a common figure, nor a 
common mode of fortifying such places, (for 
works are rarely carried like hoops or bands 
around hills) will fully illustrate the gene- 
ral tendency of the foregoing details, and 
to the ordinary reader, who cannot here ex- 
pect to find all the minute items and varie- 
ties abounding in this very intricate science, 
will give a tolerable insight into the princi- 
ples on which fortifications are usually con- 
structed, , 
To return to fig. 3. It will be seen that 
the elevation of A would, on the calculation 
there assumed, be such as to carry the cor- 
don of its terre-pleine so high, that its re- 
vetement could be battered from the gla- 
cis, D O, without touching C or B. To 
remedy this, where such an exposure would 
be injurious, (for it is in some instances 
expedient, as above described, to direct all 
the force exteriorly, especially where the 
outwork lays upon a navigable river, and 
that ships can be brought to bear upon the 
works,) the redoubt must be lowered to the 
same level of terre-pleine as the raveline ; 
and, indeed, it may even, in some few in- 
