766 
extensive flanks and demigorges are superior 
to narrow and confined ones. The more ca- 
pacious the flank is, the better calculated will 
it prove tor the disposition of a formidable 
train ot artillery. From this conviction many 
writers, in their proposed systems of fortifi- 
cation, have added a second flank, in order to 
augment the line of defence ; but they did 
not foresee that this second flank is not only 
i neap able of covering the face of the op- 
posed bastion, except in a very oblique and 
insecure direction, but that the right flank, or 
the flank of the bastion, is thereby more ex- 
posed to the enemy’s batteries, which, it 
must be acknowledged on all sides, is a great 
fault. 
The prevailing system of the present day 
is, to make the flanks of the bastion as wide 
as possible, without having recourse to a se- 
cond flank, unless it be absolutely necessary. 
Those gorges are likewise best which are 
most capacious, because they afford space 
and ground in the bastion for the construc- 
tion of entrenchments within, should the ene- 
my have effected a practicable breach. 
All parts of a fortification which stand ex- 
posed to the immediate attacks of a besie- 
ging enemy, must be strong enough to bear 
the boldest attempts, and the most vigorous 
impressions. I his is a self-evident maxim, 
•because it must be manifest to the most com- 
mon understanding, that works are erected 
round a place for the specific purpose of pre- 
venting an enemy from getting possession of 
it. It consequently follows, that flanked an- 
gles are extremely* defective when they are 
too acute, since their points may be easily 
flanked and destroyed by the besiegers’ can- 
non. 
The Dutch construct at sixty degrees ; but 
according to Vauban’s method, To work 
should be under seventy -five degrees, unless 
circumstances and situation should particu- 
larly require it. 
The diagram annexed, together with the 
explanation that follows, will convey an idea 
of M. Vauban’s method, in respect to the 
fortification of towns. See Plate Farriery, &c. 
Inscribe in a circle a polygon of as many 
sides as the fortification is designed to have 
fronts; let AB, fig. 9, be one of the sides 
ot halt an hexagon, which bisect by the 
perpendicular CD ; divide half of it AC 
into nine equal parts, and one of these into 
ten others; then these divisions will serve as 
a scale to construct all the parts of the forti- 
fication, and each of them is supposed to be 
a toise or fathom, that is, six French feet ; 
and therefore the whole side AB is supposed 
to be 180 toises. As the dividing a line into 
so many equal parts is troublesome and te- 
dious, it is more convenient to have a scale 
of equal parts, by which the works may be 
constructed. 
If therefore, in this case, the radius is 
taken equal to 1 80 toises, and the circle de- 
scribed with that radius being divided into 
six equal parts, or the radius being carried 
six times round, you will hive an hexagon in- 
scribed ; AB being bisected by the perpendi- 
cular CD as before, set off 30 toises from C 
to D, and draw the indefinite lines ADG, 
BDF ; in which take the parts AE, BH, 
each equal to 50 toises ; from the centre E 
describe an arc through the point H, meet- 
ing AD in G, and from the centre H describe 
an arc through the point E, meeting I3D in 
FORTIFICATION. 
F ; or, which is the same, make each of the* 
lines EG, HF, equal to the distance EH; 
then the lines joining the points A, E, F, G, 
H, B, will be the principal or outline of the 
front. 
If the same construction be performed on 
the other sides of the polygon, you will have 
the principal or outline of the 'whole fortifi- 
cation. If, with a radius of 20 toises, there 
be described circular arcs from the angular 
points B, A, M, T, and lines are drawn from 
the opposite angles E, II, &c. so as to touch 
these arcs, their parts ab, be, kc. together 
with these arcs, will present the outline of the 
ditch. 
Definitions. 
1. The part FEALN is called the. bastion. 
2. AE, AL, the faces of the bastion. 
3. EF, LN, the flanks. 
4. FG, the curtin. 
5. FN, the gorge of the bastion. 
6. AG, BF, the lines of defence. 
7. AB, the exterior side of the polygon. 
8. CD, the perpendicular. 
9. Any line which divides a work into two 
equal parts is called the capital of that work. 
10. a, b, c, the counterscarp of the ditch. 
1 1 . A, M, the flanked angles. 
12. H, E, L, the angles of the shoulder, or 
shoulder only. 
13. G, F, N, the angles of the flank. 
14. Any angle whose point turns from the 
place is called saliant angle, such as A, M : 
and any angle whose point turns towards the 
place, re-entering angle, such as b, F, N. 
15. If there be drawn two lines parallel to 
the principal or outline, the one at 3 toises 
distance, and the other at 8 from it, then the 
space yx included between the principal one 
and that farthest distant is called the ram- 
part. 
And the space r, contained by the prin- 
cipal line and that near to it, and which is 
generally stained black, is called the parapet. 
16. There is a fine line drawn within four 
feet of the parapet, which expresses a step 
called banquette. 
All works have a parapet of three toises 
thick, and a rampart of from 8 to 10, besides 
their slopes. The rampart is elevated more or 
less above the level of the place, from 10 to 
20 feet, according to the nature of the 
ground, and the particular constructions of 
engineers. 
'1 he parapet is a part of the rampart ele- 
vated from 6 to /■§ feet above the rest, in or- 
der to cover the troops which are drawn up 
there from the fire of the enemy in a siege ; 
and the banquette is two or three feet higher 
than the rampart, or about four feet lower 
than the parapet ; so that when the troops 
stand upon it, they may just be able to fire 
over the parapet. 
17. The body of the place is all that which 
is contained within this first rampart ; for 
which reason it is often said to construct the 
body of the place : which means, properly, 
the construction of the bastions and curtins. 
18. All the works which are constructed 
beyond the ditch, before the body of the 
place, are called outworks. 
II. Of IRREGULAR FORTIFICATION. 
The most essential principle in fortifica- 
tion consists in making all the fronts equally 
strong, so that the enemy may find no parti- 
cular advantage in attacking either of the 
sides. But this can only occur in a regular 
work, situated in a plain, or even ground ; 
consequently there are but few places which 
are not irregular : and tire great art here is, 
to remedy the defects and inconveniences 
occasioned by this circumstance. 
It the situation to be fortified is an old 
town, inclosed by a wall or rampart, the en- 
gineer ought to consider well all the different 
circumstances of the figure, position, and na- 
ture ol the ground, and to regulate his plan 
accordingly, so as to avoid as many disad- 
vantages, on one hand, and to obtain as many 
advantages, on the other, as possible. If 
there is a rampart without towers, it must be 
decided whether bastions ought not to be 
added, and ravelins and counter-guards con- 
structed. Special care must be taken to 
make all the sides ot the polygon nearly 
equal, and that the length of the lines of-de- 
fence do not exceed the reach of musket- 
shot. V> herever the sides are inaccessible, 
either on account of a precipice, or marshy 
ground, they may be made much larger than 
those which are easy of access. 
If the place to be fortified is new, and the 
situation will not admit of a regular con- 
struction, particular care must be taken to 
choose such a spot of ground as is most ad- 
vantageous. All hills, or rising grounds, 
should be avoided, as these might command 
some parts of the works ; marshes, because 
such situations are unwholesome, and lakes 
and standing waters for the same reason, ex- 
cept they can be rendered navigable. 
Places built on mountains or rocks should 
never be large ; for their use is generally to 
guard passes or inlets into a country, and it 
is difficult to provide for a large garrison un- 
der such circumstances. When fortifications 
are to be placed in the neighbourhood of the 
sea, for the purposes of protecting trade, the 
first thing to be considered is their situation, 
which ought to afford a good harbour for 
shipping. \\ hen M. Vauban fortified near 
rivers, he always made the exterior side next 
to the water much longer than any of the 
others ; for as that part is not so liable to be 
attacked, great and manifest advantages were 
of course derived from this circumstance. 
To illustrate this method of M. Vauban’s, 
we shall give the plan of Hunninghen. That 
place was built for the sake of having a bridge 
over the Rhine, for which reason he made it 
only a pentagon ; the side AB (fig. 10) next to 
the river is 200 toises, and each of the others 
but 180. 
About the space abc, which lies before the 
front AB, is a stone wall ; and the passages, 
are shut up with sluices, to retain the wa- 
ter in the ditches in dry seasons ; and to pre- 
vent an enemy from destroying the sluice 
near the point c, whereby thewater would run 
out and leave the ditches dry, the redoubt y 
was built in the little island hard by, in order 
to cover that sluice ; without which precau- 
tion the place might be insulted from the 
river side, where the water is shallow in dry 
seasons. 
The hornwork K, beyond the Rhine, was 
built to cover the bridge ; but as this work 
cannot be well defended across the ri\ er, the 
hornwork H was made to support the other. 
Before finishing the description of this 
plan, we shall show how to find the long side 
