Pirate 
CCcLVHL 
rig. & 
To deter- 
Taine the 
relhef or 
uncren 
ground. 
to be considered as separate 
om le constructed by the rules laid down for that of 
oan. The profile of a place is represented in 
considerable i 
different works. The method now 
is as follows: 
A horizontal plane is su to pass through the 
i int of the d within the distance of 2400 
feet of intended enceinte. From this plane, which 
is called the plane of comparison, vertical lines are 
drawn to every remarkable point of the place to be 
fortified, forming as it were a chart of soundings, in 
which the of comparison represents the surface 
of the sea. verti lines, as in the case of sound- 
ings, are called coftes, their different lengths being 
marked on the plane. If these lengths differ no more 
than from two to three feet, the ground may be consi- 
dered as level, and fortified accordingly. If the ine- 
walities are greater than this, re must be had to 
them in determining the relief. 
From what has been already said, it may easily be 
ived, that the crests of all the parapets, on the 
same front of a fortification, terminate in a plane more 
or less inclined to the horizon, as the different works 
are more or less elevated above one another. In the 
same manner, the surfaces of all the terre-pleins, and 
indeed of any other corresponding parts of the works, 
lie in a plain parallel to the former, and as far distant 
from it as these are lower than the Bs ope Such 
planes, in general, are called planes of 
that which passes through the covered way, the pia 
of view or of site, because it determines all the others. 
The plane of view ought to have such a position, that 
it will pass from four to six feet above the highest point 
within 2400 feet of the front. As three points are ne- 
cessary in determining any plane, the three employed 
in this case are two in the line intended for the covered 
way, and one on the summit, or rather five to six feet 
above the summit of the highest ground about the 
place. If the line joining the two first points be hori- 
zontal, the cottes of the plane of view, or the distances 
of the different points in the plane of view from the 
plane of observation, may be found by the rules al- 
ready given for determi the relief of a fortification 
or leve d. If that line is not horizontal, the 
angle of its inclination is first to be ascertained, and 
from that the cottes may be easily computed. 
If an eminence running along a front be nearly of 
an or height, the front ought to be parallel to it ; 
but if the eminence is higher at one extremity, the 
front ought to be at a greater distance from the higher 
part than from the lower. 
If a front runs across an eminence, the of the 
front at the bottom on each side are to be covered b 
saliant works on the top of the eminence, and the whole 
front may then be constructed on one plane of view. 
If it crosses two eminences with a valley between, it 
will require two planes of view, always taking care that 
there be saliant works on the eminences, by which the 
enemy may be obliged to open his trenches at a greater 
distance. If the place be surrounded by eminences on 
all sides, each front will require a plane of view for itself. 
efilement; and ly 
convex towards the enemy, 
iat Oe doe be level and i 
one another. e cou ; 
be n ts-have sire ‘of lees thaws Ne 
Hl 
g, 
‘ 
eeH? 
to é 
junction of the river with other rivers—on 
eminences, or any other advantageous position. 
should also be taken to cover the sluices that 
constructed for inundating the country, when 
measure is rendered Fortifications should 
s 
E 
ie 
the frontier. But the side which chiefly demands the 
attention of the engineer, is the sea coast, which is al- 
ways more cme penetrated, and consequently requires 
the assistance of every advantageous position that can 
possibly be obtained. — sidan | 
The enceinte of a fortification may be a figure of’. 
number of sides, from a ards, the 
of the side in each being 
illy 
importance to determine 
the comparative merits of each. hoy ’ 
The square may be readily fortified, so as, by means The square, 
of ravelins, i and tenailles, to be equal- 
y strong on every side. But the garrison whi i 
capable of containing is com ively small ; 
scarcely possible to make it hold out a 
twelve to fifteen days. The same remarks are applica- 
ble to the pentagon, neither the one nor the other 
being fitted tor an important position. ae 
The hexagon is superior to either of the former. Its Hexagon. 
faces and flanks are sufficiently large ; it will admit of 
other outworks besides ae Ac, coun’ ds, 
tenailles, and will contain 2400 infantry and 100 ca- 
valry. It can only be used, however, in situations 
where assistance can be quickly obtained, as it cannot 
4 mae to hold out longer than from twenty-two to 
ys. 
_ The heptagon and octagon i adore. sive: Of Heptagom 
from 3000 to 3500 men ; and, by the help of outworks and octa- 
and mines, 
resistance. defence te lhe: : my extend 
from twenty-two to thirty-five ) an t of the 
“ from thirty ¥ to pial - 
e enneagon, decagon, and en , are Capable Enneagony, 
of containing 4000 or 5000 men; an equently, &c. 
from so large a garrison, can spare a greater tines 
the defence of outworks, than a polygon of fewer sides. 
If, with the outworks, they the advan of 
inundation, they may be considered as places of the 
first order. Under these circumstances, they may hold 
out from forty to sixty days. ~ 
Dodecagons and polygons of more than twelve sides 
are considered as the stro of all fortifications. They gon, &¢. 
contain a garrison sufficient to defend not only the places © 
themselves, but also the i them, as. 
well as smaller forts in If all the 
gon. 
passages leading to 
the neighbourhood. 
hat cing capable of a considerable 8™ = 
e 
The penta- | 
! 
‘* 
