602 FORTI F I 
and here fome eminent engineers have thought it conve¬ 
nient to adapt the pofition of the ftreets to the climate in 
which the garrifon is fituated. Thus in hot countries 
they advife the Prreets to run north-eaft and fouth-weft; 
north-weft and Couth eaft ; for then the area of the ftreets 
w ill be fli ;ded by the buildings from the mid-day fun. In 
this manner New Brifac, part of Malta, and other regu¬ 
larly-built garrifon-towns, are laid out. But in cold cli¬ 
mates, they recommend all fortified towns to be planned 
for the ftreets to run north and Couth, eaft and weft, in 
order to enjoy as many hours fun as pofiibte. 
To plan the Jlreets and buildings .—About the middle, L, 
of the town, as projected in the engraving, deferibe a 
fquare, the fides of which fltall be parallel to the pofition 
of the intended ftreets; this fquare is called the great place 
of arms, and the fize of it fiiould be proportioned to that 
of the town, and to the number of troops defigned for its 
defence. Thus, in a fquare, make the fides of the place 
of arms about ninety yards ; in a pentagon, one hundred ; 
a hexagon, 120; a heptagon, 140; an oftagon, 160, &c. 
In the place of arms the troops parade, and are affembled 
for their daily exercife, and for general orders. 
In tire continuation of each fide of the fquare, draw 
ftreets about ten or twelve yards wide ; likewife through 
the middle of each fide draw a ftreet about twelve yards 
broad ; crofs thefe ftreets perpendicularly with others 
about eight yards wide ; make the parallel difiance of 
thefe crofs ftreets about forty yards, and continue all the 
lines to the rampart. It is not neceffary, that the middle 
ftreets going from the great place of arms L, fhould ter¬ 
minate directly againft the gate E, fig. 9. But it is forne- 
what more convenient, when the circumftances of the 
place will admit it to be fo. 
Make ftreets about twelve yards wide, parallel to the 
curtains, and bounded on one fide by the rampart. About 
fifteen yards diftant from this ftreet, within, draw another 
ftreet about nine yards wide. In the fpace H, between 
thefe two ftreets, the barracks for lodging the officers and 
foldiers are to be erefted; and in the ftreet next the ram¬ 
part the piles of (hot and bombs are to be placed^—The 
length of the plan of a barrack before a curtain is about 
380 yards, and the plan of a pavilion for the officers may 
be about twenty-five yards long by eighteen yards broad. 
Againft thofe curtains where the public gates, E, are 
placed, the barracks are difeontinued for about forty yards 
on each fide the gate, making an area of about eighty 
yards long, and thirty-fix broad, which ferves for a fmaller 
place of arms, where the guards and troops which are to 
defend the gateway draw up, in cafe of a furprife. The 
extremities of the barracks next the gates, marked I, in 
the engraving, and the baftions, are ufually affigned for the 
officers’ pavilions, being the ntoft airy and eligible places. 
Of the rectangular plats made by the interfeClions of 
the ftreets, thofe molt conveniently fituated are to be 
chofen for the public buildings; l’uch as the arfenal, 
church, town-houfe, market, lodge for the governor, and 
for the other chief officers. Befide the guard-houles at 
the gates, there fiiould be others made on the ramparts 
for the fentinels appointed for the night watch ; thefe 
guard-chambers are often placed at the centers of the 
necks of baftions, when in thofe places there are no cava¬ 
liers or magazines of powder. They are all'o well dif- 
pofed, when placed in the centers of the curtains where 
there are no public gates, efpecially when there is a water- 
gate, through which a canal or river conftantly furnifhes 
a large fupply of water. The arfenal lhould always be 
erected in a place the lead liable to accidents of fire ; and 
if there is a conveniency of water-carriage in the town, the 
arfenal lhould be placed as near as polfible to the naviga¬ 
tion or canal.—A citadel , or cajlle, where fuch an expence 
is advifable, and can be maintained, might be projected 
in one of the moft convenient angles of the town, and its 
communication defended or cut off from it by drawbridges, 
redoubts, ravelins, &c. for its greater fecurity whenever 
the town might be ftormed or taken by an enemy. 
CATION, 
Of fortified BRIDGES. 
The paffage acrofs the moats of fortified places is by 
bridges, moft commonly made of timber, and fupported 
by frames riling from the bottom of the ditch : fuch 
bridges are either private or public.—Private bridges ferve 
for the eafy communication between the town and the 
outworks. Public bridges are thofe by which carriages and 
paffengers go over when they come into or depart from 
the garrifon. Fortified bridges alfo con lift of two forts, name¬ 
ly, the fixed and moveable. The fixed or dormant bridges are 
thofe which are ftrongly joined to the fupporting piers ; 
and are never moved but in the cafes of repairs, or dur¬ 
ing a fiege. The moveable or draw-bridge is a floor of tim¬ 
ber framed together, one end of which ferves as an axis, 
by which the other end may be drawn up or let down at 
pleafure. The moft common method is by a kind of 
balance called plyers. The flyers confift of two ftrong 
levers, about twice the length of the bridge they are to 
lift, and are joined together by other timbers framed in the 
form of a St. Andrew’s crofs, which ferves as a counter- 
poife. The plyers are fupported by tw'o upright jambs, 
on which they fwing ; and the draw-bridge is raifed or let 
down by chains connected with the plyers and bridge. 
The breadth of a public bridge is ufually about fixteen 
feet, with rails and footway of about three feet on each 
fide ; but the breadth of the draw-bridge is only ten feet, 
and its length about fifteen. A draw-bridge is ufually 
placed clofe to the gate, whether it be the gate of the 
towm or that of an outwork ; and is then by means of the 
plyers drawn up againft the gate. But when a bridge is 
more than forty yards long, it is ufual, befide the draw¬ 
bridge at the entrance, to put another about the middle 
of the bridge. 
To projed a Bridge in the Plan cf a Fortrejs. —Before the 
gates draw four lines acrofs the moat or fofs, making 
three intervals or fpaces, the middle one being ten feet 
broad, and the fpace on each fide three feet. Divide the 
length of the bridge into parts of about fixteen feet long 
each, to exprefs the diftance between pier and pier, or the 
bays of building; and againft each divilion, on the out- 
fide of the lines, make a fquare of a foot, to exprefs the 
ends of the piers fupporting the bridge. Allow the bay 
next the gate for a draw-bridge ; and if the length of the 
bridge exceeds forty yards, allow the middle bay for ano¬ 
ther draw-bridge. Thefe are diftinguilhed by two diago¬ 
nals drawn acrofs the middle interval of thefe bays, that 
of the other bays having lines drawn acrofs them at a fmall 
diftance from one another, and the fpace on each fide left 
for the footway ; as at fig. 13 and 15 in the engraving. 
Of the ORILLON, and retired FLANK. 
When the befiegers of a fortrefs have effedted a breach, 
in the face of a baftion, they immediately attempt to take 
it by ftorm. In this attack, the fire from the flanks is al¬ 
ways the moft effedtual defence ; and cannon placed there, 
loaded with grape or cafe-(hot, will often perform won¬ 
derful execution. But of this the befiegers are well 
aware, and therefore endeavour to tiifmourd: all the can¬ 
non flanking their intended paffage of the fols ; and as 
this cannot always be prevented by the befieged, efpe¬ 
cially when the flanks are plain, the moft eminent engi¬ 
neers have propofed to build part of the flanks retired or 
behind the ordinary limits, leaving at the Ihoulder of the 
baftion a mafs of earth, commonly called an Oril/on, to 
ferve as a fkreen between the enemy’s diredL fire, and a 
part of the flank. In this covered part is referved one 
or two cannon, to be ufed only in defence of a breach 
made in the face of the next baftion. 
To confiruEl the Ori/lon and Retired Flank. —A t right angles 
to the face AS, fig. 10, draw from the angle of the fhoul- 
der the line S b equal to eight or nine yards, and make 6 
the centre of the arc S a, forming the onllon. From a 
point z, in the face of the next baftion, fig. 6, about fif¬ 
teen yards from the point A, draw through a, the line 
zm ; in which, and alfo in the line of defence Ar produced, 
* ‘ take 
