Bonnet, in fortification, a transverse elevation of the parapet, or 
traverse and parapet, used either to prevent the enemy from 
seeing the interior of a work from some elevated point, or, in 
barbette batteries, to protect men and guns from flanking fire. In 
these latter batteries, the guns firing over the crest of the parapet 
have to be placed on high traversing platforms, on which the 
gun-carriage rests, recoils, and is run forward. The men are, 
therefore, partly exposed to the fire of the enemy while they serve 
the gun; and flanking or ricocheting fire is especially dangerous, 
the object to be hit being nearly twice as high as in batteries with 
embrasures and low gun-carriages. To prevent this, traverses or 
cross parapets are placed between the guns, and have to be 
constructed so much higher than the parapet, that they fully cover 
the gunners while mounted on the platform. This superstructure 
is continued from the traverse across the whole thickness of the 
parapet. It confines the sweep of the guns to an angle of from 90° 
to 120°, if a gun has a bonnet on either side. 

Bonnet-a-Prétre, or Queue d’Hirondelle (swallow tail), in field 
fortification, is an intrenchment having 2 salient angles, and a 
reentering angle between them. The latter is always 90°, the 2 
salient angles mostly 60°, so that the 2 outer faces, which are 
longer than the inner ones, diverge to the rear. This work is 
sometimes used for small bridge heads, or in other situations 
where the entrance to a defile has to be defended. 

Written between September 16 and 29, Reproduced from The New Ameri- 
1857 can Cyclopaedia 

Cyclopaedia, Vol. III, 1858