BOM 
other dimensions in 30ths of that diameter 
will be thus : 
Diameter of the bore or mortar... 30 
Diameter of the shell 29J 
Diameter of the hollow sphere 21 
Thickness of metal at the fuze hole 3| 
Thickness at the opposite pert 5 
Diameter of the fuze hole 4 
Weight of shell empty jf,d 
Weight of powder to fill it 
Where d denotes the cube of the diameter 
of the bore in inches. But shells have also 
lately been made with the metal all of the 
same thickness quite around. 
In general, the windage or difference be- 
tween thp diameter of the shell and mortar 
is jith of the .latter; also the diameter of the 
hollow part of the shell is ,1th of the same. 
Bombs are thrown out of mortars or 
howitzers; but they may also be thrown 
out of cannon ; and a very small sort are 
thrown by the hand, which are called 
granados. 
Bomb chest, a kind of chest filled usually 
with bombs, sometimes only with gunpow- 
der, placed under ground to tear and blow 
it up into the air with those who stand upon 
it. It was formerly set on fire by means 
of a saucisse fastened at oue end, but is 
new much disused. 
BOMB ketch, a small vessel built and 
strengthened with large beams for the use 
of mortars at sea. 
BOMBARD, a piece of ordnance an- 
ciently in use, exceedingly jhort and thick, 
and with a very large mouth. There have 
been bombards which have thrown a ball of 
300 pound weight. They made use of 
cranes to load them. 
BOMBARDIER, a person employed 
about a mortar. His business is to drive 
the fusee, fix the shell, load and fire the 
mortar, and to work with the fire-workers 
on ail sorts of fire-works, whether for war or 
recreation. 
BOMBARDMENT, is the act of assault- 
ing a city or fortress by throwing shells into 
it, in order to set it on fire, or otherwise 
demolish it. As one of the effects of the 
shell results from its weight, it is never dis- 
charged as a ball from a cannon, that is, by 
pointing it at a certain object : the mortars 
in England are fixed at an elevation of 45°. 
BOMBARDO, a musical instrument of 
the wind kind, much the same as the bas- 
soon, and used as a base to the hautboy. 
BOMBASINE, a name given to two 
BOM 
sorts of stuffs, the one of silk and the other, 
crossed, of cotton. 
BOMBAX, in botany, English silk cot- 
ton, a genus of the Monadelphia Polyandria. 
Natural order of Columniferte; Malvaceaj 
Jussieu. Essential character; calyx five- 
cleft ; stamina five or more ; capsule woody, 
five-celled, five-valved; seeds woolly; re- 
ceptacle five-cornered. There are four 
species, of which we shall notice the B, 
ceiba as being the most interesting : it grows 
to a great size in both Indies; it is one of 
the tallest trees in those countries ; the 
wood is very light and not much valued ex- 
cept for canoes; their trunks are so large 
as, w hen hollowed, to make very large ones. 
In Columbus’s first voyage it was related 
that a canoe was seen at the island of Cuba 
made of one of these trees, which was 
ninety-five palms long, of a proportional 
width, and capable of containing one hun- 
dred and fifty men. The canoes now made 
in the West Indies from this tree frequently 
carry from fifteen to twenty hogsheads of 
sugar, from six to twelve hundred weight 
each, the average about twenty-five tons 
burthen. When sawn into boards, and then 
well saturated with lime-water, the wood 
bears exposure to the weather many years ; 
it is also formed into laths for roofs, curing 
pots, and hogshead heading. When the tree 
decays it becomes a nest for the inacaca 
beetle, the caterpillar of which, gutted and 
fried, is esteemed by many persons one of 
the greatest delicacies. 
BOMBIC acid, in chemistry. The silk- 
worm forms an acid liquor which was sup- 
posed to be an acid of a peculiar nature, 
and accordingly received, in the new no- 
menclature, the name of bombic acid; but 
Mr. Murray thinks that this and some other 
acids formed by insects, as that by the ant, 
which is named formic acid, are acetic acid 
slightly disguised. 
BOMBYLIUS, in natural history, a ge- 
nus of insects of the order Diptera : the 
generic character is, mouth furnished with a 
very long porrected, setaceous, bivalve 
trunk, witli horizontal valves, including 
setaceous piercers. The insects of this 
genus have somewhat the appearance of 
the smaller kirids of humble-bees; thickly 
covered with erect downy hair; they fly 
with naucb rapidity, and may sometimes be 
observed to hang, as if suspended, over a 
flower, in the manner of some of the 
spinges, rapidly vibrating their wings and 
darting oft on the least disturbance to a 
considerable distance. There are forty- 
