national Association of the Congo.

See H.M. Stanley, _The Congo and the Founding of its Free State_
(London, 1885).

BOMB, a term formerly used for an explosive shell (see AMMUNITION) fired
by artillery. The word is derived from the Gr. [Greek: bombos], a
hammering, buzzing noise, cf. "bombard" (q.v.). At the present day it is
most frequently used of a shattering or incendiary grenade, or of an
explosive vessel actuated by clockwork or trip mechanism, employed to
destroy life or property. In naval warfare, before the introduction of
the shell gun, explosive projectiles were carried principally by special
vessels known as bomb-vessels, bombards or, colloquially, bombs.

In geology, the name "bomb" is given to certain masses of lava which
have been hurled forth from a volcanic vent by explosive action. In
shape they are spheroidal, ellipsoidal or discoidal; in structure they
may be solid, hollow or more or less cavernous; whilst in size they vary
from that of a walnut to masses weighing several tons. It is generally
held that the form is partly due to rotation of the mass during its
aerial flight, and in some cases the bomb becomes twisted by a gyratory
movement. According, however, to Dr H.J. Johnston-Lavis, many of the
so-called bombs of Vesuvius are not projectiles, but merely globular
masses formed in a stream of lava; and in like manner Professor J.D.
Dana showed that what were regarded as bombs in Hawaii are in many cases
merely lava-balls that have not been hurled through the air. Certain
masses of pumice ejected from Vulcano have been called by Johnston-Lavis
"bread-crust bombs," since they present a coating of obsidian which has
been bent and cracked in a way suggestive of the crust of a roll. It is
probable that here the acid magma was expelled in a very viscous
condition, and the crust which formed on cooling was burst by the steam
from the occluded water. Some of the bombs thrown out during recent
eruptions of Etna consist of white granular quartz, encased in a black
scoriaceous crust, the quartz representing an altered sandstone. The
bombs of granular olivine, found in some of the tuffs in the Eifel, are
represented in most geological collections (see VOLCANO).

BOMBARD (derived through Med. Lat. and Fr. forms from Gr. [Greek:
bombein], to make a humming noise), a term applied in the middle ages to
a sort of cannon, used chiefly in sieges, and throwing heavy stone
balls; hence the later us