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 Gr. , a hammering, buzzing noise, cf. (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 ).

 BOMBARD (derived through Med. Lat. and Fr. forms from Gr. , 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 use as a verb (see ). The name, in various forms, was also given to a medieval musical instrument (“bombard,” “bumhart,” “pumhart,” “pommer”), the forerunner of the bass oboe or schalmey. At the present day a small primitive oboe called bombarde, with eight holes but no keys, is used among the Breton peasants.

 BOMBARDIER, originally an artilleryman in charge of a bombard; now a non-commissioned officer in the artillery of the British army, ranking below a corporal.

 BOMBARDMENT, an attack by artillery fire directed against fortifications, troops in position or towns and buildings. In its strict sense the term is only applied to the bombardment of defenceless or undefended objects, houses, public buildings, &c., the object of the assailant being to dishearten his opponent, and specially to force the civil population and authorities of a besieged place to persuade the military commandant to capitulate before the actual defences of the place have been reduced to impotence. It is, therefore, obvious that mere bombardment can only achieve its object when the amount of suffering inflicted upon non-combatants is sufficient to break down their resolution, and when the commandant permits himself to be influenced or coerced by the sufferers. A threat of bombardment will sometimes induce a place to surrender, but instances of its fulfilment being followed by success are rare; and, in general, with a determined commandant, bombardments fail of their object. Further, an intentionally terrific fire at a large target, unlike the slow, steady and minutely accurate “artillery attacks” directed upon the fortifications, requires the expenditure of large quantities of ammunition, and wears out the guns of the attack. Bombardments are, however, frequently resorted to in order to test the temper of the garrison and the civil population, a notable instance being that of Strassburg in 1870. The term is often loosely employed to describe artillery attacks upon forts or fortified positions in preparation for assaults by infantry.

 BOMBARDON, or, the name given to the bass and contrabass of the brass wind in military bands, called in the orchestra bass tuba.

The name of bombardon is unquestionably derived from bombardone, the Italian for contrabass pommer (bombard), which, before the invention of the fagotto, formed the bass of medieval orchestras; it is also used for a bass reed stop of 16 ft. tone on the organ. The bombardon was the very first bass wind instrument fitted with valves, and it was at first known as the corno basso, clavicor or bass horn (not to be confounded with the bass horn with keys, which on being perfected became the ophicleide). The name was attached more to the position of the wind instruments as bass than to the individual instrument. The original corno basso was a brass instrument of narrow bore with the pistons set horizontally. The valve-ophicleide in F of German make had a wider bore and three vertical pistons, but it was only a “half instrument,” measuring about 12 ft. A. Kalkbrenner, in his life of W. Wieprecht (1882), states that in the Jäger military bands of Prussia the corno basso (keyed bass horn) was introduced as bass in 1829, and the bombardon (or valve-ophicleide) in 1831; in the Guards these instruments were superseded in 1835 by the bass tuba invented by Wieprecht and J. G. Moritz.

The modern bombardon is made in two forms: the upright model, used in stationary band music; and the circular model, known as the helicon, worn round the body with the large bell resting on the left shoulder, after the style of the Roman cornu (see ), which is a more convenient way of carrying this heavy instrument when marching. The bombardon, and the euphonium, of which it is the bass, are the outcome of the application of valves to the bugle family whereby the saxhorns were also produced. The radical difference between the saxhorns and the tubas (including the bombardon) is that the latter have a sufficiently wide conical bore to allow of the production of fundamental sounds in a rich, full quality of immense power. This difference, first recognized in Germany and Austria, has given rise in those countries to the classification of the brass wind as “half” and “whole” instruments (Halbe and Ganze Instrumente). When the brass wind instruments with conical bore and cup-shaped mouthpiece first came into use, it was a well-understood principle that the tube of each instrument must theoretically be made twice as long as an organ pipe giving the same note; for example, the French horn sounding the 8 ft. C of an 8 ft. organ pipe, must have a tube 16 ft. long; C then becomes the second harmonic of the series for the 16 ft. tube, the first or fundamental being unobtainable. After the introduction of pistons, instrument-makers experimenting with the bugle, which has a conical bore of very wide diameter in proportion to the length, found that baritone and bass instruments constructed on the same principle gave out the fundamental full and clear. A new era in the construction of brass wind instruments was thus inaugurated, and now that the proportions of the bugle have been adopted, the tubes of the tubas are made just half the length of those of the older instruments, corresponding to the length of the organ pipe of the same pitch, so that a euphonium sounding 8 ft. C no longer needs to be 16 ft. long but only 8 ft. The older instruments, such as the saxhorns, with narrow bore, have therefore been denominated “half instruments,” because only half the length of the instrument is of practical utility, while the tubas with wide bore are styled “whole instruments.” Bombardons are made in E flat and F of the 16 ft. octave, corresponding to the orchestral bass tuba, double bass in strings, and pedal clarinet and contrafagotto in the wood wind. The bombardon in B flat or C, an octave lower than the euphonium, corresponds to the contrabass tuba in the orchestra.