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 a general symbolic method of logical inference. Given any propositions involving any number of terms, Boole showed how, by the purely symbolic treatment of the premises, to draw any conclusion logically contained in those premises. The second part of the Laws of Thought contained a corresponding attempt to discover a general method in probabilities, which should enable us from the given probabilities of any system of events to determine the consequent probability of any other event logically connected with the given events.

Though Boole published little except his mathematical and logical works, his acquaintance with general literature was wide and deep. Dante was his favourite poet, and he preferred the Paradiso to the Inferno. The metaphysics of Aristotle, the ethics of Spinoza, the philosophical works of Cicero, and many kindred works, were also frequent subjects of study. His reflections upon scientific, philosophical and religious questions are contained in four addresses upon The Genius of Sir Isaac Newton, The Right Use of Leisure, The Claims of Science and The Social Aspect of Intellectual Culture, which he delivered and printed at different times.

The personal character of Boole inspired all his friends with the deepest esteem. He was marked by the modesty of true genius, and his life was given to the single-minded pursuit of truth. Though he received a medal from the Royal Society for his memoir of 1844, and the honorary degree of LL.D. from the university of Dublin, he neither sought nor received the ordinary rewards to which his discoveries would entitle him. On the 8th of December 1864, in the full vigour of his intellectual powers, he died of an attack of fever, ending in suffusion on the lungs.

 BOOM, a word of Teutonic origin (cf. the Ger. Baum, tree, and the Eng. beam) for a pole, bar or barrier, used especially as a nautical term, for a long spar, used to extend a sail at the foot (main-boom, jib-boom, &c.). The “boom” of a cannon (note of a bell, cry of the bittern) is distinct from this, being onomatopoeic. In the sense of a barrier, a boom is generally formed of timber lashed together, or of chains, built across the mouth of a river or harbour as a means of defence. Possibly from the metaphor of a breaking boom, and the accompanying rush and roar, or from the rush of rising waters (mingled with the onomatopoeic use), “boom” began in America to be used of a sudden “spurt” or access of industrial activity, as in the phrase “a boom in cotton.” Hence the verb “to boom,” meaning to advertise or push into public favour.

 BOOMERANG, a missile weapon of the Australian aborigines and other peoples. The word is taken from the native name used by a single tribe in New South Wales, and was mentioned in 1827 by Captain King as “the Port Jackson term” (Nav. Surv. Coasts Austral. i. 355). It has been erroneously connected with the womera or spear-thrower, and equally erroneously regarded as onomatopoeic—for it does not “boom” but whistles in the air. Two main types may be distinguished: (a) the return boomerang; (b) the non-return or war boomerang. Both types are found in most parts of Australia; the return form was, according to General Pitt-Rivers, used in ancient Egypt; and a weapon which has a close resemblance to the boomerang survives to the present day in North-East Africa, whence it has spread in allied forms made of metal (throwing knives). Among the Dravidians of South India is found a boomerang-shaped instrument which can be made to return. It is, however, still uncertain whether the so-called boomerangs of Egypt and India have any real resemblance to the Australian return boomerang. The Hopis (Moquis) of Arizona use a non-return form. The general form of both weapons is the same. They are sickle-shaped, and made of wood (in India of ivory or steel), so modelled that the thickness is about th of the breadth, which again is th of the length, the last varying from 6 in. to 3 or 4 ft. The return boomerang, which may have two straight arms at an angle of from 70° to 120°, but in Australia is always curved at an angle of 90° or more, is usually 2 to 3 ft. in length and weighs some 8 oz.; the arms have a skew, being twisted 2° or 3° from the plane running through the centre of the weapon, so that B and D (fig. 1) are above it, A and E below it; the ends AB and DE are also to some extent raised above the plane of the weapon at C; the cross section is asymmetrical, the upper side in the figure being convex, the lower flat or nearly so; this must be thrown with the right hand. The non-return boomerang has a skew in the opposite direction but is otherwise similar.

The peculiarity of the boomerang’s flight depends mainly on its skew. The return boomerang is held vertically, the concave side forward, and thrown in a plane parallel to the surface of the ground, as much rotation as possible being imparted to it. It travels straight for 30 yds. or more, with nearly vertical rotation; then it inclines to the left, lying over on the flat side and rising in the air; after describing a circle of 50 or more yards in diameter it returns to the thrower. Some observers state that it returns after striking the object; it is certainly possible to strike the ground without affecting the return. Throws of 100 yds. or more, before the leftward curve begins, can be accomplished by Australian natives, the weapon rising as much as 150 ft. in the air and circling five times before returning. The non-return type may also be made to return in a nearly straight line by throwing it at an angle of 45°, but normally it is thrown like the return type, and will then travel an immense distance. No accurate measurements of Australian throws are available, but an English throw of 180 yds. has been recorded, compared with the same thrower’s 70 yds. with the cricket ball.

The war boomerang in an expert’s hand is a deadly weapon, and the lighter hunting boomerang is also effective. The return boomerang is chiefly used as a plaything or for killing birds, and is often as dangerous to the thrower as to the object at which it is aimed.

 BOONE, DANIEL (1734–1820), American pioneer and backwoodsman, of English descent, was born near the present city of Reading, Pennsylvania, on the 2nd of November (N.S.) 1734. About 1751 his father, Squire Boone, with his family settled in the Yadkin Valley in what is now Davie county, North Carolina, then on the frontier. Daniel worked on his father’s farm, and spent much of his time hunting and trapping. In 1755 he served as a wagoner and blacksmith in Braddock’s disastrous expedition against the Indians. In 1765 he visited Florida, and in 1767 he first visited the Kentucky region. With several companions, including John Finley, who had been there as early as 1752, he spent two years, 1769–1771, roaming about what is now Kentucky, meeting with numberless adventures, coming in conflict with roving bands of Indians, and collecting bear, beaver and deer skins. He served in Lord Dunmore’s War (1774), and in 1775 led to Kentucky the party of settlers who founded Boonesborough, long an important settlement. On the 7th of February 1778 he,