markable, however, was that part of his
system, fully stated in his _Laws of Thought_, which formed 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.

An excellent sketch of his life and works, by the Rev. R. Harley,
F.R.S., is to be found in the _British Quarterly Review_ for July
1866, No. 87. (W. S. J.)

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
a