ectrostatic and magnetic experiments (see GRAVITATION and
ELECTROMETER). The term also connotes the idea of equality or equalization;
_e.g._ in the following expressions: "balance," in bookkeeping, the amount
which equalizes the debit and credit accounts; "balance wheel," [v.03
p.0235] in horology, a device for equalizing the relaxing of a watch or
clock spring (see CLOCK); the "balancing of engines," the art of minimizing
the total vibrations of engines when running, and consisting generally in
the introduction of masses which induce vibrations opposed to the
vibrations of the essential parts of the engine.

BALANCE OF POWER, a phrase in international law for such a "just
equilibrium" between the members of the family of nations as should prevent
any one of them from becoming sufficiently strong to enforce its will upon
the rest. The principle involved in this, as Hume pointed out in his _Essay
on the Balance of Power_, is as old as history, and was perfectly familiar
to the ancients both as political theorists and as practical statesmen. In
its essence it is no more than a precept of commonsense born of experience
and the instinct of self-preservation; for, as Polybius very clearly puts
it (lib. i. cap. 83): "Nor is such a principle to be despised, nor should
so great a power be allowed to any one as to make it impossible for you
afterwards to dispute with him on equal terms concerning your manifest
rights." It was not, however, till the beginning of the 17th century, when
the science of international law took shape at the hands of Grotius and his
successors, that the theory of the balance of power was formulated as a
fundamental principle of diplomacy. According to this the European states
formed a sort of federal community, the fundamental condition of which was
the preservation of the balance of power, _i.e._ such a disposition of
things that no one state or potentate should be able absolutely to
predominate and prescribe laws to the rest; and, since all were equally
interested in this settlement, it was held to be the interest, the right
and the duty of every power to interfere, even by force of arms, when any
of the conditions of this settlement were infringed or assailed by any
other member of the community.[1] This principle, once formulated, became
an axiom of political science. It was impressed as such by Fenelon, in his
_Instructions_, on the young duke of Burgundy; it was proclaimed to the
world by Frederick