the Great in his _Anti-Machiavel_; it was re-stated with
admirable clearness in 1806 by Friedrich von Gentz in his _Fragments on the
Balance of Power_. It formed the basis of the coalitions against Louis XIV.
and Napoleon, and the occasion, or the excuse, for most of the wars which
desolated Europe between the congress of Muenster in 1648 and that of
Vienna in 1814. During the greater part of the 19th century it was obscured
by the series of national upheavals which have remodelled the map of
Europe; yet it underlay all the efforts of diplomacy to stay or to direct
the elemental forces let loose by the Revolution, and with the restoration
of comparative calm it has once more emerged as the motive for the various
political alliances of which the ostensible object is the preservation of
peace (see EUROPE: _History_).

An equilibrium between the various powers which form the family of nations
is, in fact,--as Professor L. Oppenheim (_Internat. Law_, i. 73) justly
points out--essential to the very existence of any international law. In
the absence of any central authority, the only sanction behind the code of
rules established by custom or defined in treaties, known as "international
law," is the capacity of the powers to hold each other in check. Were this
to fail, nothing could prevent any state sufficiently powerful from
ignoring the law and acting solely according to its convenience and its
interests.

See, besides the works quoted in the article, the standard books on
International Law (_q.v._).

(W. A. P.)

[1] Emerich de Vattel, _Le Droit des gens_ (Leiden, 1758).

BALANCE OF TRADE, a term in economics belonging originally to the period
when the "mercantile theory" prevailed, but still in use, though not quite
perhaps in the same way as at its origin. The "balance of trade" was then
identified with the sum of the precious metals which a country received in
the course of its trading with other countries or with particular
countries. There was no doubt an idea that somehow or other the amount of
the precious metals received represented profit on the trading, and each
country desired as much profit as possible. Princes and sovereigns,
however, with political aims in view, were not close students of mercantile
profits, and would probably have urged the acquisition of the precious
metals as an object of trade even if they had realized that the country as
a whole was exporting "money's worth" in order to buy the precio