upon the interior position of the Roman armies with reference to the
forces of Hasdrubal and Hannibal, was ultimately due to the fact that
the younger brother could not bring his succoring reinforcements by
sea, but only by the land route through Gaul. Hence at the critical
moment the two Carthaginian armies were separated by the length of
Italy, and one was destroyed by the combined action of the Roman
generals.

On the other hand, naval historians have troubled themselves little
about the connection between general history and their own particular
topic, limiting themselves generally to the duty of simple chroniclers
of naval occurrences. This is less true of the French than of the
English; the genius and training of the former people leading them to
more careful inquiry into the causes of particular results and the
mutual relation of events.

There is not, however, within the knowledge of the author any work
that professes the particular object here sought; namely, an estimate
of the effect of sea power upon the course of history and the
prosperity of nations. As other histories deal with the wars,
politics, social and economical conditions of countries, touching upon
maritime matters only incidentally and generally unsympathetically, so
the present work aims at putting maritime interests in the foreground,
without divorcing them, however, from their surroundings of cause and
effect in general history, but seeking to show how they modified the
latter, and were modified by them.

The period embraced is from 1660, when the sailing ship era, with its
distinctive features, had fairly begun, to 1783, the end of the
American Revolution. While the thread of general history upon which