cial facilities by
the admiralty--what are the manoeuvring powers of ships propelled by
steam under varying conditions of speed and helm, he proceeded to devise
a system of tactics based on these data. In the sequel he prepared a new
evolutionary signal-book, which was adopted by the royal navy, and still
remains in substance the foundation of the existing system of tactical
evolutions at sea. The same series of experimental studies led him to
conclusions concerning the chief causes of collisions at sea; and these
conclusions, though stoutly combated in many quarters at the outset,
have since been generally accepted, and were ultimately embodied in the
international code of regulations adopted by the leading maritime
nations on the recommendation of a conference at Washington in 1889.

After his retirement Colomb devoted himself rather to the history of
naval warfare, and to the large principles disclosed by its intelligent
study, than to experimental inquiries having an immediate practical aim.
As in his active career he had wrought organic changes in the ordering,
direction and control of fleets, so by his historic studies, pursued
after his retirement, he helped greatly to effect, if he did not
exclusively initiate, an equally momentous change in the popular, and
even the professional, way of regarding sea-power and its conditions. He
did not invent the term "sea-power,"--it is, as is shown elsewhere (see
SEA-POWER), of very ancient origin,--nor did he employ it until Captain
Mahan had made it a household word with all. But he thoroughly grasped
its conditions, and in his great work on naval warfare (first published
in 1891) he enunciated its principles with great cogency and with keen
historic insight. The central idea of his teaching was that naval
supremacy is the condition precedent of all vigorous military offensive
across the seas, and, conversely, that no vigorous military offensive
can be undertaken across the seas until the naval force of the enemy has
been accounted for--either destroyed or defeated and compelled to
withdraw to the shelter of its own ports, or at least driven from the
seas by the menace of a force it dare not encounter in the open. This
broad and indefeasible principle he enunciated and defended in essay
after essay, in lecture after lecture, until what at first was rejected
as a paradox came in the end to be accepted as a commonplace. He worked
quite independently of Captain Mahan, and his