f motion or decrease
it at his will; he can reduce it to zero. He cannot do so with
the forces of nature.

_Directability_.--Not only can one man control the power of the
fleet, he can also direct it; that is, can turn it to the right
or the left as much as he wishes. But one man cannot change the
direction of motion of Niagara or the lightning-bolt.

_Power, Controllability, and Directability_.--We may say, then,
that a fleet combines the three elements of mechanical power,
controllability, and directability.

_The Unit of Military Power_.--This is an enormous power that has
come into the hands of the naval nations; but it has come so newly
that we do not appreciate it yet. One reason why we do not and cannot
appreciate it correctly is that no units have been established by
which to measure it.

To supply this deficiency, the author begs leave to point out that,
since the military power of every nation has until recently been
its army, of which the unit has been the soldier, whose power has
rested wholly in his musket, the musket has actually been the unit
of military power. In all history, the statement of the number of
men in each army has been put forward by historians as giving the
most accurate idea of their fighting value; and in modern times,
nearly all of these men have been armed with muskets only.

It has been said already that the main reason why the invention
of gunpowder was so important was that it put into the hands of
man a tremendous mechanical power compressed into a very small
space, which man could use or not use at his will. This idea may
be expressed by saying that gunpowder combines power and great
controllability. But it was soon discovered that this gunpowder,
put into a tube with a bullet in front of it, could discharge that
bullet in any given direction. A musket was the result, and it
combined the three requisites of a weapon--mechanical power,
controllability, and directability.

While the loaded gun is perhaps the clearest example of the combination
of the three factors we are speaking of, the moving ship supplies
the next best example. It has very much greater mechanical power;
and in proportion to its mass, almost as much controllability and
directability.

The control and direction of a moving ship are very wonderful things;
but the very ease with which they are exercised makes us overlook
the magnitude of the achievement and the perfection of the means
employed. It may seem