that things near the earth tend to fall to the earth; but he was the first to formulate and prove the doctrine of universal gravitation. In the same way, all through history, we find that a few master minds have been able to group what had theretofore seemed unrelated phenomena, and deduce from them certain laws. In this way they substituted reasoning for speculation, fact for fancy, wisdom for opportunism, and became the guides of the human race.

The effect of the acceptance of Mahan's doctrine was felt at once. Realizing that the influence of sea power was a fact, comprehending Great Britain's secret, after Mahan had disclosed it, certain other great nations of the world, especially Germany, immediately started with confidence and vigor upon the increase of their own sea power, and pushed it to a degree before unparalleled; with a result that must have been amazing to the man who, more than any other, was responsible for it.

Since the words "sea power," or their translation, is a recognized phrase the world over, and since the power of sea power is greater than ever before, and is still increasing, it may be profitable to consider sea power as an entity, and to inquire what are its leading characteristics, and in what it mainly consists.

There is no trouble in defining what the sea is, but there is a good deal of trouble in defining what power is. If we look in a dictionary, we shall find a good many definitions of power; so many as to show that there are many different kinds of power, and that when we read of "power," it is necessary to know what kind of power is meant. Clearly "sea power" means power on the sea. But what kind of power? There are two large classes into which power may be divided, passive and active. Certainly we seem justified, at the start, in declaring that the power meant by Mahan was not passive, but active. Should this be granted, we cannot be far from right if we go a step further, and declare that sea power means ability to do something on the sea.

If we ask what the something is that sea power has ability to do, we at once perceive that sea power may be divided into two parts, commercial power and naval power.

The power exerted by commercial sea power is clearly that exerted by the merchant service, and is mainly the power of acquiring money. It is true that the merchant service has the power of rendering certain services in war, especially the power of providing auxiliary vessels, and of furnishing men accustomed to the sea; but as time goes on the power contributable by the merchant service must steadily decrease, because of the relatively increasing power of the naval service, and the rapidly increasing difference between the characteristics of ships and men suitable for the merchant service and those suitable for the naval service.

But even in the past, while the importance of the merchant service was considerable in the ways just outlined, it may perhaps be questioned whether it formed an element of sea power, in the sense in which Mahan discussed sea power. The power of every country depends on all the sources of its wealth: on its agriculture, on its manufacturing activities, and even more directly on the money derived from exports. But these sources of wealth and all sources of wealth, including the merchant service, can hardly be said to be elements of power themselves, but rather to be elements for whose protection power is required.

In fact, apart from its usefulness in furnishing auxiliaries, it seems certain that the merchant service has been an element of weakness. The need for navies arose from the weakness of merchant ships and the corresponding necessity for assuring them safe voyages and proper treatment even in time of peace; while in time of war they have always been an anxious care, and have needed and received the protection of fighting ships that have been taken away from the fleet to act as convoys.

If commercial sea power was not the power meant by Mahan, then he must have meant naval power. And if one reads the pages of history with patient discrimination, the conviction must grow on him that what really constituted the sea power which had so great an influence on history, was naval power; not the power of simply ships upon the sea, but the power of a navy composed of ships able to fight, manned by men trained to fight, under the command of captains skilled to fight, and led by admirals determined to fight. Trafalgar was not won by the merchant service; nor Mobile, Manila, or Tsushima.

If sea power be essentially naval power, it may be interesting to inquire: In what does naval power consist and what are its principal characteristics?

If one looks at a fleet of war-ships on the sea, he will be impressed consciously or unconsciously with the idea of power. If he is impressed consciously, he will see that the fleet represents power in the broadest sense—power active and power passive; power to do and power to endure; power to exert force and power to resist it.

If he goes further and analyzes the reasons for this impression of power, he will see that it is not merely a mental suggestion, but a realization of the actual existence of tremendous mechanical power, under complete direction and control.

In mechanics we get a definition of power, which, like all definitions in mechanics, is clear, definite, and correct. In mechanics, power is the rate at which mechanical work is performed. It is ability to do something in a certain definite time.

Now this definition gives us a clear idea of the way in which a navy directly represents power, because the power which a navy exerts is, primarily, mechanical; and any other power which it exerts is secondary and derived wholly from its mechanical power. The power of a gun is due wholly to the mechanical energy of its projectile, which enables it to penetrate a resisting body; and the power of a moving ship is due wholly to the mechanical energy of the burning coal within its furnaces.

It may be objected that it is not reasonable to consider a ship's energy of motion as an element of naval power, in the mechanical sense in which we have been using the word "power," for the reason that it could be exerted only by the use of her ram, an infrequent use. To this it may be answered that energy is energy, no matter to what purpose it is applied; that a given projectile going at a given speed has a certain energy, whether it strikes its target or misses it; and that a battleship going at a certain speed must necessarily have a certain definite energy, no matter whether it is devoted to ramming another ship or to carrying itself and its contents from one place to another.

Besides the mechanical power exerted by the mere motion of the ship, and often superior to it, there is the power of her guns and torpedoes.

Perhaps the most important single invention ever made was the invention of gunpowder. Why? Because it put into the hands of man a tremendous force, compressed into a very small volume, which he could use instantaneously or refrain from using at his will. Its first use was in war; and in war has been its main employment ever since. War gives the best field for the activity of gunpowder, because in war, we always wish to exert a great force at a definite point at a given instant; usually in order to penetrate the bodies of men, or some defensive work that protects them. Gunpowder is the principal agent used in war up to the present date. It is used by both armies and navies, but navies use it in larger masses, fired in more powerful guns.

Of course this does not mean that it would be impossible to send a lot of powder to a fort, more than a fleet could carry, and fire it; but it does mean that history shows that forts have rarely been called upon to fire