Yet all the same the value of submarines is universally acknowledged and every great navy has them. They will probably prove useful in planting that new instrument of destruction, the floating mine, about which a few words must be said here: “It is to be presumed,” writes Reventlow, “that in the next naval war [how little he dreamed in November, 1913, that that war was so close at hand!] mines will play an important part not merely in coast defense but also in sea fights as a weapon with the same justification as artillery and torpedoes and that their use will materially influence the tactics to be employed.” As such a weapon of attack mines were first used in the Japanese-Russian War. [Illustration: A Submarine Flotilla] [Illustration: Torpedo Boat] [Illustration: Search Lights] [Illustration: A Submarine About to Dive] A mine, as the reader probably knows, is a cask filled with high explosives and fastened by means of weights and anchors so that it floats some feet below the surface. Mines can be planted in fields, as it were, by torpedo-boats or submarine and then a hostile fleet can be lured or chased in among them. The North Sea, as we know, is at present thickly strewn with them and fatal results have already been chronicled. Air-ships and aeroplanes can help by finding the whereabouts of the hostile fleet and designating by wireless the spots where the mines should be planted. Air-ships and aeroplanes will possibly find their chief use as coast-defenders. They need refuges to which they can retire, which limits their use on the high seas. But along the shore they can scout for hostile ships and also can detect submarines and mines. They can throw down explosives and, if they are near enough to the enemy’s harbors, can destroy docks and demoralize shipping. Already there is talk of specially armored decks and of great iron grills for protecting the openings of funnels. * * * * * More than six months ago a thoughtful German, Rudolf Troetsch, wrote a book called _Germany’s Fleet in the Decisive Struggle_, in which he weighs the different tasks the fleet will be called upon to perform in case of war, and comes ever and again to the conclusion that a battle on the high seas is the only possible option—a battle _im grossen Stile_, in the grand style. Even if the enemy’s fleet is not conquered it can be greatly weakened and strategy and tactics will go far to make up for want of numbers.