As matters stand now, the submarines are forced to return to their home ports to refill their fuel tanks, to take on fresh provisions for the men, and to replenish their exhausted ammunition and torpedoes. Thus, even though their personnel gets relief by the boat's halting upon the sea-bed, a cog is slipped in the matter of continued military efficiency. Without a fresh supply of fuel oil and more food and munitions of war the submarine is ineffective, and when her objective is a distant one she must draw heavily upon her stores to get her there and to carry her safely back to her revictualling base. Indeed, she may overreach herself through her commander's desire to strike his remote enemy and then find herself forced back to the surface and without the means to take her home again, floating impotently upon the sea, an easy target for attack, and certain to be sunk or captured. These present handicaps need not be permanent ones, and there is no more reason why a submarine should not take on fresh stores in the open sea than a surface vessel. Indeed, a submarine should be able to replenish her fuel tanks and to ship provisions under some circumstances even more securely than its rivals that run upon the water. In short, a submarine should be capable of sinking to the sea-bed and there, beyond the reach of its foes, of drawing new strength, so to speak, from a suitably designed submergible supply boat. This scheme is not at all visionary. In part it has already been done in the past by vessels planned by me for commercial work, and there is no inherent difficulty in modifying both the military submarine and its revictualling consort so that they can thus function in unison for the purpose of giving the fighting undersea boat a wider field of action. While the torpedo-boat destroyer, the submarine's logical pursuer to-day, is battling with wind and wave, jarring well nigh her sides out, and hunting over the tumbling seas for elusive periscopes, the submarine can lie in ambush upon the ocean-bed if the water be not too deep, or at rest at any desired depth, held in suspension between the surface and the bottom by her anchors, thus conserving her energies so that when she does rise for a peep through her observing instrument she can strike more certainly with all of the sinister force of her chosen weapon of attack. She can lurk in wait for her quarry not only for one day but for weeks at a time, especially when sand banks a hundred feet below the surface offer the needful haven.