The two-decked ship was superior in speed and in handiness, and for that reason, even when acting singly, she could put forth such power as she possessed more quickly and more certainly. But these qualities were most conspicuously valuable when ship had to act with ship. The great secret of military success, concerted action in masses, was in the hands of the two-decked ship, because in her were united to the highest point individual power and facility for combined action. And this was true not only of two-deckers in general, but of the particular species known as the seventy-four-gun ship. Ships below that rate lacked individual fighting power. Ships above it, the eighty and eighty-four, lost manœuvring power because of their greater length and weight. Under the conditions of sail a fleet of seventy-fours could get out the whole power of the force more surely and more rapidly than the equivalent number of guns in ships of any other kind. Thus offensive power dictated its survival. To our own day it reads the lesson that offensive power, the _sine quâ non_ of a military organization, lies not merely in the greatest strength of the single ships, but in the uniformity of their action and rapidity of their movements, as conducive to the quick putting forth of the strength of the whole body at once and in mutual support. It may be asked naturally, why, then, were there any ships bigger or smaller than this favored type? For smaller, the answer is that short ships of lighter draught are best suited for shoal or intricate navigation. The shoals of Holland forbade heavy ships to the Dutch navy, materially reducing its fighting strength. Before France entered our Revolutionary struggle the British sent only sixty-fours to operate upon our comparatively shallow coasts and bars. As regards bigger ships, they were useful exceptionally, as were forty-four-gun frigates, and for the following reason: Every line of battle has three particularly dangerous points—the centre, because there the line, if pierced, divides into the two smaller fragments; and the flanks, or ends, because the extremities are supported less easily by the rest of the force than the centre is, one extremity being farther from the other than the centre is from either. Such local weakness could not be remedied by the use of two ships, for, if the line were properly closed, one of them could fire at the enemy only through or over the other. The sole way of giving the strength there required was by concentrating it into individual ships, either by putting on the additional battery, which gives a three-decker, or by making the seventy-four heavier, resulting in an eighty-gun ship on two decks. These stronger vessels were, therefore, stationed in the centre or on the flanks of a line of battle. The particular functions, the _raison d’être_, of the three leading classes of ships of war—the sloop, the frigate, and the ship of the line—have now been stated. It remains to