In the fleet-ship, likewise the ship of the line, as the opening century styled the class of vessel known in the closing days as the battle-ship, our predecessors had reached a mean conclusion. The line-of-battle ship, or the ship of the line, as more usually called, differed from the frigate generically, in that it had two or more covered decks. There were one or two cases of ships with four decks, but, as a rule, three were the extreme; and ships of the line were roughly classed as two or three deckers. Under these heads two-deckers carried in their two centuries of history from fifty to eighty-four guns; three-deckers from ninety to one hundred and twenty. The increase in number of guns, resulting, as it did, from increase of size, was not the sole gain of ships of the line. The bigger ships got, the heavier were their timbers, the thicker their planking, the more impenetrable, therefore, their sides. There was a gain, in short, of defensive as well as offensive strength, analogous to the protection given by armor. “As the enemy’s ships were big,” wrote a renowned British admiral, “they took a great deal of drubbing.” Between the great extremes of strength indicated by fifty and one hundred and twenty guns—whose existence at one and the same time was the evidence of blind historical development, rather than of intelligent relative processes—the navy of a century ago had settled upon a mean, to appreciate which the main idea and purport of the ship of the line must be grasped. The essential function of the ship “of the line” was, as the name implies, to act in combination with other ships in a line of battle. To do this was needed not only fighting power, but manœuvring ability—speed and handiness—and in order that these qualities might approach homogeneousness throughout the fleet, and so promote action in concert, the acceptance of a mean type was essential. To carry three decks of guns, a ship had to expose above water a side disproportionately high relatively to her length, her depth, and her hold upon the water. She consequently drifted rapidly when her side was turned to the wind; while, if her length was increased, and so her hold on the water, she needed more time and room to tack and to wear—that is, to turn around. Ships of this class also were generally—though not necessarily—slow. ADVANTAGES OF THE SEVENTY-FOURS