The most characteristic feature of the Lake submarines is not the wheels, which are found only on those specially designed for bottom working, but the hydroplanes. These are horizontal rudders that are so placed and designed as to steer the boat forward and downward, but at the same time keeping it on an even keel. Bushnell and Nordenfeldt forced their boats straight up and down like buckets in a well, John P. Holland made his tip up its tail and dive like a loon, but Mr. Lake conceived the idea of having his boat descend like a suitcase carried by a man walking down-stairs: the suitcase moves steadily forward and downward towards the front door but it remains level. The first method with its vertical propellers wasted too much energy, the second incurred the risk of diving too fast and too deep, no matter whether the single pair of horizontal rudders were placed on the bow, or amidships, or on the stern. So Mr. Lake used two pairs of horizontal rudders “located at equal distances forward and aft of the center of gravity and buoyancy of the vessel when in the submerged condition, so as not to disturb the trim of the vessel when the planes were inclined down or up to cause the vessel to submerge or rise when under way.” These he called hydroplanes, to distinguish them from another set of smaller horizontal rudders, which at first he called “leveling-vanes” and which were not used to steer the submarine under but manipulated to keep her at a constant depth and on a level keel while running submerged. In theory, the early Lake boats were submerged on an even keel; in practice, they went under at an angle of several degrees. But they made nothing like the abrupt dives of the _Holland_. “As the Electric Boat Company’s boats (Holland type) increased in size,” declares Chief Constructor D. W. Taylor, U.S.N., “bow rudders were fitted, and nowadays all submarines of this type in our navy are fitted with bow rudders as well as stern rudders. The Lake type submarines are still fitted with hydroplanes. But as you may see, means for effecting submergence have approached each other very closely: in fact, speaking generally, submarines all over the world now have two or more sets of diving-rudders; the most general arrangement is one pair forward and one pair aft; in some types three pairs are fitted, but this arrangement is more unusual. “In general it may be said then that modern submarines of both types submerge in practically the same way. They assume a very slight angle of inclination, say a degree and a half or two degrees, and submerge at this angle. This may be said to be practically on an even keel.” [Illustration: Courtesy of International Marine Engineering. Cross-section of the _Protector_, showing wheels stowed away when not running on the sea bottom.] The credit of originating this now world-wide practice of “level-keel submergence” obviously belongs, as “Who’s Who in America” gives it, to