carefully designed to cut through the water, but it is not so apparent that the stern must also be shaped to permit the water to flow in readily and fill in the void behind the ship. If the stern is not carefully shaped, there will be a serious drag on the vessel. The skin friction of the vessel is greatly increased by fouling of the hull with marine growths. At high speeds the wind pressure on the superstructure is considerable. Every spar and line adds its quota. A boat that is traveling in still air at a speed of twenty-two knots or twenty-five miles per hour is encountering the equivalent of a twenty-five mile wind which will exert a pressure of over three pounds per square foot of frontage. FLYING ON WATER Instead of cutting through the water modern speed boats are designed to ride over it. The boats have flat bottoms which are arranged as a series of flat planes known as hydroplanes. These planes form steps and are set at such an angle as to make the boat rise up on the water in the same way that a kite rises in the air. The higher the speed the higher the boat rises so that at full speed it skims on the surface. Hence there is comparatively little power wasted in displacing the water. Some of these boats are driven by air propellers so that water resistance to the propeller gear is avoided. These hydroplanes (they must not be confused with hydroaeroplanes) almost fly over the water. FIRST OCEAN STEAMER It was in 1807 that Robert Fulton built the _Clermont_ and established steam navigation by running a regular service between New York and Albany, and it was twelve years later that the Atlantic Ocean was first crossed by a steam-driven vessel. It was an American vessel, the _Savannah_, that made the trip. She was a 380-ton ship equipped with steam power to help her along when the wind failed. Seventy-five tons of coal and twenty-five cords of kindling wood were taken aboard to feed her furnace. This was thought to be ample for the voyage, but before the trip was completed the fuel was all gone. The log of the _Savannah_ bears this entry the night before sighting the Irish coast: “2 A. M. Calm. No cole to get up steam.” However the captain did raise steam just before reaching Kinsale, Ireland, by burning wood. Watchers ashore beholding the smoke issuing from her stack were convinced that the vessel was afire and boats were dispatched to the rescue. The _Savannah_ made the trip from Savannah to Kinsale in 23 days and was under steam propulsion for only 80 hours of this time. Regular trans-Atlantic steam service was not inaugurated until 1838, but for many decades steamers were equipped with sails to assist them when the wind was favorable.