At full speed. At 10 knots. Battleships 55 per cent. 79 per cent. Cruisers 55 ” 84 ” Torpedo-boat destroyers 43 ” 80 ” The above table gives the percentage which the skin friction forms of the total resistance, and the remainder is, of course, wave-making and eddy-resistance. The curves shown in Fig. 41 (taken, by kind permission of the editor, from an article by Mr. E. H. Tennyson-D’Eyncourt, in _Cassier’s Magazine_ for November, 1901) give, in a diagrammatic form, an idea of the manner in which the two principal sources of ship-resistance vary with the speed. [Illustration: FIG. 41.—(Reproduced, by permission, from _Cassier’s Magazine_.)] It will be seen that when a ship is going at a relatively slow speed, the greater portion of the whole resistance is due to skin friction, but when going at a high speed, the greater portion of the resistance is due to wave-making. Hence the moral is that ships and boats intended to move at a high speed must be so fashioned as to reduce to a minimum the wave-making power. In general, the naval architect has to consider many other matters besides speed. In battleship design he has to consider stability, power of carrying guns and armour, and various other qualities. In passenger-steamers he has to take into consideration capacity for passengers and freight, also steadiness and sea-going qualities; and all these things limit and control the design. There is one class of vessel, however, in which everything is sacrificed to speed, and that is in racing-yachts. Hence, in the design of a racing-yacht, the architect has most scope for considerations which bear chiefly upon the removal of all limitations to speed. A little examination, therefore, of the evolution of the modern racing-yacht shows how the principles we have endeavoured to explain have had full sway in determining the present form of such boats. Attention has chiefly been directed to this matter in connection with the international yacht race for the possession of the America Cup. In 1851 a yacht named the _America_ crossed the Atlantic and made her appearance at Cowes to compete for a cup given by the Royal Yacht Squadron. Up to that time British yachts had been designed with full bluff bows and a tapering run aft. These boats were good sea-boats, but their wave and eddy making powers were considerable. The _America_ was constructed with very fine lines and a sharp bow, and was a great advance on existing types of yacht. In the race which ensued the _America_ won the cup, and carried it off to the United States. Since that date there has been an intermittent but steady effort on the part of British yachtsmen to recover the trophy, so far, however, without success. [Illustration: AMERICA, 1851. VIGILANT, 1893. PURITAN, 1885. DEFENDER, 1895. VOLUNTEER, 1887. COLUMBIA, 1899.