The destroyer _Mohawk_, built by J. Samuel White at Cowes, is 270 feet in length, 25 feet beam, and 765 tons displacement, and contains water-tube boilers and turbines of 14,000 horse-power, and attained a speed of forty miles an hour. She carries no coal, oil fuel being used, of which her bunkers can take seventy-three tons. The _Tartar’s_ record was broken by the destroyer _Swift_, 345 feet in length with a displacement of 1800 tons, and having quadruple turbine engines giving her a speed of 36 knots. The cruiser _Invincible_, launched by Armstrongs at Elswick in April 1907, is a first-class armoured cruiser 530 feet in length and of 17,250 tons displacement, and has turbine engines of an equivalent horse-power of 40,000 and a speed of 25 knots. [Illustration: _Photo. G. West & Son._ H.M.S. “LORD NELSON.”] [Illustration: _Photo. G. West & Son._ H.M.S. “INVINCIBLE,” ARMOURED CRUISER.] The construction of warships has resolved itself into a struggle to attain an ever-increasing speed combined with offensive power and great range of action, and warships of varying types have been produced with startling rapidity, so that one powerful vessel after another has been evolved, each superseding its predecessor in some degree, until there are “Dreadnoughts” and “Super-Dreadnoughts” carrying guns and armour and possessing a speed undreamt of a few years ago. Among smaller vessels, torpedo-boats, destroyers, scouts, cruisers of various classes, commerce destroyers, cruiser-battleships, and submarines now take their places in the nation’s fleet. There is no telling in what direction the next development will be. The battle of the boilers has played an important part in the development of the warship, and it is safe to say that had this struggle not taken place to produce a boiler which should give a great pressure of steam quickly, the speed of the warship as now known would not have been attainable. Twin screws are succeeded by triple screws, and these are to be followed by quadruple screws.