In considering the development of the modern warship attention naturally turns to the battleship, but it should be remembered that other vessels of scarcely less importance help to constitute the modern navy, the most notable being the cruisers of various classes, the destroyers and torpedo boats, and submarines. Broadly speaking, the cruiser of the present day is to the modern fleet what the frigate was to the line-of-battle ship in the days of the three-deckers. That is to say, she has to be the eyes of the fleet, able to show a good turn of speed, and capable of taking care of herself if need be. There the resemblance ends. The duties of the modern cruiser are multifarious. She has to be no less a commerce protector than a commerce destroyer, and while at one end of the scale she may be little more than a glorified gunboat, she may at the other end have to be able to take her place in the line of battle and help her more powerful sisters. Whatever her duties, speed is regarded as of great importance. The _Iris_, in 1878, attained a speed of eighteen and a half knots, but more than seventeen years elapsed before this speed was equalled by any of the cruisers. Her sister ship, the _Mercury_, covered nearly 18.9 knots, or close upon twenty-two miles an hour. In 1895 the cruisers _Amphion_ and _Arethusa_ proved themselves able to exceed their designed speed of seventeen and a half knots, and thence onwards the increase in speed has been continuous, until we have the _Invincible_ in the British Navy capable of exceeding twenty-nine knots under service conditions and in only moderately fine weather, and the _Von der Tann_, in the German navy, possessing a speed of twenty-eight knots under the most favourable conditions of weather and lightness of stores. At one time the German ship was asserted to be the fastest large cruiser afloat, but her supremacy, if it ever existed, in this respect was very short-lived. The _Phæton_ was one of the last class of cruisers to be given square sails. Her canvas certainly proved useful to her, for her machinery broke down during her commissioning trials preparatory to the naval review at Spithead in 1897, and had it not been for her sails she would have been totally disabled. The incident was seized upon by those who still favoured the older methods which had done duty for so many hundreds of years, as an argument for the retention of sail power for the ships of the Royal Navy, and the modernists replied that such incidents were few and far between, and with the improvements in mechanism which science was continually making would become virtually impossible.