3.--They should be extremely handy. 4.--No smoke should enable their approach to be detected, or glare from their fires. 5.--That it should be possible to raise steam in them in a few minutes. 6.--They should be built in water-tight compartments, and covered fore and aft to prevent being swamped. 7.--The crews should be protected as far as practicable from rifle fire. In addition to the foregoing, for the purpose of rendering these craft capable of defending themselves against the attack of guard boats, and also of being employed as such, and on river expeditions, &c., they should be built sufficiently strong to enable them to carry a small gun either in the bows or stern; this would apply more especially to those torpedo boats which are part of a ship's stores. During the last four years a very large number of torpedo boats have been built, which more or less fulfil the aforesaid conditions, nearly the whole of which have been constructed by the two English firms, viz. Messrs. Thornycroft and Co. and Messrs. Yarrow and Co., and to the latter firm is due the honour of constructing the fastest vessel as yet in the world. Up to the present time, a specially built torpedo boat has on only one occasion been used on active service, viz. at the attack on a Turkish monitor on the 20th of June, 1877, which is detailed at length in the following chapter. This boat was one of Messrs. Thornycroft and Co.'s launches, and from all accounts she behaved wonderfully well under the most untoward circumstances. _Thornycroft Torpedo Launches._--Messrs. Thornycroft and Co., of Chiswick, London, have during the last six years built a large number of torpedo launches for the English government and for several of the principal European governments. _Norwegian Launch._--The first torpedo boat ever built by this firm was the one shown at Fig. 150, for the Norwegian government. This boat was 57 feet in length by 7 feet 6 inches beam, drew 3 feet of water, and the stipulated speed was 16 English statute miles, or nearly 14 knots per hour; which speed was not to be ascertained by a mere measured mile trial, but was to be 16 miles through the water in a run of one hour's duration. The hull of the vessel was constructed entirely of steel plates and angle bars, and, as may be seen from the diagram, was divided into six water-tight compartments, _A_, _B_, _C_, _D_, _E_, _F_. The compartments marked _A_ and _F_ in the stem and stern were for stores; those marked _B_ and _E_ were fitted with seats for the crew, and were provided with movable steel covers, so that on going into action, or during rough weather, they might be completely covered. The compartments _C_ and _D_ are for the steersman and the machinery respectively, and were covered completely by steel plating 3/16 of an inch in thickness--a thickness sufficient to withstand Snider or Martini-Henry bullets, fired from a distance of twenty paces.