TUAKSACTIOXS OF SECTION G. 673 



recognised position wliieli tlie torpedo-boat liad now attained as an engine of 

 warfare. 



He then described, in detail, with the aid of models and diagrams, the two 

 distinct groups into which the various types of torpedo-boats have gradually been 

 resolved, viz., those attached to and carried by larger vessels, to which they "would 

 act as auxiliaries ; and those sufficiently large to act independently, aiid. to a 

 certain extent, to keep the sea, which would be used for harbour and coast defence. 

 These two groups have been named, by the English Admiralty, the first and 

 second-class groups, respectively. 



The dimensions of the present English second-class boats are: — Length, over 

 all, 08 ft._; beam, 7 It. G in. ; draught of water, 3 ft. 4 in. ; displacement, 12^ tons. 

 The hull is constructed of Bessemer steel, galvanised, and is divided into ten com- 

 partments by means of bvdkheads and half-bulkheads. The machinery consists of 

 a pair of compound surface condensing-engines, having cylinders 8^ in. and 13 in. 

 diameter respectively, by 8 in. stroke; giving 150 indicated horse-power at a 

 speed of 653 revolutions per minute, corresponding to 17-65 knots per hoiu-, the 

 maximum measured-mile speed attained by these boats. The surface condenser is 

 of copper, tinned inside, and the condensing water is supplied by means of a 

 centrifugal pump 8 in. diameter, driven by a separate engine. The boiler is of the 

 locomotive type, the shell being made of steel with a copper fire-box and brass 

 tubes, strong enough to withstand a water-pressure of 260 lbs., and a working 

 pressure of 130 lbs. per sq. in. The area of the fire-grate is 66 sq. ft., and the 

 heating surface 2(38 sq. ft. The stokehold is entirely enclosed, and the air is 

 supplied to the boiler by means of a fan, driven by an independent engine, which 

 at a speed of 800 revolutions per minute gives a pressure of fi-om 2 to 3 in. of 

 water. The stokers are kept cool and comfortable by the large volume of air 

 passing through, and to provide for their safety the fire-door of the boiler is made 

 to shut tight ; the ash-pan is cased in with a light casiug, having flaps in front 

 opening inwards, which woidd close on any undue pressure, such as would arise 

 from the bursting of a tube or other sudden leakage in the boiler; and an escape, 

 closed at normal pressure by a door fostened by a sprmg, is carried up to the deck. 

 By means of a nozzle fitted into the bottom pa'rt of the barrel of the boiler, and a 

 pipe carried to the deck, the boiler of the boat can be connected with the ship's 

 boiler, and a steam-pressure of 60 lbs. raised in about 9i minutes, by which time 

 the fiin, also driven by the borrowed steam, has brought "the fire into condition to 

 maintain that pressure. 



These boats are fitted with an ejector in the stokehold, capable of ejecting 45 

 tons of water per hour. The centrifugal pump can be utiUsed for emptying the 

 bilges, and the two together would eject the whole displacement of the boa'ts every 

 ten minutes. The lifting weight of the boats all on board is ]2|- tons, and the 

 lifting is eftected by means of slings, attached to hoops on the bidkheads forward 

 of the boiler-room and aft of the engine-room. 



The second-class boats, built or building by tlie author's firm for the Danish 

 and Italian Governments, are substantially the same as the English second-class in 

 Imll, engines and boilers ; but in the Danish boats the pumping is done by ejectors 

 alone, six of which are fitted in different parts of the boat, and are capable of 

 ejecting the whole displacement every 6f minutes. The ease and readiness with 

 which an ejector can be turned on in any compartment without the necessitv of 

 communicating with the engine-room are a strong recommendation in favour of that 

 method of pumping. All second-class boats now carry two 14-in. Whitehead torpe- 

 does, and the Danish and Italian also carry two-barrelled Gardner machine-guns. 



There are three methods of ejecting the torpedoes. The earlier English'" boats 

 are fitted with davits and di.'=charging frames, so arranged that the frames can be 

 lowered over the side, close to the boat and parallel to its centre line, to a depth of 

 2 ft. under the surface of the water. In this system no external impulse is used- 

 the pulling of a lanyard liberates the torpedo and starts its engine. 



This sy.stem has been superseded in the later English boats, in which the 

 torpedoes are laid all ready for discharging in two troughs on the forward part of 

 the deck, and are projected therefrom by means of two pistons and rods working 

 1882. X X 



