Fig. 3 is a sectional view of one of the engines of the new cruiser. Fig. 4 shows the ar rangement of the three engines in a plan view: Fig. 5 is a transverse section aft of the two forward engines; Fig. 6 is a plan view; and Fig. 7 an end view showing the position of the three screws.
The steamer WM. constructed by Dnusmuir & Jackson. Glasgow, for passenger service on one of the rivers on the Bombay coast, India, is 90 ft. long by 20 ft. broad, and 3 ft. :3 in. draft. when fully loaded. The propelling engine (Fig. 8) is a vertical, three-cylinder, triple expansion, surface-condensing engine, placed athwart the vessel, each cylinder forming a separate engine, and driving its own crank-shaft and propeller, the three engines being con nected together by two sure-rods. The cylinders are 9, 14} and 25 in. diameter and 10 in. stroke. They are designed for a pressure of 200 lbs. per sq. in., and to run 300 revolutions per min. The propellers are of gun-metal, each 2 ft. 6 in. diameter, with three blades. The cen ter screw is placed in the usual aperture in the stern, and the two outside screws a few feet farther forward. (Engineering, Aug. 21, 1891, p. 211.) Quadruple-Eirponsion, Engines for Torpedo-.Boak—Messrs. Yarrow & Co. recently built six first-class torpedo-boats for the Argentine navy, 130 ft. long and 13 ft. 6 in. wide on the water-line. The first five were fitted with triple-compound engines, and on their official trials of two hours' continuous run, and fully equipped for service, attained speeds of somewhat over 23 knots per hoar, the mean of all the trials being 23.312 knots. The sixth boat, called the Ilathurst, was fitted with a quadruple-compound The cylinders arc 14 in., 20 in., 27 in., and 36 in. diameter, and have a stroke of 16 in. The order of position is high, second in termediate, first intermediate, and low. The valves are all of the piston type. The chief object in view in placing quadruple-expansion engines in this boat was to do away with, or perhaps rather to materially reduce, the vibration that is so unpleasant a feature in modern high-speed craft with quick-running engines. A very fair measure of success has been at tained in this direction, sufficient to warrant the extra room mind expense due to the introduc tion of the additional cylinder. Under the same conditions of consumption the average horse power of five first-class boats with triple-compound engines was 1,120, indicated ; while on the Bathurst 1.230 indicated horse-power has been registered ; so that there was a gain of 110 indicated horse-power. (In the trial the mean speed was 24.453 knots, while on the two hours'
run the speed was but a trifle less-21.426 knots. There is therefore a gain of over a knot, presumably due to the additional cylinder. The load. carried was 12 tons, and the displace ment 75-5 tons. The steam-pressure wax 200 lbs.; first receiver. 75 lbs.; second receiver. :ti lbs.; third receiver, 4 lbs, Forced draft was used, the air-pressure in the stokchold averaging 3.2 ins. The engines made about 431 revolutions per min. (See Engineering, Nov. 21. 1800.) 11. MsitisE-Exuisamttxu. Pitommss IN.—Mr. Alfred Blechyuden. of Barrow-in-Furness, England. contributed a highly interesting. illustrated paper on 31arine-Engineering to the lAverpool meeting of the Institution of Mechanical Engineers, 1891 (see Engineering, A n g. 21 and Sept. 18, 1891), giving at review of progress during the last decade. We shill abstract liberally from his paper in what follows: Since 1881 the three-stage expansion-engine has become the rule, and the Imiler-pressure has been increased to 160 lbs. and even as high as 200 lbs. per sq. in. Pour-stage expansion engines of various forms have also been adopted. The increase of working pressure and other improvements hare brought with them their equivalent in economy of void. which is about 20 per Vent. Marked progress has been made in the direction of dimension, more than twice the newer having been putt into individual vessels.
Forred brafl,—There are several methods by which the prineiple known as ftweed draft may be pistol ieally applied. In its earlier English use stoke-holds were adopted, the air being delivered into them by flolF, RI a pressure varying from abont 1 in. to in. of water. This tirrangeinent has t he merit of keeping the stoke-holds and its details are simple; but it is dirty, and where bunker-doers mire not well fitted great diseettifort stay be paused on deck. Possibly, also, it is um quite so eeonomical as the (dosed ash-pit system : but such exact data MI exist of its working itelieate that with moderate nir-pressure it ix at least no less economical than natural draft. The Awl-item practice is to dose the ash-pits. and take the delivery tubes t lie fans into them, This, though involving more ash-pit fittings, is certainly ad vantageous se far as ehettniness is VoueVruui : the furnares are also not suljeetedl to the severe strains caused by the inrush of cold air which oecnrs during firing with closed stoke-holds.