MARINE ENGINES.

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practical purposes. The doors in, the arrangement of condenserunder notice only admit of inspecting one end of the tubes; forpacking their central ends a manhole is arranged in the bottomand top chambers, through which the water enters the tubes at thebottom, and from which it is discharged overboard at the top. Aplate abutting on both tube plates forms the division between thetwo. This arrangement is very good for engines of large power, asthe tubes are of a suitable length, neither too long nor too short.

To facilitate the water from the Condensed steam flowing awayfrom the tubes, when condensation takes place on their internalcircumference, the tubes have been arranged lying at an angle.They may be so disposed right and left, or all in a cluster; whenarranged right and left, the central chamber, as in the foregoingexample, becomes the exhaust steam chamber, instead of the waterchambers. The air pumps are arranged on each side of the outerframes of the engine, and the circulating pumps on each side of thecentral frame; the suction valves for both pumps are inverted andplaced above the pumps, while the discharge valves are arrangedalongside, the circulating water flowing amongst the tubes at thebottom end near the central frame, and ejected from the vesselcontaining the tubes at the opposite corner at the top: thus thewater is well distributed amongst the tubes—a very necessary thingto attend to in all arrangements.

The valves for the pumps are of the round disc type, made ofindia rubber, having grated seatings and guards of brass. Some ofthese valves fold up all round against a saucer-shaped guard per-forated with holes, and are secured to each hole in the condenserby a cross bar of iron and a single bolt. This bolt passes throughthe centre of the bar, seating, and guard, and is secured with onenut at the top, pressing the guard and seating downwards, anddrawing the cross bar upwards against the under side of the metalsurrounding the hole in the condenser casting; but the general wayis to secure the guard and valve by a screwed stud with a nut atthe top to a large plate containing all the gratings for valves, theplate being secured over one large hole in the condenser casting bygun-metal stud bolts and nuts. Sometimes the guards are madequite flat, the valve moving upwards and downwards on the bossof the guard, the central hole in the india-rubber disc being madeslightly larger, so that it moves easily; this arrangement can be

secured with a cross bar, or with stud bolts, on a plate common to

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