OSCILLATING ENGINES.

The remaining portion lastly to be consi-dered is, the connection of the plunger and themode of motion. Two universal means forimparting the action are in practice at present,either by the vibration of the cylinder, or theoscillation of the trunnion.

The illustration first under notice illustratesthe plunger connected, by hollow and solid rods,to an arm secured to the steam belt on thecylinder. A key is inserted in the rod directlyabove the plunger, to preserve the motion, andon its withdrawal, the plunger ceases to act.

By Fig. 55—page 225—an arrangement ofthe pumps last under notice is shown. Thevalves are on each side of the plunger, andthe motion for the latter is derived from anarm keyed on the trunnion—the arms beingduplicate—on each side the trunnion, a reverseaction for the pumps is the result.

The modes of motion thus far alluded to areadopted by Messrs. J. Penn and Son, Messrs. James Watt and Co., Messrs. Ravenhill andHodgson, Messrs. J. and Gf. Bennie, and otherfirms of eminence.

Apart from these, the Messrs. Maudslay, Sons,and Field claim notice, in relation to themeans of working the pumps under notice.

In page 218 an illustration is given of anexpansion gear, the eccentric of which im-parts motion also to the feed and bilgepumps. One pump only is represented, angu-larly secured, at the side of the trunnionplummer block. The connection of theplunger is as that for Fig. 64—page 234—fiut a set screw is used, in the place of a key,as a means of release. The valve box is bolted!o the flange at the base of the pump, whichsituation is not as available for perfection of

action as the top of the barrel. It needs nogreat enquiry as to this fact, and more parti-cularly so, when it is remembered that airnaturally ascends, and when compressed, witha velocity due to the pressure occasioned. Itcan thus be readily understood that the properplace for the discharge valve of any pump isabove the plunger.

SUPPLEMENTARY VALVES.

INJECTION VALVE.

The detail first to be alluded to as the mostimportant is the injection valve. The utilityof this addition to the condenser is, of course,as well understood, to regulate the amount ofwater requisite to condense the steam. Thesevalves are mostly of two kinds, generallyFig. 65.

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INJECTION PLUG VALVE.

either a gridiron or a plug—more often thelatter—to which especial reference is made

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