STEAM NAVIGATION. 



ness of crank and a greater limitation of play of all the moving 1 

 parts in the vertical direction. The valves and the gearing by 

 which they are worked, the air-pump, the condenser and other 

 parts of the marine engines, do not differ in principle from those 

 already described in land engines. 



These arrangements will be more clearly understood by 

 reference to fig. 1, in which is represented a longitudinal 

 section of one of the many varieties of beam engine, with its 

 boiler as placed in asteam-vessel. The sleepers of oak, sup- 

 porting the engine, are represented at x, the base of the engine 

 being secured to these by bolts passing thrgugh them and the 

 bottom timbers of the vessel ; s is the steam-pipe leading from 

 the steam-chest in the boiler to the slides c, by which it is 

 admitted to the top and bottom of the cylinder. The condenser is 

 represented at B, and the air-pump at E. The hot well is seen at 

 F, from which the feed is taken for the boiler ; L is the piston-rod 

 connected by the parallel motion a, with the beam H, working on 

 a centre K, near the base of the engine. The other end of the 

 beam i drives the connecting rod M, which extends upwards to 

 the crank, which it works upon the paddle-shaft o. o, B. is the 

 framing by which the engine is supported. The beam here exhi- 

 bited is shown on dotted lines as being on the further side of the 

 engine. A similar beam similarly placed, and moving on the 

 same axis, must be understood to be at this side connected with 

 the cross-head of the piston in like manner by a parallel motion, 

 and with a cross-piece attached to the lower end of the connecting 

 rod and to the opposite beam. The eccentric which works the 

 slides is placed upon the paddle-shaft o, and the connecting arm 

 which drives the slides may be easily detached when the engine 

 requires to be stopped. The section of the boiler, grate, and flues 

 is represented at w u. The safety-valve y is enclosed beneath a 

 pipe carried up beside the chimney, and is inaccessible to the 

 engine man ; h are the cocks for blowing the salted water from 

 the boiler, and 1 1 the feed-pipe. 



12S 



