332 EXPLANATION OF THE PLATES. 



PLATE V. 



Fig. 1. is a section of a double-acting condensing engine, with a slide adapted 

 for working by the expanding force of steam ; the slide being, in Fig. 1., in the 

 position for letting the steam on at the top. Fig. 2. shows the steam shut oft', and 

 the passage to the condenser still open ; and Fig. 3. the position when the steam is 

 let on at the bottom. See art 448. The steam enters at S, and a pipe of com- 

 munication between the steam pipe and the condenser is necessary, to allow steam 

 to enter the condenser when the engine is about to be set to work, (art. 414.) 



Fig. 4. is a section of a single-acting condensing engine, with valves to the 

 passages, (see art. 406.) ; and Fig. 5. a different arrangement of the valves for a 

 single engine. 



Fig. 6. represents the box slide, admitting steam through the upper passage and 

 open below to the eduction passage, or to the condenser. 



In all these figures the same letters indicate the same parts. C is the steam 

 cylinder, P the steam piston, R the piston rod, B the condenser, with a jet of water 

 playing into it from I the injection cock ; A is the air pump, and p its piston ; 

 G is the foot valve between the condenser and air pump ; M the air pump, and 

 Q the discharge valve of the air pump, through which the air and hot water are 

 forced into the hot well K, from whence a part is raised by a small force pump to 

 the boiler feed head, and the rest runs off by a waste pipe. H is the blow valve to 

 the condenser, (art. 566.) The condenser and air pump are placed in a cistern, 

 which is constantly supplied with cold water by a pipe N. 



The jet should be made through a rose on the end of the pipe ; for, to produce 

 speedy and perfect condensation, the cold fluid should present the greatest possible 

 surface to the steam it is to condense, (see art. 280.) ; and it should be impelled 

 into the condenser with greater force than the ordinary head in the cistern 

 admits of. 



In large engines the connecting eduction pipe E, Fig. 1. may be on the outside 

 of the steam pipe S, and the parts of the slide connected only by a rod, as 

 mentioned in art. 447. 



