31. Another form of slides is shown in fig. 19. The steam 

 pipe proceeding from the boiler to the cylinder is represented at 



Fig. ID. 



A A, and it com- 

 municates with 

 passages s and s' 

 leading to the 

 top and bottom 

 of the cylinder. 

 These passages 

 are formed in 

 nozzles of iron or 

 other hard metal 

 cast upon the side 

 of the cylinder. 

 These nozzles 

 present a smooth 

 face outwards, 

 upon which the 

 slides B B', also 

 formed with 

 smooth faces, 

 play. The slides B B' are attached by knuckle-joints to rods 

 E E', which move through stuffing-boxes, and the connection of 

 these rods with the slides is such that the slides have play so as to 

 detach their surfaces easily from the smooth surfaces of the nozzles 

 when not pressed against these surfaces. The steam in the steam 

 pipe A A will press against the backs of the slides B B', and keep their 

 faces in steam-tight contact with the smooth surfaces of the nozzles. 

 These slides may be opened or closed by proper mechanism, at any 

 point of the stroke. When steam is to be admitted to the top of 

 the cylinder, the upper slide is raised and the passage s opened ; 

 and when it is to be admitted to the bottom of the cylinder, the 

 lower slide is raised and the passage s' opened : and its communi- 

 cation with the top or bottom of the cylinder is stopped by the 

 lowering of these slides respectively. On the other side of the 

 cylinder are provided two passages c c' leading to a pipe G, which 

 is continued to the condenser. On this pipe are cast nozzles of 

 iron or other metal presenting smooth faces towards the cylinder, 

 and having passages D D' communicating between the top and 

 bottom of the cylinder respectively and the pipe G G leading to 

 the condenser. Two slides b 6', having smooth faces turned from 

 the cylinder, and pressing upon the faces of the nozzles D D', are 

 governed by rods playing through stuffing-boxes, in the same 

 manner as already described. The faces of these slides being 

 turned from the cylinder, the steam in the cylinder having free 



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