THE LOCOMOTIVE 



251 



the slide valve. These parts 

 are so adjusted that the slide 

 valve covers and uncovers the 

 openings at just the right time 

 to allow the steam to enter 

 each in turn. Two eccentrics 

 are provided for each valve, 

 one for the forward motion 

 when the locomotive is going 

 ahead, and another for the 

 backward motion when the 

 locomotive is going backward. 



The link. (See figure 92.) 

 One very important part of the 

 mechanism is the link, which 

 consists of a curved piece of 

 steel, the ends of which are 

 connected with the eccentric 

 rods. This serves two im- 

 portant uses, it enables the 

 engineer both to reverse the en- 

 gine and to control the amount 

 of steam that enters the 

 cylinder. When the engineer 

 wishes to reverse the engine, 

 he throws over a lever which 

 is connected with the link, 

 and this moves the slide 

 valve in such a way that its 

 position is quickly changed, 

 so that the piston is made 

 to move in the opposite di- 

 rection. 



Another purpose served by 

 the link is to enable the en- 



