THE BOILER. 87 



on the pressure screw. To regulate the opening and closing 

 action of the valve, take the pointed end of a file and apply 

 it to the teeth of the regulator. If the valve closes with too 

 much loss of boiler pressure, move the regulator to the 

 right. This can be done when the valve is at the point of 

 blowing off. 



The Blower. The blower consists simply of a pipe 

 leading from the boiler to a nozzle in the smoke-stack. In 

 the pipe is a valve for shutting off the steam. On traction 

 engines, a rod is fitted to this valve, allowing it to be oper- 

 ated from the platform. The blower is intended for use 

 only in raising steam, when the engine is not running. When 

 the engine is running, its exhaust is discharged into the 

 smoke-stack, creating what is known as "forced" draft, as 

 distinguished from "natural" draft, which is due only to 

 the height of the chimney. When an engine has been 

 running and is temporarily shut down the blower should 

 not be used unless the entire grate surface is covered with 

 burning fuel. If. the blower be used soon after shutting 

 down and the grates are not entirely covered with burning 

 fuel, cold air will pass through the dead places in the grates 

 direct to the tubes, cooling them suddenly and rendering 

 them liable to leak. 



Foaming. When a boiler is "foaming," the water in the 

 glass appears roily and the level changes rapidly, the glass 

 appearing full one moment and nearly empty the next. Dirty 

 water is usually the cause of foaming, alkali, or soap in any 

 quantities being especially bad.' No one should be allowed 



