THE FEED WATER. 17 



of his most important duties. The glass can be cleaned at 

 any time by wiping the outside and blowing steam 

 through the inside. It is only necessary, in wiping, to see 

 that it is not scratched by sand or the like, for scratches are 

 likely to cause it to break. An old glass with a coating on 

 the inside that steam will not blow out, may be cleaned by 

 removing it from the connections and running a piece of 

 waste or cloth through it with a stick. Touching a glass on 

 the inside with a piece of metal of any kind is almost sure 

 to scratch it so that it will crack when the steam is turned on. 



Packing the Water-Glass. The best method of packing 

 the water glass is by means of the rubber gaskets made for 

 the purpose. These may be purchased for a few cents. 

 Candle wicking, hemp or asbestos is sometimes used, but 

 any of these packings is liable to become displaced and cause 

 trouble. The author has in mind a case in which a crown 

 sheet was badly burnt on account of the glass not showing 

 the true level of the water in the boiler, because the candle 

 wicking, with which it was packed, was forced, by the tight- 

 ening of the packing-nut, over the lower end of the glass, 

 practically shutting off the water. 



Broken Water-Glass. In case the water glass breaks 

 when the boiler is under pressure, shut both valves to stop 

 the escape of steam and water. The engine can be run by 

 gage-cocks until a new glass may be obtained. If a new 

 glass be at hand, it may be put in at once, but care should 

 be taken to heat it gradually, for if the steam be turned on 

 suddenly, it will break. 



