SECT, vin.] MANAGEMENT OF THE STEAM ENGINE. 273 



valve, and afterwards the air. When all the air except that mixed with the steam 

 is driven out, which will be known by the sharp cracking noise at the blow valve, 

 this noise must be allowed to continue till it be supposed that there has been time 

 for at least as much steam as fills the engine to run through. Then shut off the 

 steam except to the upper side of the piston, and open the injection cock ; if motion 

 does not commence, the injection cock must be shut, and the blowing through of 

 steam repeated. If the engine have a steam case or jacket, that case must be 

 cleared of air and water, and filled with steam before the operation of blowing 

 through be commenced. 



The noncondensing species of engines require nothing more than to be heated 

 and freed from water, and atmospheric engines condensing in the cylinder to 

 be freed of air. 



567. OF THE MANAGEMENT OF THE FIRE. The chief thing is to obtain as 

 equable a supply of steam as possible ; and the object of the attendant must be to 

 render it so with the least occasion for opening the fire door. He must endeavour 

 to preserve a clear free burning fire, which cannot be done if it be allowed to 

 become foul by clinkers accumulating. Every coal which will not pass a ring of 

 about two inches and a half diameter should be broken ; and either feed frequently, 

 thinly, and equally over the surface of the fire, or adopt the method pointed out in 

 art. 249 ; but in important works Brunton's method should be applied (art. 250). 



568. Great care should be taken to keep the engine and boiler clean and 

 in good order, and for this purpose frequent and steady attention is more effectual 

 than twice the quantity of irregular labour. In work of this kind that which is 

 done well is twice done ; and the most furious zeal is vastly inferior to steady 

 attention, for the one destroys the objects of its care, the other preserves them. 



The best kinds of oil and tallow should be used : for piston grease, tallow is most 

 esteemed ; and when cylinders are new, a small addition of very soft black lead in 

 fine powder improves the effect of the tallow. Oil appears to be improved by the 

 addition of a small quantity of wax. 



2 M 



