Il6 SCIENCE OF THRESHING. 



When the steam gauge registers fifteen or twenty 

 pounds, the blower may be opened, but this should be 

 done with caution, as the fierce heat resulting from 

 its use is very trying on the parts directly exposed to 

 the fire. The heat too will be unequally distributed 

 in different parts of the boiler and the result will be 

 unequal expansion and consequent leakage and weak- 

 ening of joints. The initial or first firing of the 

 boiler should be done with care, in order to bring all 

 the parts to as even a heat as possible. The average 

 sized traction boiler should be allowed from forty- 

 five minutes to an hour in which to come to a full 

 head of steam. 



Soot and scale are very poor conductors of heat, 

 and the fire walls and flues should be kept as free 

 from them as possible in order that they may have a 

 fair chance to transmit the heat as directly as possible 

 to the water. The losses consequent on leaving the 

 firewalls lined with dirt amount to a considerable, 

 from the extra amount of fuel required to generate 

 the heat. 



The boiler should not be blown off when hot, as the 

 sudden cooling is as bad as the sudden heating, while 

 any scale on the shell and flues hardens and bakes on 

 the walls, thereby being removed with difficulty. 



The boiler should be properly jacketed with a 

 covering of non-conducting material to prevent loss 

 of heat by radiation. 



Inasmuch as the traction engine uses all kinds of 

 water, some highly alkaline or soapy, thereby 

 foaming, and others highly acid, corroding the plates, 



