CHAPTER VI. 

 THE BOILER 



A steam boiler is an apparatus in which heat is 

 transferred from burning fuel to water; where the 

 energy of the vibrating molecules of the burning fuel 

 is transferred to the molecules of the water, until the 

 motion of the latter becomes so violent as to cause 

 the mass or volume of steam to expand with a force 

 which can be readily harnessed for use. 



A boiler consists of the fire-box, in which the 

 combustion takes place, the water space, in which the 

 water is heated through contact with a heating sur- 

 face which surrounds the fire-box, passages to conduct 

 away the smoke and other products of combustion, 

 and various accessories to furnish water and regulate 

 the heat, etc. We have seen what a little loss of heat 

 means in the way of loss of energy, or power to do 

 work, and therefore the fire-box should be constructed 

 to direct as much of the heat of the flames and 

 burning gases to the surface against which the water 

 lies as possible; there should be no "dead" corners 

 where there is a loss of heat, and the smoke passages 

 should be so disposed as to utilize the heat from the 

 escaping gases. 



Boilers for traction engines may be roughly 

 divided into three classes: The locomotive boiler, 

 the return flue boiler, and the vertical or upright 



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