STEAM BOILERS 



319 



marine, portable, semi-portable, and stationary boilers, 

 according to use ; and according to form we have hori- 

 zontal and vertical boilers. Further, the horizontal class 

 may be subdivided into internally and externally fired, 

 shell, return-flue, fire-tube and water-tube boilers. For 



FIG. 214 WATER-TUBE VERTICAL BOILER 



rural use the marine type is very seldom used, and the 

 sectional only in rare cases. 



440. Vertical boilers. Boilers of this type (Fig. 212) 

 are not very economical. They require little floor space 

 and are easily installed. In construction they consist of 

 a vertical shell, in the lower end of which are the fire box 

 and ash pit ; extending up from the furnace and reaching 

 the top are the fire flues... 



