SCIENCE OF THRESHING. 



105 



The vertical type comprises merely a vertical, 

 cylindrical shell with vertical flues and fire-box under 

 them. 



The main object in the distribution and arrange- 

 ment of the parts are twofold. First, direction of the 

 heat of the fuel against spaces or walls the other side 

 of which are in contact with the water, so that the 

 energy of the burning fuel may not be dissipated or 

 wasted on the outer air, or outer parts of the boiler. 

 Second, presenting as large a surface of water as 

 possible to the heated surfaces. The fire-box should 

 be arranged with proper grates and draft openings 

 to suit the fuel to be used and should be easily 

 cleaned. The water spaces should surround the fire- 

 box as completely as possible so as to present a large 

 heating surface and prevent its plates from over- 

 heating. The boiler should be cleaned regularly of 

 all mud and settlings left by boiling away the water. 

 When using ordinary well water, once a week is often 

 enough to clean out. In muddy or alkali water, the 

 boiler may require to be emptied oftener than once 

 a week. 



