208 



GREENHOUSES 



lar or water-tube boilers are almost always 

 used. 



Styles of Cast-Iron Boilers. There are 

 three general types or styles of cast-iron 

 boilers. The most popular is the "vertical" or 



"square"sectional boil- 

 er. The advantages 

 claimedfor these forms 

 of boilers are: (i) 

 They may be enlarged 

 by adding extra sec- 

 tions; (2) a break or 

 crack will usually be 

 confined to one sec- 

 tion; and (3) they may 

 be made in large sizes 

 because the individual 

 castings are compara- 

 tively small and light. 

 F . 107 c The sections are joined 



big. 107. A type of J 



'round" or "horizontal" together by accurate- 



sectional boiler -, 1 < 



ly ground push nip- 

 ples or by screw nipples. Probably 80 per 

 cent, of the cast-iron boilers now being 

 placed in greenhouses of moderate size are 

 of this general type- 



A second style of cast-iron boiler is 

 known as "horizontal" or "round" sectional 

 boiler. It gives good satisfaction in small 



