Heating Apparatus 



writer has had some experience in these directions, but he would not 

 care to proclaim his work as being altogether a model of superb workman- 

 ship. At the same time it is useful for a grower, and especially one 

 with limited means, to be able, at a pinch, to build a greenhouse, or set or 

 repair a boiler. It sometimes happens, usually on a frosty night in the 

 depth of winter, that a boiler springs a leak, or a pipe crack.s or bursts in 

 some place. Under these conditions it is no use waiting for the expert to 

 arrive, while the crops are being frozen or scalded to death, and prompt 

 measures must be taken. The old boiler may have to be taken out at 



Fig. 178. The " Mona " Boiler 



once and replaced with a secondhand one on the premises, or a defective 

 section of piping must be replaced immediately with a sound one. It is 

 in special circumstances like these that a man who understands how to 

 set a boiler or replace a pipe is of the greatest value. There is nothing 

 lost therefore in acquiring a practical and theoretical knowledge of the 

 art of heating by boiler and pipes. 



Principles of Hot-water Circulation. Every grower should know 

 why the water from the boiler rises and flows upwards through the flow 

 pipes and comes back again to the boiler by the return pipes. It may be 

 possible to explain this by means of the accompanying diagram (flg. 179). 

 Let A represent a boiler with flow pipe at B, return pipe at C, and fire 

 at D. When heat is applied, some of the water in the boiler absorbs heat 

 and therefore expands and becomes lighter, and requires more space. 



