206 



GREENHOUSES 



use of the poorer grades of coal. But they do 

 sometimes crack, and they have a disgusting 

 way of doing it at the most inopportune 

 moment. 



ri 



Fig. 105. Side view of "square" sectional boiler 

 showing fire travel 



Where fuel is cheap and abundant, and 

 especially in small ranges, or where the boiler 

 is in a damp basement and likely to be neg- 

 lected during the summer, cast-iron boilers 

 are likely to give better satisfaction than 

 wrought-iron. In large establishments of 

 100,000 feet or over, large wrought-iron tubu- 



