BOILERS, FUELS AND FLUES 



209 



ranges but is not made in large sizes. In 

 a third style there are no sections, but the 

 boiler proper is cast in one piece. For this 

 reason its size is limited. It is also open 

 to the disadvantage that a crack will spoil 

 the whole boiler. It is little used at present. 



Fig. 108. Corrugated fire box -boiler. The boiler 

 proper is of a single casting 



Styles of Wrought-Iron Boilers. Most 

 wrought-iron boilers are either tubular or 

 water-tube in construction, though the tubes 

 or flues are sometimes connected with cast- 

 iron headers. A new type of wrought-iron 

 boiler is now being extensively advertised for 

 greenhouse heating. It is claimed for this 

 type that it steams more quickly than the 



