190 GREENHOUSE CONSTRUCTION AND HEATING. 
lengths of piping, the great height of the larger sizes 
renders a deep stoke-hole necessary, while it is also not 
particularly economical in fuel, and in fact is almost out 
ale 
of date now. The ‘“ Excelsior” is another form of the 
same thing, but with straight or upright sides (not conical) ; 
this is made in wrought iron as well as in cast metal. 
Fig. 181. 
