HoT WATER. 311 
of draught must be carefully guarded: against, so much 
only being allowed as will consume the fuel steadily, which 
is easily learned by experience. The necessity, also, of 
keeping the aperture in front close, so that air enters the 
furnace only through the ash-pit, is hence evident. The 
water (as may be observed in Fig. 31).is: in close’ and im- 
mediate contact with the red-hot fuel on all sides, no. black 
smoking coals intervening, as in most minds of sari 
hence the great power in proportion to size.’ pat petite 
Tke economy of fuel in these boilers is not their prin- 
cipal advantage; but their ‘great recommendation is a long- 
continued and steady heat. When properly managed, they 
Fig. 32, 
ii 
TET 
RA ALAMO 
Pauanui 
I 
I 
| 
| 
Eh 
3 
F| 
Et 
3 
€ 
3 
2 
may be depended on for preserving the heat for from fifteen 
to twenty hours. They have been successfully applied to 
all descriptions of hot-houses, but for pits they are emi- 
nently useful, from the small space they occupy; and when 
fired with coke, gas-cinders, or anthracite, they give off 
very little smoke. 
It is unnecessary to describe all the numerous modi ca 
6 
