ON THE METHOD OF WARMING STOVES. 143 



for on any other principle, as I believe it has been satisfactorily ascer- 

 tained, that vegetable life does not destroy the vital properties of air 

 in the manner that animal life does : but that, although the air is much 

 altered by it at one period of the day, it is restored to its former state 

 in another, and on the whole no material change is permanently pro- 

 duced. Mr. Knight, the scientific president of the London Horticul- 

 tural Society, condemning the bark bed, except for the purpose of 

 striking young plants, has had a house constructed for the purpose of 

 growing stove plants without bottom heat, and from time to time has 

 given a detail of his proceedings and results. In one of his papers he 

 states, that the plants which stood on the hottest part of the flues, 

 immediately above where the fire entered, grew stronger and more 

 luxuriantly than the rest. This is exactly as might have been expected, 

 for the plants, standing above the source of the heat, would have the 

 benefit of first receiving the heated particles of air in their ascent, 

 and consequently would be in a situation more congenial to nature 

 than those in other parts of the stove where their leaves would be in a 

 warmer stratum of air than their stems and roots, though this was 

 also diminished as much as possible, by always keeping the plants in 

 contact with the glass, and was effected by placing the pots on pe- 

 destals of loose bricks. 



But in the construction of a house for this purpose, the circum- 

 stance that the heat under glass increases with the distance from 

 the ground should always be kept in view. Possibly if any method 

 could be found of agitating, or, as it were, mixing the inclosed air, it 

 might counteract this tendency to an undue accumulation of heat 

 above the plants. The flue probably had best be made to traverse 

 the house several times at a level below the pots, but on no account 

 must it be piled up against the back wall, which in all cases is 

 evidently an injudicious construction, throwing additional heat into a 

 part of the house, which without it has a tendency to exceed the rest 

 in temperature. 



May 13, 1840. 



