Hot-house Flues. By Alexander Seton, Esq. 239 



the furnace, mixes with the atmosphere of the house in dif- 

 ferent parts, and thereby produces an equality of tempera- 

 ture which could not otherwise be obtained. Whereas, with 

 the use of a single flue, even of brick or stone, the heat 

 which emanated by radiance is so powerful near the fur- 

 nace, that it is often injurious to the plants in that situation, 

 while in the more remote parts of the house it is so far ex- 

 pended as not to be sufficient for their wants. This circum- 

 stance precludes the use of iron for a single flue, but the 

 caseing prevents all inconvenience of that nature ; and the 

 iron, from its superior conducting power, is the means of 

 saving a great portion of the heat, which would, if brick or 

 stone were used, escape with the smoke by the chimney. 

 Another advantage is derived from the iron flue by means of 

 the closeness of its substance, as it entirely precludes the 

 escape of smoke and carbonic acid, and hydrogen gas, 

 which always takes place more or less, however impercepti- 

 bly, through the pores of the brick and mortar; and which I 

 believe to be the chief cause of the inferiority commonly ob- 

 served in the effects of fire flues on the health of plants, 

 when compared to those of steam pipes ; for whatever might 

 be the effects of any direct application of steam, we cannot 

 easily conceive that it will, when confined within an imper- 

 meable pipe, operate in any other way than by communica- 

 ting the heat uncontaminated by noxious exhalations. 



Some of the covering stones of Mr. Walker's caseing are 

 hollowed, to receive water for supplying steam occasionally, 

 when wanted in the house. This is often very useful; but 

 it appears to me that it may be done with more effect by 

 adapting a vessel to the iron flue itself, near the furnace, and 



