248 Polmaise Method of Heating 



edgment is itself an evidence that the system is fast sinking 

 in spite of its supporters ; and, indeed, this appears to be the 

 only vestige of merit that remains to reprieve it from oblivion, 

 to which it otherwise had long since been consigned. To 

 admit that it is useless for any other than pits, &c., is a tacit 

 admission that it is wrong in principle, for, if the principle 

 upon which an apparatus works be good, it will answer 

 equally well in houses of all sizes. Hot water pipes, for in- 

 stance, heat large houses as effectually and satisfactorily as 

 they do pits, because the principle is good, viz., rapid con- 

 duction and extensive radiation, in both of which Polmaise 

 is deficient. It is commonly the fate of erroneous positions, 

 that they are weakened by defence and obscured by explana- 

 tion, especially as in the present case, when its defenders 

 deviate from demonstrable evidence, and raise a mist where 

 there should be perspicuity. In the Gardener''s Chronicle, 

 Polmaise has repeatedly been extolled as the best of all 

 methods for heating hothouses, and, from the tone of its 

 editor and others, one would suppose that smoke-flues, hot 

 water pipes, and all other systems were soon to be numbered 

 among the things that were. Yet we find hothouses fitted 

 up with hot-water pipes almost under his immediate control, 

 showing at once an inconsistency and confutation of Polmaise 

 by its greatest advocate. 



I have said that Polmaise, or heating by hot air in any 

 form, cannot be proved, by demonstrable evidence, to be su- 

 perior to hot water, or even the common flue, for warming 

 small houses, and I am anxious to learn the various items of 

 its adaptability. We all know very well that small houses 

 are more easily heated than large ones, for the simple reason, 

 that the volume of air to be raised to a given temperature is 

 smaller, and the external surface of radiation less. The in- 

 ternal surfaces of radiation in small houses are generally 

 much larger, in proportion to the volume of air and external 

 surface, than in large houses. The radiating surface in small 

 houses is generally more than what is required, while the 

 radiating surface in a large house is, on many occasions, not 

 half sufficient for the work it has to perform. The power 



