HEATING BY HOT-AIR STOVES. 



223 



p. 62, vol. ii. " Journal of the Horticultural 

 Society," — "My present tank, which is 

 5 feet long, by 3 feet 6 inches wide, and 

 4 inches deep," and placed over the hot- 

 plate of his stove, "will evaporate fifty 

 gallons per week. " But how much of this 

 vapour enters the hothouse he does not 

 say j nor could he suppose that any very 

 great proportion of it would do so, con- 

 sidering that his tank was placed over a 

 stoke-hole without the house, and that 

 aqueous vapour naturally ascends perpen- 

 dicularly upwards, and not horizontally, 

 as it would require to do, in order to gain 

 admission within the walls of his house. 

 How a healthy atmosphere is to be pro- 

 duced by these means, is, we confess, be- 

 yond our comprehension. Besides, fifty 

 gallons per week is no very abundant 

 supply of humidity to the atmosphere of 

 a house 28 feet by 17 in surface area, 

 and heated by a stove pre-eminently 

 adapted for a manufacturer's drying-house. 



As regards an "equal distribution of 

 heat entirely independent of external cir- 

 cumstances," this is still more extraordi- 

 nary, as it appears to us that "external 

 circumstances " have most essentially to 

 do with whatever distribution may take 

 place in the matter ; else why depend on 

 the external supplies of air admitted by 

 the openings c c c in the ground-plan, and 

 from no other source whatever ? 



That a pretty constant motion of at- 

 mosphere within the house will be pro- 

 duced so long as the stove is kept warm, 

 it is quite possible to believe ; because, 

 the air becoming highly rarefied over and 

 around the stove, in consequence of its 

 great heat, it naturally follows that the 

 heavier and cold air entering at the nu- 

 merous openings will rush in and be 

 diffused through the house, so long as 

 the air around the stove is kept warmer 

 than the external atmosphere without; 

 and this circulation will be increased as 

 the heat about the stove is augmented, 

 and vice versa. 



However sanguine Mr Meek may have 

 been as to the perfection of the Polmaise 

 stove, he was not entirely blind to its 

 imperfections. " Having noticed the ad- 

 vantages," he says, " of the Polmaise heat- 

 ing, I have no wish to conceal its dangers. 

 Man may take the principles of nature, 

 and when he reduces them to practice, he 

 finds that he has introduced some human 



imperfection ; and so it is with Polmaise. 

 A boiler may burst, or a pipe choke up 

 with a hot-water apparatus, and a gase- 

 ous exhalation may escape from the stove 

 of Polmaise. The compounds of sulphur 

 and oxygen appear, even when much di- 

 luted, most prejudicial to vegetable life, 

 and the effects of the bursting of a flue 

 are well known ; and this is the point of 

 danger. I prophesy," he says, " that no 

 winter, however severe, will affect the 

 operation of Polmaise. " But he at the 

 same time candidly says — "But all the 

 beauty of this principle of heating must 

 be sacrificed, unless we can secure the 

 chamber from gaseous exhalations. With 

 this view, let me urge upon all those who 

 may employ the Polmaise principle, to be 

 extremely particular in the manner in 

 which the stove is built. Let the outside 

 be parged ; let it be constructed of at 

 least 9-inch brickwork ; and if the iron 

 plate can be cast in one, with a project- 

 ing rebate on its under surface, and this 

 rebate dropped into a sand groove, fig. 

 301, it appears that all possibility of ex- 



Fig. 301. 



halation must be precluded. Indeed, if 

 even this were insufficient, it is hardly 

 probable that a sound principle of heat- 

 ing should be lost for want of some inge- 

 nious mechanical contrivance to prevent 

 exhalation." Why employ metallic plates 

 at all for covering, when fire-clay tiles, 

 either in one piece or in several, would 

 answer the purpose of heating, not only 

 much better, but without half of the dis- 

 advantages the present stove possesses 1 

 The annexed sections, figs. 302 and 



Fig. 302. 



303, exhibit a modification of the Pol- 

 maise stove proposed by Messrs Burbidge 



