228 



HEATING AS APPLIED IN HORTICULTURE. 



the heating of the bark bed by hot air 

 being admitted under it, Mr Ayres found, 

 instead of a uniform heat, that at " one 

 end the temperature was little more than 

 70°, while, where the heat entered, the 

 bottoms of the pits were so hot, I could 

 scarcely bear my hands upon them. The 

 grand fundamental error of the system is 

 that of radiating heat at a high tempera- 

 ture ; and it may be laid down as an in- 

 controvertible and established fact, that 

 no system which does that, whether it be 

 hot air or hot water, is capable of generat- 

 ing a fine, genial, and healthy atmosphere 

 either for plants or man. 1 ' 



Regarding the unwholesomeness of at- 

 mospheres heated by iron hot-air stoves, 

 Dr Ure remarks — " When coke is burned 

 very slowly in an iron box, the carbonic 

 acid gas which is generated, being half as 

 heavy again as the atmospherical air, can- 

 not ascend in the chimney at the tempe- 

 rature of 300°, but regurgitates into the 

 apartment through every pore in the 

 stove, and poisons the atmosphere. I have 

 recently," says Dr Ure, " performed some 

 careful experiments upon this subject, 

 and find that, when the fuel is burning 

 so slowly in the stove as not to heat the 

 iron surface above the 250th or 300th 

 degree of Fahr., there is a constant 

 deflux of carbonic-acid gas from the ash- 

 pit into the apartment. This noxious 

 emanation is most easily evinced by ap- 

 plying the beak of a mattrass, containing 

 a little Goulard's extract, (solution of 

 subacetate of lead,) to a round hole in 

 the door of the ash-pit of a stove in this 

 languid state of combustion. In a few 

 seconds the liquid will become milky by 

 the reception of carbonic-acid gas." — Dr 

 Uke's Diet, of Arts, &c. 



The same authority also observes, as 

 to the unwholesomeness of hot-air stoves, 

 particularly such as are wholly or in part 

 constructed of iron, that "as cast-iron 

 always contains, besides the metal itself, 

 more or less carbon, sulphur, phosphorus, 

 or even arsenic, it is possible that the 

 smell of air passed over it in an incan- 

 descent state, may be owing to some of 

 these impregnations ; for a quantity of 

 noxious effluvia, imperceptibly small, is 

 capable of affecting not only the olfactory 

 nerves, but the pulmonary organs. He 

 also states a case at great length of the 

 dangerous effects of heating air by mak- 



ing it pass over highly-heated iron plates, 

 as having occurred to the persons em- 

 ployed in the long-room in the custom- 

 house of London, nearly all of whom 

 were attacked with severe illness." Not 

 only is the air rendered unhealthy by 

 being brought into contact with heated 

 iron plates, but even were it otherwise, 

 the equal diffusion of air, and still more, 

 conducting it to a distance from the fire, 

 appear to be so little under the control 

 of man, that we are really surprised to 

 see so many otherwise intelligent men, 

 and men for whose general opinions 

 we have so much respect, advocating a 

 system so void of utility, and pregnant 

 with evil. Steam and hot water may be, 

 and have been, carried for hundreds, nay, 

 thousands of feet from the boiler; hot 

 air, even at Polmaise, scarcely thirty. 



§ 6. — HEATING BY STEAM. 



Heating by steam, so far as hothouses, 

 &c, are concerned, is now so completely 

 superseded by hot water that our obser- 

 vations on it need only be brief. 



It appears pretty certain that the cele- 

 brated lawyer, Sir Hugh Piatt, was the 

 first to suggest steam as a heating me- 

 dium for horticultural purposes. In his 

 curious work, " The Garden of Eden," p. 

 19, an account of his method is given. 

 Colonel William Cook, in 1745, improved 

 on Sir H. Piatt's plan ; and in 1755, we 

 find that it was suggested as a method for 

 forcing fruits. The celebrated Watt re- 

 duced these hints to practice; and the 

 philosophy of the method was first ex- 

 plained by the no less eminent Leslie. 

 In or about 1789, Mr Boulton heated a 

 room in his house by it, and soon after- 

 wards a bath also. 



The first successful application of steam 

 for heating a hothouse was made by 

 Wakefield of Liverpool, in 1788 ; and 

 patents were first granted to Hoyle of 

 Halifax, and soon afterwards to Green of 

 London. — Vide Rep. of Arts, vol. ii. p. 

 304, and vol. i. p. 304. The principle of 

 the former was to convey the condensed 

 steam back to the cistern that supplied 

 the boiler ; that of the latter consisted in 

 carrying a worm-pipe through the boiler 

 containing hot water or steam, with a 

 view to moderate the heat, and keep the 



