222 VARIOUS METHODS OF HEATING DESCRIBED IN DETAIL. 



atmosphere. Plants watered with a weak solution of the salts 

 of ammonia (smelling salts) will, in a few days, show their 

 invigorating effects ; and plants grown in a hot-house, with 

 the atmosphere impregnated with ammonia, will exhibit, in 

 a manner equally as striking, its beneficial influence. Every 

 gardener is aware that plants, growing in frames or pits 

 heated with fermenting manufe, will, under ordinary circum- 

 stances, evince a much greater degree of luxuriance than in 

 any other situation. In fact, dung-beds are considered an an- 

 tidote for nearly every disease that plants are heir to, and not 

 without a well-grounded knowledge of their effects ; and 

 hence, when a gardener wishes to invigorate sickly plants, he 

 straightway plunges them into a hot-bed, and if there be any 

 vitality left in the plant, it seldom fails in pushing out vigorous- 

 ly. Now nothing is more obvious than the fact that neither the 

 heat, nor the moisture alone, produced this result ; for if the 

 plant had been plunged in a hot-bed warmed with the combus- 

 tion of fuel, in nine cases out of ten the result would have been 

 the very reverse. In fact, it is found, by long experience, that 

 neither heat nor moisture alone will compensate for the removal 

 of a sickly plant from the congenial warmth of a well-prepared 

 dung-bed. Now, the question which presents itself for solution, 

 in regard to this mode of heating, is, What is the cause of this 

 difference, and how can it be otherwise produced ? If we con- 

 sider the effects due to the gases already mentioned, to be fully 

 established, we will find that the secret of all this lies in the 

 stimulating gases of the manure, which constantly surround the 

 plants when exposed to the mild heat of a dung-bed. The old, 

 and now almost obsolete, plan of warming forcing-houses with 

 accumulated masses of fermenting manure, is well known ; and 

 the luxuriance of vines, forced by this method, is as well known 

 as the method itself. This luxuriance was produced by the 

 ammoniacal and other gases evolved during the process of fer- 

 mentation ; and though this method of forcing has been entirely 

 laid aside, on account of its unsightly appearance, and the incon- 

 venience of keeping up a constant supply of well-prepared ma- 

 nure, still the merits it possessed, by its ammoniacal properties, 

 have not yet been secured in any other mode of heating. 



