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SECTION III. 



HEATING BY HOT WATER, HOT AIR, AND STEAM. 



1. THE practice of employing hot water, circulating through 

 metallic tubes, or wooden troughs, for diffusing artificial heat in 

 horticultural structures, though of recent origin, has now become 

 so general, that its merits are fully acknowledged as the best 

 method that has yet been invented, to effect the purpose with 

 efficiency and economy. Until the last few years, although 

 its powers and properties were fully known, it had been 

 chiefly confined to a few cases of experiment, rather than to any 

 general or useful purpose. 



The present day, however, has fully revealed its merits, and 

 shown the great, the unlimited, extent of its practical application 

 and general utility. When we see such an immense structure 

 as the great Palm house, lately erected at Kew Gardens, in 

 London, heated with hot water in preference to all other modes ; 

 when we see the lately applauded mode of heating by steam 

 abandoned; when we see the powerful, but unsuccessful, at- 

 tempt to establish a new system of heating by hot air, called 

 Polmaise, by some of the first horticulturists of England ; when 

 we see this system, notwithstanding its powerful supporters, 

 driven into obscurity, and all but annihilated, by the well-tried 

 superiority of hot water, which maintains its proud preeminence 

 over all other methods of heating, and has its superiority ac- 

 knowledged, even by its enemies. 



One of the greatest advantages which this mode of heating 

 possesses over all others, is, that a greater permanency of tem- 

 perature can be obtained by it, than by any other method. The 

 difference between an apparatus heated by hot water, and one 

 heated by steam, is not less remarkable, in this particular, than 

 in its superior economy of fuel. 

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