AnriFicrAL HEAT.] PKACTICE OF HORTICULTURE. [autificial iilvt. 



early and lato hour of the day." By this 

 imule of reasoiiiiif?, 8u^'<;estt'd by close obser- 

 vation, ho was k-d to adopt tlie ridgo-aud- 

 furrow priiu'iple for glass roofs*, which phjccs 



gen and carbon — all of which ore extremely 



injurious, not only to vegctablp, but to animal 

 life— it need excite no Burpritio that tlio pre- 

 ference has been given to steam over smoke, 



the glass in such a position, that tlio rays of in the heating of the forcing-house. Besidcn, 

 liflht in the mornings and evenings enter the bricks usually employc"d in constructing 



the structure without " let or hirulrance," and 

 present themselves more perpendicularly to 

 the glass at those periods when they are least 

 powerful ; whereas, at mid-day, when they arc 

 most powerful, they present themselves more 

 obliquely to it. 



APPLICATION OF ARTIFICIAL HEAT. 

 Hot or forcing-houses are .'loated by dif- 

 ferent means, and in various ways. The 

 means are hy JIiics and ivpcs ; and the ways 

 are in allowing the former to convey both 

 emoke and air through the building ; and the 

 latter to conduct steam or hot water in any 

 given direction. The other means are by 

 constructing the forcing-house in such a man- 

 ner as will enable the calorific action of the 

 Bun's rays to be increased ; and, occasionally, 

 by the heat wliich is produced by the process 

 of fermentation of vegetable substances : this 

 mode, however, is rapidly disappearing from 

 amongst us. The smoke-flue is now pretty 

 generally abandoned for the hot-water pipe, 

 which possesses many advantages over the 

 former. In the first, it is more lasting ; in 

 the second, it requires much less space ; in 

 the third, it admits of being placed in situa- 

 tions where the flue could not be placed; in 

 the fourth, it yields a more uniform heat ; in 

 the fifth, it can rarely be over-heated — a 

 great matter in a forcing-house ; in the sixth, 

 it is much more cleanly and elegant ; and, in 

 the seventh, it seldom gets into such a state 

 of disrepair as to require mending. On the 

 other hand, the flue is liable to burst by ex- 

 plosion from the ignition of the inflammable 

 gases generated within. This, of itself, is con- 

 demnatory to the flue ; and although the pipe is 

 more costly than the flue at its first erection, it 

 has usually been found the cheapest in the end. 

 It must be remembered that noxious gases 

 cannot be prevented from entering the struc- 

 ture, be the flue ever so well built; and when 

 it is considered that these gases consist of 

 sulphurated, phosphorated, and carburated 

 hydrogen, besides various comparts of uitro- 



tho flues, have, from the softneas of their 

 texture, the power of withdrawing from the 

 air of the house much of the moisture ne- 

 cessary for the health of the plants— a power 

 which the hot-water pipe, being unabsorbent, 

 does not possess. Upon this subject, the 

 Book of the Garden thus delivers its opinion 

 — •* Heating by hot water is, undoubtedly, the 

 most wholesome form yet adopted ; and, in its 

 various modifications, it may be applied to all 

 kinds of structures. The temperature it 

 produces is uniform and moderate when 

 compared with hot-air stoves, flues, or steam. 

 There arc a 'icw cases, however, which should 

 be noticed, where heating by hot water would 

 be attended with more expense than is ne- 

 cessary; and these are small green-houses and 

 nurserymen's plant-liouses, where only half- 

 hardy plants are kept, and where a well-con- 

 structed flue can be introduced without occu- 

 pying much space. These only require heat 

 suflicient to exclude frost; and they miglit be 

 heated by an Arnott's, White's, or other 

 stove, placed outside the building. In ordinary 

 winters, it might not be necessary to use the 

 stove above a dozen times ; and as frost, in 

 general, sets in pretty suddenly, these houses 

 would, by such means, be heated in less time 

 than by a hot-water boiler and pipe." 



The length into which a complete considera- 

 tion of this subject alone would lead us, 

 would occupy more than the space allotted to 

 us for the treatment of horticulture in this 

 work : we must, therefore, content ourselves by 

 referring the reader to the numerous systems 

 which he will find explained, and illustrated 

 by diagrams, in the Book of the Garden, by 

 Mr. Charles Mackintosh. After all that has 

 been said, written, and practically carried out 

 in this matter, it would appear that we have 

 still to be supplied with a proper heating 

 apparatus for the forcing-house. In an excel- 

 lent paper read by John Rogers, Esq., before 

 the Horticultural Society of London, we find 

 him declaring this fact. After alluding to 

 the many and various modes which have been 



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