THE BOILER.] 



PEACTICE OF HOETICULTURE. 



[heating. 



adopted for heating forcing-houses, and ac- 

 knowledging the decided superiority of the hot- 

 water system over all other methods, he states 

 that the saving of fuel is equal to 25 per cent, 

 in well-arranged hot-water apparatuses, over 

 flues, however well arranged or well managed 

 they may be. He, however, at the same time, 

 observes that many of the modes, even at pre- 

 sent in use, are so defective, that they actually 

 consume a greater amount of fuel than ordi- 

 nary furnaces : he then adds that " this remark 

 applies not merely to the earlier apparatus, 

 when the power was inadequate to the work 

 required, but even to the best-constructed 

 modern ones; and the waste of fuel arises 

 from a misunderstanding of the nature of a 

 hot-water apparatus, and from an attempt to 

 make it do that which, if it be properly con- 

 structed, it is impossible that it should do." 



CONSTRUCTION OF THE BOILER. 



Almost every variety of form has been sug- 

 gested, and even practically carried out, in 

 the construction of the boiler designed to heat 

 water for the forcing-house. As a matter of 

 course, many of these are of no value what- 

 ever; but in the Gardener's Magazine we find 

 the rationale of the process of heating the 

 conical boiler, invented by Mr. Rogers, of 

 Sevenoaks, Kent, thus given : — " As fuel 

 cannot be consumed without air, if a furnace 

 be constructed of considerable depth, and filled 

 with fuel, and air be admitted only at the 

 bottom, that fuel alone is consumed which lies 

 immediately on the bars, and first receives the 

 draught of air. The fuel above, provided it 

 transmits the air, becomes red-hot, or nearly 

 so ; but does not consume until that below it 

 is destroyed. In this manner, one of these 

 conical furnaces being lighted and filled with 

 fuel, that portion in the upper part of the 

 furnace which cannot burn, absorbs the heat 

 ot the burning fuel below, and radiates or 

 transmits it to the water on every side. So 

 perfect is this absorption of heat, that for 

 several hours after the furnace has been filled 

 up with cinders, though there may be a fierce 

 fire below, little or no heat escapes up the 

 chimney— the whole being taken up by the 

 surrounding water. The economy, tlierefore, 

 of fuel in such an apparatus is very great. 

 It ia evident that excess of draught must be 

 9GG 



carefully guarded against, so much only being 

 allowed as will consume the fuel steadily ; 

 but this is easily learned by experience. The 

 necessity, also, of keeping the aperture in 

 front close, so that air enters the furnace 

 only through the ash-pit, is, hence, evident. 

 The water is (then) in close and immediate 

 contact with the red-hot fuel on all sides, no 

 black, smoking coals intervening, as in most 

 kinds of boilers ; hence the great power in 

 proportion to size." In commenting upon 

 these boilers, another writer says, that the 

 economy in fuel is not their chief advantage ; 

 their great recommendation being a long and 

 steady heat. When properly managed, this 

 heat may be relied upon from fifteen to 

 twenty consecutive hours. Tbey have been 

 successfully applied to all kinds of hot-houses ; 

 but for pits they are eminently useful, from 

 the limited space they occupy. "When fired 

 with coke, gas-cinders, or anthracite, they 

 give off very little smoke. 



DIFFERENT MODES OF HEATING. 



An ingenious method of heating has been 

 exhibited by Mr. Fowler, in a tract written 

 on an instrument which he terms the ther- 

 mosyphon. By this contrivance, he shows 

 how walls, as well as glass-houses, may be 

 heated. He says, that any one may prove 

 that hot water will circulate in a syphon, by 

 taking a piece of lead pipe, say of half an inch 

 in bore, and four or five feet long, bending it 

 like a syphon ; but one leg a good deal more 

 bent than the other, in order to give the 

 descending water time and space for giving 

 out its heat ; and then filling this tube with 

 water, and placing one hand on each end to 

 retain it full, immerse the extremities in a pot 

 of water over a fire. Supposing the water of 

 a uniform temperature in both legs of the 

 syphon, no circulation would take place ; but 

 supposing it to cool sooner in the long leg 

 than in the short one, then the equilibrium 

 would be destroyed, and the water in the long 

 leg would descend and draw up water through 

 the short leg. This circulation would continue 

 as long as the water was preserved at a tem- 

 perature above that of the surrounding atmo- 

 sphere. 



Another invention is Mr. Kewley's adapta- 

 tion of the syphon to heating purposes. 



