196 



HEATING AS APPLIED IN HORTICULTURE. 



circulation from the tank, after with- 

 drawing the water in it, and using the 

 hot-water pipes alone. Mr Rendle's pro- 

 visions to remedy this defect are thus 

 described by him in "The Gardeners' 

 Chronicle," and the annexed woodcuts 

 also given, which exhibit part of the 

 ground-plan, fig. 252, and perspective 



Fig. 252. 



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1 



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b 





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view, fig. 253, of a propagating-house 

 in his highly respectable establishment. 



Fig. 253. 



" The water enters the tank at a, and, by 

 means of plugs or valves at the apertures 

 b, can be made to circulate round the 

 tanks and pipes, or be [ made to pass 

 through the tanks or pipes separately :" 

 c is the boiler ; d d the hot-water pipes, 

 irrespective of the tank. 



This is a very efficiently heated house, 

 and reflects great credit on Mr Rendle. 



Objections have been made, and ques- 

 tions put, as to whether the pipes used in 

 conjunction with the above plan should 

 not be kept exactly level with the tanks. 

 To this we answer, that the pipes may be 

 under or upon a level with the tank, in 

 ordinary cases ; or they may be elevated 

 considerably above it, by adopting the 

 siphon system. It is well, in our opinion, 



in all cases connected with hot-water 

 heating, where it can be done, to adopt 

 the level or horizontal mode of circula- 

 tion. It is the simplest, as well as equally 

 efficient with any other, therefore the 

 best ; and it should never be departed 

 from, unless where obstacles occur that 

 may render a deviation from it expedient. 

 To circulate water in pipes upon a higher 

 level than that of the tank, the flow-pipe 

 should be placed at least 2 inches higher 

 in the water than the return-pipe ; and at 

 the highest point to which the flow-pipe 

 is carried, let there be an air-cock or 

 means for attaching an air-pump, to draw 

 off the air that may accumulate in the 

 pipes. Tanks to which a siphon-pipe is 

 to be attached should have a depth of at 

 least 6 inches of water, the more com- 

 pletely to prevent the entrance of air into 

 the pipes. Or a hollow basin may be 

 formed in the tank a foot or more in 

 depth, into which the ends of the siphon- 

 pipes may dip ; and as that never can be 

 without water while any remains in the 

 tank, the exclusion of air from the pipes 

 may be safely calculated upon. 



Opinions are at variance in regard to 

 the proper depth of water in the tanks. 

 The shallower they are, we believe it is 

 admitted on all hands, the sooner they 

 will be heated ; and the deeper they are, 

 the longer time will be required. It has 

 also been disputed, whether the larger 

 or smaller quantity of water employed 

 requires most fuel. Mr Sherwood, an in- 

 telligent correspondent in "The Gardeners' 

 Chronicle," after expressing his doubts 

 that the saving of fire is attributable to 

 the use of a large body of water, observes 

 on this subject, "Whether the quantity of 

 water be large or small, it merely trans- 

 mits the heat given off in the combustion 

 of the fuel to the air of the house. As 

 the air is constantly being cooled, a con- 

 tinual demand of heat is made on the 

 radiating surface, to maintain the desired 

 degree of temperature. Now, through 

 whatever medium this heat maybe impart- 

 ed to the house, the quantity of fuel neces- 

 sary to produce it will always be pretty 

 much the same. If a large body of water 

 yields twice as much heat as a smaller 

 quantity, it is because it has first received 

 twice as much as the other. My opinion," 

 he continues "is, that the most econo- 

 mical qualities of a heating apparatus 



