332 FORCING GARDEN. 



to the end, on the opposite side of the division. When 

 two tanks are used, they are joined to the flow and re- 

 turn pipes respectively, and united at the extreme ends. 

 In pits, the tanks may be carried round the sides and 

 ends of the pit, with -a division between the flow and 

 return pipes. 



The principal advantage of the application of this 

 mode of heating consists in the production of bottom 

 heat. Proper provision ought, however, to be made for 

 preventing more of the steam or vapor rising from the 

 hot water (into the house) than what is requisite ; for, 

 if this precaution be not adopted, there will be too much 

 damp in the winter season for the proper growth or pre- 

 servation of the plants.* 



To mention the rays of the sun amongst the sources of 

 artificial heat may excite a smile ; yet it happens that, 

 from the stagnation of air, the reflection of light from 

 walls, and other circumstances, they often produce a 

 very considerable proportion of the increased tempera- 

 ture of a hot-house. This species of heat, however, is 



■^ It will be seen that Mr. Rendle's mode of heating is merely 

 an extension of that of Mr. Corbett, described above ; and as some 

 interest was excited by Mr. Corbett^s claim to originality in his 

 mode of heating, it may be proper to state that his patent was seal- 

 ed in August, 1838, while the same mode, as described at page 362, 

 was in operation in the gardens at Hopetoun House in October, 

 1832, two years before the publication of this treatise in the Ency- 

 clopaedia Britannica. In the Gardener's Magazine for 1830, a de- 

 scription is given of a house fitted up in the nursery of Mr. Knight, 

 King's Koad, Chelsea, by Mr. George Jones, of Birmingham, with 

 cast iron troughs and movable covers, from which account Mr. 

 Smith believes it was that he made the application of the troughs 

 in the pits he designed, as described at page 3C3 of the present 

 treatise. 



