86 RKMAUKS ON ABTIFICIAI. CLIMATE. 



diffusion of both. To supjjly an equal amount of these stimulants 

 in our nuirky climate would be erroneous in principle and inju- 

 rious to vegetation, Tiie last remark applies witii equal force to 

 night temperatures. 



Among the various agents employed in warming horticultural 

 buildings hot water is at present tliat most generally adopted. 

 Heating by flues answers for certain pur])oses — as for vineries, 

 greenhouses, &c. The Polmaise plan, which in particular cases 

 1 have found to be simple and efficient, is by far the most inex- 

 pensive to erect ; but under present arrangements it is difficidt to 

 apply it successfully to large houses. Price's ingenious plan of 

 heating, although it does not differ materially from other methods 

 of warming by hot water, in causing the air to carry the heat into 

 the building, has in some degree anticipated part of the Polmaise 

 plan : I, however, find this method very expensive with regard to 

 fuel. 



In the choice of boilers I imagine that we are often more nice 

 than wise. The saddle-shaped boiler of wrought iron, and the 

 cast iron boilers of various sizes, called Healy's, Cottam's, Kogers', 

 &c., have been tried here, and from experience I find that the 

 setting is of far more consequence than shape. Mr. Ainger, in 

 the ' Gardener's Chronicle' for 1841, clearly explained tlie prin- 

 ciples of setting boilers for horticultural purposes ; and Messrs. 

 Burbidge and Healy have subsequently adopted his plan, with 

 improvements. Their boiler I consider to be the best. 



Another important matter in warming is that the pipes shall 

 be so arranged as to give out heat rapidly. The amount of pipe 

 required, and the expense of heating any building, will very much 

 depend upon how far this is attended to. In some cases nearly 

 the whole of the heating surface is buried in underground chan- 

 nels or drains, sufficient heat being expected to rise through a few 

 openings in the pathway. It is clear that if tiie required amount 

 can be obtained at all under such conditions, it must be at an 

 enormous first cost, and an extravagant waste of fuel. The 

 question arises, why should a thing so essential to a horticultural 

 building be concealed as unsightly ? If the usual form of hot 

 water pipe is not ornamental it can be improved, and the pipes 

 may be so arranged as not to offend the eye of taste. 



Mr. Hood, in his valuable work on AVarming Buildings by Hot 

 AVater, gives a rule, and also a table, whereby we may ascertain 

 the required amount of pipe to heat a hothouse of given dimen- 

 sions any number of degrees ; and states that the quantities found 

 will be sufficient for a given superficies of glass, whatever the 

 size of the building may be. His rule may be safely relied on ; 

 although in this, as in other things, I find, as might be expected, 

 that differences occasionally occur between theory and practice; 



