HEATING.] 



PRACTICE OP nORTICULTUEB. 



[iNBTttUMBNTS. 



Mr. Perkins constructed an apparatus con- 

 sisting of BUiall tubes, bernietically sealoci, in 

 which water circulated at a tennierature vary- 

 ing from .'^OO^ to •100'' Fahrenheit. This in- 

 vention, however, ia uusiiitablo for horticul- 

 tural purposes. 



Be.-*ides these, there is a mode of heating, 

 applied by Mr. Ivendlc, of Dynioutli, in wliich 

 tanks, in place of gutters or pipes, are em- 

 ployed, and which is designed to be adapted 

 to the purposes of both surface and bottom 

 heating. These tanks are built of brick or 

 stone, or made of cast-iron or wood. AVlien 

 made of wood, the planks require to be good 

 and sound, not less than a couple of inches 

 thick, well jointed ; and they are usually 

 covered with slates. If they are built of brick 

 or stone, the inside should be clothed with a 

 thick coating of Soman cement ; and their 

 covers should consist of slate, stone, or brick 

 pavement. The cast-iron tanks have covers 

 of the same materials. In describing this 

 mode of heating, a writer observes, that 

 " when only one tank is fitted up in a house or 

 pit, a division is made along the centre, 

 leaving an opening at the end furthest from 

 the boiler for the water to flow through ; the 

 hot water, or flow-pipe from the boiler, being 

 fixed to the end of the tank on one side of 

 the division ; and the cold water, or return 

 pipe to the boiler, being fixed to the end on 

 the opposite end of the division. When two 

 tanks are used, they are joined to the flow and 

 return 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 

 pipe." It would appear that the advantage 

 to be gained by this plan of heating, consists 

 in its adaptation to the production of bottom 

 heat. It is necessary, however, that pro- 

 vision should be made for preventing no more 

 of the steam or vapour rising from the hot 

 water (into the house) than is required. If 

 this precaution be not adopted, there will be 

 too much damp, in the winter season, for the 

 proper growth or preservation of the plants. 



In closing this important branch of our sub- 

 ject, it should be remarked that, in the 

 management of artificial heat, it is necessary 

 to exercise a considerable degree of care. All 

 the operations of nature being in opposition 



to those of artificial force, and being gradual, 

 tho best plan is to follow theni. Tlie skil- 

 ful horticulturist will, connequently, apply 

 his heat, ut lir.st, very gradually. Ho will, 

 for several weeks, slowly increase it by de- 

 grees ; and, ospeciully, ho will watch tliat 

 no sudden decrease of warmth occurs, as 

 nothing more certaiidy insures buccchh, tiiaa 

 that tho course of vegetation bo continued unin- 

 terruptedly through foliation, inflorescence, 

 and I'ructification. Ho will make tho tem- 

 perature increase by day, and decrease by 

 night ; to rise in summer, and to fall in 

 winter. In short, the operations of tho sun 

 shall bo his guide : by its natural and vary- 

 ing influence ho shall be ruled. 



SCIENTIFIC INSTRUMENTS. 



Tho scientific instruments absolutely ne- 

 cessary to the horticulturist, are a Fahrenheit 

 thermometer, which is not only an indispen- 

 sability in the forcing-house, but is required 

 in almost every department of his professional 

 practice. Six's registering thermometer ia 

 also a convenient instrument for ascertaining 

 the extremes of the temperatures of night and 

 day. Besides the thermometer, the hygro- 

 meter is very necessary to the hot-house, as it 

 measures the quality of elastic vapour in the 

 atmosphere ; and thus enables us to ascertain 

 the degrees of its humidity. In the Theory of 

 Horticulture, it is observed, that " skilful 

 balancing of temperature and moisture in the 

 air, and a just adaptation of them to the 

 various seasons of growth, constitute the most 

 complicated and diflicult part of a gardener's 

 art. An excess of dampness is indispensable 

 to plants in a state of rapid growth, partly 

 because it prevents the action of perspiration 

 from becoming too violent, and partly because, 

 under such circumstances, a considerable 

 quantity of aqueous food is absorbed from 

 the atmosphere, in addition to that obtained 

 by the roots. But it is essential to observe, 

 that when not in a state of rapid growth, a 

 largo amount of moisture in the air will be 

 prejudicial rather than advantageous to a 

 plant ; and if the temperature is, at the same 

 time, high, excitability will remain in a state 

 of continued action, and that rest which is 

 necessary will be withheld; the result of 



967 



