REMARKS ON ARTIFICIAL CLIMATE. 87 



for the former does not pretend to anticipate all the circumstances 

 accompanying the latter. The following statement may likewise 

 be of service in estimating the heating-surface required for diffe- 

 rent sizes of horticultural buildings. In stoves of considerable 

 dimensions containing from 50,000 to 60,000 cubic feet of air, 

 having a surface of glass (including rafters and sash-bars) in the 

 proportion of 1 square foot of glass to 10 cubic feet of air, the 

 proportion of 1 foot of 4-inch pipe to 5 ' 33 feet of glass will be 

 ample heating-surface to maintain a minimum temperature of 

 60"^ during severe weather. But in a house containing from 

 10,000 to 15,000 cubic feet of air, with a superficies of glass, 

 &c., in the proportion of 1 fo')t of glass to 6 "75 feet of air, the 

 proportion of 1 foot of pipe to 3 feet of glass will be required to 

 maintain a minimum temperature of 60° or 65^, provided cover- 

 ing be not used. In vineries and peach-houses the quantity of 

 heating-surface required will very much depend on circumstances 

 — as whether they are detached or connected in a range ; also 

 whether the crop is m anted early or late : but 1 foot of pipe to 

 4 feet of glass will be a fair average for vineries, and 1 foot of 

 pipe to 5 feet of glass for peach-houses. Conservatories and 

 green-houses, according to size and other circumstances, will re- 

 quire 1 foot of 4-inch pipe to 5 or 6 feet of glass. If flues 

 are preferred, I should consider 1 foot of an ordinary flue equal 

 to 2 feet of 4-inch pipe. In pits or small forcing-houses, where 

 covering can be easily applied at night, the proportion of 1 foot 

 of pipe to 4*5 feet of glass will maintain a minimum temperature 

 of 60^ 



Our fears of not being able to maintain sufficient heat and 

 moisture during winter often lead to errors of an opposite kind ; 

 for in the comparatively still atmosphere of a hot-house one of 

 the most powerful natural agents, both in drying and cooling, is 

 almost wholly excluded. It is probable that the rate of evapora- 

 tion during very strong wind is nearly double that in a hot-house. 

 In this country we seldom experience much iiiconveriience from 

 the drying effects of the weather during spring or summer, unless 

 accompanied by wind. I believe that very incorrect ideas are 

 often entertained concerning the drying effects of our heating 

 apparatus. In a house heated by iiot-water pipes, the moisture 

 of the air is not affected thereby ; the loss by condensation on the 

 glass in cold weather is, liowever, very considerable, and is in 

 direct proportion to tlie difference of temperature between the 

 internal and external air ; or, in other words, to the loss of heat 

 by radiation from the glass. The greatest degree of dryness will 

 perhaps occur when a nigiit of severe frost is succeeded by briglit 

 sunsiiine in the earlj'- part of the day ; but notwithstanding this, 

 if the glazing be complete, there will be no difficulty in supply- 



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