The Garden Guide

Book: Gardening Tools, Equipment and Buildings
Chapter: Chapter 6: Structures used in Gardening

Drying effects of heated air in greenhouses

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2152. The drain of moisture by the escape of heated air is much greater than is generally imagined; but some idea of it may be formed from the following considerations. 'The capacity of air for moisture, that is to say, the quantity of water which a cubic foot of air will hold in invisible solution, depends upon its temperature, and increases with it in a rapid ratio. It is doubled between 44ᆭ and 66ᆭ. The consequence is, that every cubic foot of air which escapes at the latter temperature carries off with it twice as much moisture as it brought in. Where the difference of temperature is greater, the drain becomes greater also: air entering at 44ᆭ, and escaping at 80ᆭ, carries off three times as much as it brought; escaping at 90ᆭ, four times.' (Rogers in Gard. Mag., vol. xvi. p. 282.)