272 



VENTILATION. 



houses began to be constructed of sepa- 

 rate sashes and rafters, means were con- 

 trived by which ventilation was effected, 

 chiefly by mounting the sashes on rollers, 

 so that they could readily slide over each 

 other. On the Continent, where the 

 fixed roofs were, and still are, common, 

 portions of them near the top are made 

 to open, by being hinged to the wall- 

 plate, and propped up by a long wooden 

 handle, reaching nearly to the ground, 

 inside of the house. We have seen the 

 same principle adopted even in this 

 country, and in very modern houses, 

 only substituting an iron rod for a thick 

 wooden pole. 



Ventilation, for a long time after the 

 invention of hothouses, was considered 

 necessary only with reference to prevent- 

 ing the atmosphere of the structure from 

 becoming too much heated. Still, too 

 often it is the temperature, and not the 

 actual change of pure air for that which 

 has become vitiated and impure, that is 

 thought of. 



New and more rational views have 

 arisen, and improvements followed. Still 

 we must confess much yet remains to be 

 done; but as the natural properties of 

 air are now better understood, we have 

 hopes that, ere long, ventilation may be 

 effected upon true and correct principles. 



In a leading article, some time ago, in 

 " The Gardeners' Chronicle," written, we 

 presume, by the talented editor, Dr 

 Lindley, we have the following piquant 

 observations : " When a man builds a 

 forcing-house, he settles carefully the 

 slope of the roof, the nature and direction 

 of the heating apparatus, the material 

 for his shelves and floors, the quality of 

 his glass, the size of the squares, and the 

 depth of their laps. Whether the door 

 shall be at the end or side, and the 

 whereabouts of the stoke-hole, are other 

 points of grave deliberation. How, then, 

 are we to account for the almost univer- 

 sal neglect of the most important part of 

 all — the Ventilation 1 



" But no : we wrong the builders of 

 forcing-houses; — they do not neglect ven- 

 tilation ; on the contrary, they provide 

 for it copiously. They make the roof- 

 sashes slide, and the side- windows unfold, 

 and the door-way alone administers 

 no inconsiderable doses of wind. In 

 fact, the ventilation— if by that term is 



meant the letting in of wind — is in no 

 ways deficient. But unfortunately this 

 is not precisely what plants require. 

 They want in-draughts neither of hot 

 dry air in the dog-days, nor of ice-cold 

 breezes in the winter. Both hot and cold 

 air act like water ; the one scalds, the 

 other freezes. It is because of the danger 

 of such ventilation as this that gardeners 

 have concluded that a close moist atmos- 

 phere is indispensable to vines when in 

 flower — a singular mistake, which the 

 author of this article has disposed of 

 some years ago. 



" If we did not hate new words," says 

 the same high authority, " we should be 

 half inclined to expunge ventilation from 

 the language of gardening, and to substi- 

 tute zephyration, or some such gentle 

 epithet. We shall, however, content 

 ourselves with distinguishing ventilation 

 from aeration — the latter a legitimate 

 word in actual use — defining ventilation 

 as the process of letting the external air 

 at once into a forcing-house, and aeration 

 as the act of keeping the atmosphere of 

 a forcing-house in motion by currents of 

 warmed fresh air. The importance of 

 aeration cannot be over-estimated. It is 

 the one thing which now requires to be 

 secured, in order to render our artificial 

 climates natural. A man's reason, in- 

 deed, must tell him, that a plant con- 

 demned to pass its life in a still atmos- 

 phere, is like nothing so much as a 

 criminal set fast in an everlasting pillory. 

 In order to secure motion in the vege- 

 table kingdom, currents of air are made 

 to do the work of the muscles, limbs, 

 and volition of animals. It is not at 

 all improbable that, in addition to the 

 mechanical effects of motion in assisting 

 the propulsion of the sap, it may be 

 important that the stratum of air in 

 contact with the leaves of plants should 

 be incessantly shifted, in order to enable 

 them to procure an adequate supply of 

 food; for we find that water in motion 

 feeds them better than that which is 

 stagnant. Leaves are continually ab- 

 stracting from the air the very minute 

 quantity of carbonic acid which it con- 

 tains. When the air moves quickly over 

 their surface, fresh supplies of that food 

 are incessantly presented to it, and 

 the operation of abstraction may be 

 facilitated ; while, on the contrary, if the 



