MANAGEMENT OF THE ATMOSPHERE. 287 



mismanagement of some kind or other exists, that they can 

 possibly be productive of injury, or even of inconvenience. 



These considerations, then, would seem to point out the fact r 

 that the admission of air to any extent in forcing-houses in win- 

 ter, or at a very early period of the season, cannot be said to be 

 a matter of urgency, or necessity ; neither can it be grounded on 

 the plea that many of our practical operations have for their 

 foundation, viz., an expedient for a better, and probably more 

 tedious, method of effecting the same results. Whatever impro- 

 priety may appear in the above statement, it will be fully justi- 

 fied by its truth, if a dozen years' extensive practice in the 

 management of hot-houses, both large and small, and in the 

 working of forcing-houses throughout the winter, be worth any- 

 thing, as well as the evidence of many of the best practical 

 gardeners of the present day. Then we would say that the 

 influx of large volumes of cold air is decidedly hurtful, even on 

 other grounds than those advanced in a former part of this chap- 

 ter. But, on the other hand, the opposite extreme must also be 

 avoided. The process may not be altogether dispensed with, 

 although every means ought to be taken to modify its immedi- 

 ate effect upon the internal atmosphere. It does appear, never- 

 theless, that the regulation of the internal temperature, i. e., the 

 prevention of too powerful a degree of heat, when the source of 

 that heat is the sun, is the only legitimate end to be effected by 

 the practice. If there are any other real advantages, they are 

 certain to follow. If air is admitted with this only in view, 

 and these advantages are not likely to be lost if air is not admit- 

 ted when not required to effect this primary purpose, periods 

 of bright sunshine, then, may be regarded as the only instances 

 in which a recourse to the practice is absolutely necessary. 



3. From a full investigation and consideration of this sub- 

 ject, the conclusion at which we hare arrived is, that, with a 

 proper system and routine of management, as regards the 

 application of atmospheric humidity and heat, the admission of 

 large volumes of the external air into the interior of hot-houses 

 is not by any means so essential as it is generally represented 

 to be. Whatever other differences of opinion may exist with 

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