ACTION OF THE ATMOSPHERE, ETC. 11 



and be coved, so as to collect the rays of the sun and re- 

 flect them into the house. 



In order to protect hothouses and greenhouses from 

 humidity, they must be warmed and aired at the same 

 time : the heat both dissolves the moisture and prevents 

 the plants from suffering from the external air while the 

 windows are open ; and the current of air carries off any 

 moisture which is not dissolved. 



The finest hothouses are in Russia, where the wealth 

 of the higher classes enables them to indulge in luxuries. 

 In their cold climate, hothouses and greenhouses are 

 considered as necessary articles of comfort. In England, 

 Mr. Loddiges' establishment at Hackney exhibits the 

 most perfect model of hot and greenhouses : they are 

 warmed by vapor, and when necessary, watered by the 

 tepid water into which the steam is condensed. The 

 building is one thousand four hundred feet in length, and 

 divided into compartments, each of a different tempera- 

 ture. 



Emily. What effect has the tan which is used in hot- 

 houses ? 



Mrs. B. It produces heat, by undergoing a degree of 

 fermentation ; but it also generates humidity, and heat 

 and humidity favor the propagation of fungi and of worms ; 

 and should the roots of the plant grow below the pot, and 

 penetrate into the tan, its contact is injurious. 



The smaller and lower the house, the more favorable it 

 is to young and delicate plants : the heat always rises, so 

 that in large and elevated houses the small plants of the 

 lower range are situated in an atmosphere of cold air 

 It is for this reason that slips of greenhouse plants are 

 generally placed in beds covered with glass in order to 

 strike root, where they receive as much heat in as small 

 a space as possible. 



CONVERSATION IX. 



ON THE ACTION OF THE ATMOSPHERE ON VEGETABLES 



Mrs. B. This morning we shall turn our attention to 

 the manner in which the atmosphere affects the vegetable 



676. And of warming and airing them ? 677. Where are the best 

 hothouses ? 678. What description is given of the one mentioned in 

 England ? 679. What is said of the use of tan ? 680. Why arc 

 slips of greenhouse plants generally placed in beds covered with glass? 



11 



