OF THE ATMOSPHERE OF HOT-HOUSES. 323 



The striking difference which is exhibited between our con- 

 servatories and green-houses in this country, and those of Eng- 

 land, is not so much owing to the existing peculiarities of cli- 

 mate, as to the methods of practice adopted by the gardeners 

 themselves in the management of the atmosphere of their 

 houses. However costly and faultlessly a conservatory, a hot- 

 house, or a grapery, may be constructed, the whole success of 

 the structure depends upon the subsequent management of its 

 atmosphere. 



The imitation of warm climates in winter, for the purpose of 

 preserving tender plants, must not be confounded with the arti- 

 ficial climate created in a hot-house for the purpose of forcing 

 or accelerating foreign or native productions. As two different 

 objects are sought for, different courses of procedure must be 

 adopted. All that is necessary for the preservation of green- 

 house plants, is to keep the atmosphere at night a few degrees 

 above the freezing point ; and, indeed, if a proper attention be 

 paid to the plants, so as to avoid an excess of moisture, there is 

 scarcely any kind of w^iat are generally termed hot-house plants, 

 that will not thrive well enough under similar treatment. We 

 have often allowed our plant-houses to fall below the freezing 

 point in very severe nights; and when long and continued frosts 

 set in, the plant-houses should be gradually inured to bear even 

 a few degrees of frost below 32° ; and this the plants will do 

 without injury, if they be kept in a proper condition. When 

 the external atmosphere is dry and mild, air should be admitted 

 freely to the green-house during winter, but closed early in the 



R'hich, being less affected by the sun than the earth, imbibes less heat 



m summer, and, from its fluidity, is less early cooled in winter. As the 



sea on the coasts of Britain never freezes, its temperature must ahvays 



be above 33^ or 34° ; and hence, when air from the polar regions, at a 



much lower temperature, passes over it, that air must be in some degree 



heated by the radiation of the water. On the other hand, in summer, 



the warm currents of air from the south necessarily give out part of 



their heat in passing over a surface so much lower in temperature. 



The variable nature of its climate is chiefly owing to the unequal 



breadth of watery surface which surrounds it, — on one side a channel 



of a few leagues in breadth, on the other, the broad Atlantic Ocean. — 



iLoudon's Encij. of Gard.] 



28 



