FART V. CULINARY GARDENING. 293 



reason why hot-houses with glass on all sides are so difficult 

 to manage without this improvement. 



Soil is obtained either by inclosing a portion of the ground 

 surface, and preparing it in a proper manner; or by placing 

 it in pots or boxes, which may be removed or altered at plea- 

 sure. 



Air, it is almost unnecessary to observe, is inclosed, and can 

 be excluded, and fresh air admitted, either wholly or to mix 

 with it, by having apertures at different places, which may be 

 opened or shut at pleasure. 



Light is admitted by constructing all or part of the roof, or 

 even the sides and the roof together, of glass frames. 



Water as such, that is in its fluid state, is easily given to the 

 plants by pouring it on the ground only; as rain, it is given by 

 the syringe, or engine, or watering-pot; and as dew, by pour- 

 ing it upon hot masonry, such as the flues, by which it first 

 ascends as steam, and then descends, on parting with its calo- 

 ric, as dew. 



Wind, which has two effects, that of putting the plants in 

 motion, and removing stagnated air, is produced by admitting a 



