AND CONSEETATOET. 13 



CHAPTEE IT. 



HEAT1>'G THE PLANT HOUSE. 



The heating of plant-houses presents a difficulty propor- 

 tioned to their size in an inverse geometrical ratio. To put 

 the case in another way, it may be said, that the larger the 

 house or group of houses to be heated the more easily may the 

 desired end be accomplished, but the smaller the house the 

 more difficult the task. In the preceding chapter it is re- 

 marked that the atmosphere of a small house is quickly influ- 

 enced by changes of external temperature ; and here it may be 

 added that it is equally soon affected by the action of any kind 

 of heating apparatus. Hence, the amateur who finds his plants 

 hard frozen may light a fire to save their lives, and actually 

 roast them to death in an hour or two, through indiscreet 

 management. Nevertheless, the amateur who has but one small 

 house need not be discouraged by this statement, for it is a 

 part of the ostensible purpose of this book to render aid in this 

 extreme but not uncommon case, as well as in the broader sub- 

 ject of heating in general. 



It is of the utmost importance that the mode of heating 

 should be thought of when a plant-house is designed in the 

 first instance, because heat is generated and diffused, in ac- 

 cordance with fixed laws, to which all our arrangements must 

 conform. Thus, if we build a house in a low, swampy posi- 

 tion it will be found a difficult matter to give it the benefit of 

 artificial heat by any means whatever, because as heat ascends 

 from the level at w'hich it is produced, it follows that the heat 

 generator or furnace must be placed at a lower level than the 

 house itself, and, in the case of a house in a swamp, the only 

 place for the furnace will be in the water. This is another ex- 

 treme case for which, so far as the laws of nature permit, we 

 shall endeavour to provide ; and it is cited simply for the pur- 

 pose of impressing the amateur plant-grower with the neces- 



