Houses and other Buildings. 231 



which are exposed to the direct rays, and would become un- 

 equally heated in the inverse ratio of their conducting power. 



When bodies are immersed in a heated medium, such as in 

 air or water, they receive their heat on every side ; and it has 

 been found by experience, that this mode of applying heat is of 

 particular importance in the economy of animals and vegetables. 



Nothing can be more unphilosophical than the common mode 

 of warming ordinary rooms by open grates. To put an ex- 

 treme case of this mode of warming, we have only to instance 

 the effect of making a fire in the open air. In this instance, 

 there is free access for the ascent of the rarefied current, and 

 the lateral current rushing towards the fire is felt on every side, 

 supposing no natural breeze prevailed. The effect of this cold 

 current is so conspicuous on the human body, that few unac- 

 customed to such exposure would escape some variety of those 

 affections called colds. 



Our common dwellings approach this extreme case in pro- 

 portion to the size of the fire, the width of the chimney, and 

 the access of cold air by the doors and windows. In every 

 case, as much cold air must be admitted as will effect the 

 combustion of the fuel, and supply the demands of respiration. 

 The air which would be barely sufficient for these purposes, 

 coming immediately from a cold atmosphere into rooms with 

 grates even of the best construction, will ever be a barrier to 

 that comfort which we ought to experience, and which by 

 the aid of other means can be easily attained. 



Notwithstanding the absolute necessity of admitting a certain 

 portion of fresh air into every room, it is a common practice 

 with builders to make doors and windows so tight as frequently 

 to be the sole cause of a smoky chimney. To obviate this evil, 

 some have let in a certain quantity of atmospheric air under or 

 near to the fire grate. By this expedient, those sitting around 

 the fire are not annoyed by the cold current, but an inconve- 

 nience arises from this contrivance, which more than counterba- 

 lances its benefits. The air entering the room so near the fire 

 immediately supplies the current up the chimney without chang- 

 ing the air of the room, A crowded room, and the presence of 

 R2 



