346 THE APPLICATIONS OP PHYSICAL FORCES. [BOOK iv. 



attain with ease to 85 or 90 per cent, of the heat developed by the 

 combustion. Although the ventilation caused by the draught is 

 altogether insufficient, according to M. Morin the air of a room 

 warmed by a stove is renewed afc the oftenest once in every 

 ten hours. 



Fig. 238 represents a heating stove, the arrangement of which is 

 very advantageous, both with reference to ventilation and utilisation 

 of the fuel. Ventilation is secured by an inlet air- pipe, which opens 

 below the grate at A ; a plug P allows the introduction of fresh air. 



FIG. 238. Heating and ventilating stove. 



FIG. 239. Section of a north country stove. 



and consequently the draught to be regulated, The smoke, escaping 

 by a flue-pipe at the side, warms the air in the chamber, whence it 

 escapes by expansion through the lateral ventilators into the room. 

 The outer covering B also prevents the injurious effects which might 

 result from the overheating of the iron case containing the fuel. 



