Ventilation and Heating. . 115 



For the cold air is heavier than the warm air and continu- 

 ally pushes the warm air up and out of the room wherever 

 it can. But the stove does not send as much air up the 

 chimney as the grate does, and so does not draw in as 

 much fresh air. It is therefore not a good ventilator. 

 But the stove gets much more heat from a given amount 

 of fuel. 



A Stove and Jacket. In some cases a jacket is placed 

 around a stove, and a duct from the outer air connects 



Fig. 62. The Unjacketed Stove. 



with the lower part of the space inside of the jacket and 

 outside of the stove. Then as the air heated by the stove 

 rises, fresh air is drawn in from outside to be warmed. 

 In this case the direct heat from the stove is shut off from 

 the room. Heat radiates in straight lines. When one 

 holds out his hands beside a stove, the heat he receives 

 is radiant heat. Most of the heat from a grate is radiant 

 heat. But in a jacketed stove the heating by air currents 

 is called heating by convection. 



