22 HEAT 



As the air is heated by the fire, it expands and is pushed up 

 the chimney by the cold air which is constantly entering through 

 loose windows and doors. Open fireplaces are very healthful 

 because the air which is driven out is impure, while the air 

 which rushes in is fresh, and brings oxygen. 



But open fireplaces, while pleasant to look at, are not effi- 

 cient for heating, because most of the heat escapes through the 

 chimney and only a small portion remains in the room where 

 warmth is needed. Neither are open fireplaces practical for 

 cooking, because there is no convenient arrangement for plac- 

 ing cooking utensils over the burning fuel. Owing to the loss 

 of heat from open fireplaces, and their inconvenience in cook- 

 ing, the invention of stoves was a great advance in efficiency, 

 economy, and comfort. A stove is a receptacle for fire, pro- 

 vided with a definite inlet or draft for air and a definite outlet 

 to the chimney for smoke, and able to radiate into the room 

 most of the heat produced from the fire which burns within. 

 The inlet, or draft, admits enough air to cause the fire to burn 

 brightly or slowly, as the case may be. When we wish a hot 

 fire, the draft should be opened wide and enough air secured to 

 produce a strong glow. When we wish a low fire, the inlet 

 should be partly closed, and just enough air admitted to keep the 

 fuel smoldering. 



When the fire is started, the outlet damper should be opened 

 wide in order to allow the escape of smoke ; but after the fire is 

 well started there is less smoke, and the damper may be partly 

 closed. If the damper is kept open, coal is rapidly consumed, 

 and the additional heat passes out through the chimney and is 

 lost. 



Furnaces. Hot air. The labor involved in the care of 

 numerous stoves is considerable, and the use of a central 

 heating stove, or furnace, is a great saving in strength and 

 fuel A furnace is a stove arranged as in Figure 12. The 



nd 



1 



