;202 ELEMENTARY SCIENCE 



a window both at the top and at the bottom^thus providing 

 two openings ? 



After fireplaces came stoves, which are simply fire-holders 

 so built that the consumption of fuel is economical and 

 the transfer of heat is into the room rather than up the 

 chimney. An important feature of the stove is the draft 

 whereby air is admitted from below to provide the oxygen 

 necessary for the burning of the fuel; the rate at which 

 the fire burns may be controlled by the opening or closing 

 of the draft. In the case of fireplaces, andirons are used to 

 secure the needed draft of air from below. The draft 

 (drawing) of air through the stove is also controlled by a 

 damper, which is a movable plate by means of which the 

 flue may be open or closed. 



The closing of the flue, through which the hot gases 

 from the fire flow, checks the draft, and so lowers the rate 

 of burning. It also checks the heat from going up the 

 chimney. So the damper is usually left open while the 

 fire is starting, and then closed or partly closed when the 

 fire is burning well. We should remember that wood and 

 coal in burning give off gases, and it is the burning of these 

 gases as well as the burning of solid fuel that produces the 

 heat we feel. So we see that stoves have another advantage 

 over fireplaces in that they give us the benefit of the heat 

 from these burning gases more than fireplaces do. 



A furnace is better than a stove in that, by means of 

 it, the heat of a single fire may be conveyed over the 

 whole house. It permits of greater economy in the con- 

 sumption and in the transportation of fuel, as well as 

 in the distribution of heat. A furnace, strictly speaking, 

 is that part of a heating plant in which the heat is gener- 

 ated. For the conveyance of this heat to other points, 



