SCIENCE OF COMMON THINGS. 219 



Advantages of stoves over fireplaces. Disadvantages of stoves. 



with its heat for any useful purpose. In addition to 

 this, a quantity of the air of the room, which has been 

 warmed by radiation, is uselessly carried away by the 

 draught. 



1459 What are Vie advantages of a stove over an open fireplace ? 



1. Being detached from the walls of the room, the 

 greater part of the heat produced by combustion is 

 saved. The radiated heat being thrown into the walls 

 of the stove, they become hot, and in turn radiate heat 

 on all sides to the room. The conducted heat is also 

 received by successive portions of the air of the room, 

 which pass in contact with the stove ; 



2. The air being made to pass through the fuel, a 

 small supply is sufficient to keep up the combustion, so 

 that little need be taken out of the room ; and 



3. The smoke, in passing off by a pipe, parts with 

 the greater part of its heat before it leaves the room. 



1460 What are the disadvantages of stoves ? 



Houses containing them are generally ill ventilated. 

 The air coming in contact with the hot metal surfaces 

 is rendered impure, which impurity is increased by the 

 burning of the dust and other substances which settle 

 upon the stove. The air is, in most cases, kept so dry 

 as to render it oppressive. 



1461 Upon what principle are the common hot-air furnaces for warm- 



A stove, having large radiating surfaces, is inclosed 

 in a chamber (generally of masonry). This chamber 

 is generally built with double walls, that it may be a 

 better non-conductor of heat. A current of air from 

 without is brought by a pipe or box, and delivered un- 

 der the stove. A part of this air is admitted to supply 

 the combustion ; the rest passes upwards in the cavity 

 between the hot stove and the walls of the brick cham- 

 ber, and, after becoming thoroughly heated, is con- 

 ducted through passages in which its lightness causes 

 it to ascend, and be delivered in any apartment of the 

 house. 



