348 THE APPLICATIONS OF PHYSICAL FORCES. [BOOK iv. 



the sides, all over the apartment. In other cases (Fig. 239) the 

 inside of the stove is simply divided into chambers or compartments 

 one over the other, within which the smoke and the gases of combus- 

 tion circulate. In this case it is simply by radiation from the outside 

 that the warming takes place. In general it is sufficient to keep 

 such a stove alight for a few hours in the morning, and then to close 

 the apertures when the whole of the fuel is in a state of incan- 

 descence. The feeble conductivity of the clay or glazed porcelain 

 which forms the outer cover then preserves the heat of the apparatus 

 for the whole day. 



