36 



a great number of holes for giving a passage to the 

 air. 



These perforated earthen pans, which are made very 

 thick and strong, are incomparably cheaper than iron 

 grates; and judging from the experience I have had 

 of them, I am inclined to think they answer even better 

 than the grates ; indeed it appears to me not difficult to 

 assign a reason why they ought to be better. 



For large fire-places I have sometimes used grates, 

 the bars of which were common bricks placed edgewise, 

 and these have been found to answer very well. 



As only that part of the air which, entering the fire- 

 place in a proper manner and in a just quantity, and 

 coming into actual contact with the burning fuel, is 

 decomposed, contributes to the generation of heat, it is 

 evident that all the air that finds its way into the fire- 

 place, and out of it again, without being decomposed, 

 is a thief ; that it not only contributes nothing to the 

 heat, but being itself heated at the expense of the fire, 

 and going off hot into the atmosphere by the chimney, 

 occasions an actual loss of heat ; and this loss is often 

 very considerable, and the prevention of it is such an 

 object, that too much attention cannot be paid to it in 

 the construction of fire-places. 



When the fire-place is closed on all sides by a wall, 

 and when the opening by which the fuel is introduced 

 is kept closed, no air can press in laterally upon the 

 fire ; but yet, when the grate is larger than the heap of 

 burning fuel, which must often be the case, a great 

 quantity of air may insinuate itself by the sides of the 

 grate into the fire-place, without going through the 

 fire. But when, instead of an iron grate, a perforated 

 hollow earthen pan is used, by making the bottom of 



