496 Of the Management of Fires 



and passing over the surface of the burning fuel 

 entered the flues of the boiler with the flame, cooled 

 the bottom of the boiler almost as fast as the flame 

 heated it. 



The waste of heat that is occasioned precisely in 

 this manner in the fire-places of steam-engines, brewers' 

 coppers, distillers' coppers, etc., must be very great in- 

 deed. To be convinced of this fact, nothing more is 

 necessary than to see how very imperfectly the entrance 

 into one of these fire-places is closed by its single door, 

 ill fitted to its frame ; what a length of time the door is 

 left wide open while the fire is stirring or fresh coals are 

 putting into the fire-place ; and what an impetuous tor- 

 rent of cold air rushes into the fire-place on those 

 occasions. 



As the cold air that comes into the fire-place in this 

 manner, and passes over the burning coals, has very 

 little to do in promoting the combustion of the fuel, 

 and must necessarily be heated very hot in passing 

 through the fire-place and through the whole length 

 of the flues of the boiler, it is easy to see what an 

 immense quantity of heat this air must steal and carry 

 off into the atmosphere in its escape up the chimney. 



To remedy this evil, the doors of all closed fire- 

 places should be double, and they should be fitted to 

 their frames with the greatest nicety, which may easily 

 be done by making them shut against the front edge 

 of their frames, instead of being fitted into them or into 

 grooves made to receive them ; and, when the fire is 

 burning, these doors should beopened as seldom as 

 possible and for as short a time as possible. I have 

 already mentioned the necessity of these precautions in 

 my sixth Essay, but they are of so much importance 



