CHAP. I.] 



THE ART OF WARMING. 



343 



the warm gaseous products of combustion, 1 the calorific effect of 

 these fireplaces is extremely feeble, and we are led to seek more 

 rational arrangements, and to invent those which are known as 



ventilating fireplaces. 



III. VENTILATING FIREPLACES. 



The principle of the ventilating fireplace is as follows : Instead 

 of drawing from outside, through the chinks of doors and windows, 

 or even by ventilators and side-conduits, 

 the air which is required for the draught, 

 and indispensable for the renovation of the 

 vitiated air of the room, it is attempted to 

 prevent the fresh cold air from entering till 

 after its temperature has been raised by 

 means of the fire itself. The air from the 

 outside is therefore made to circulate in the 

 passages surrounding the grate, and when 

 heated it is made to escape by ventilators 

 into the room itself, and thus contribute to 

 raise the temperature. 



Various arrangements have been in- 

 vented for this end. We will mention only 

 two of the most simple. 



In one (Fig. 236) the air comes from the 

 outside by a passage which entirely sur- 

 rounds the iron cylindrical flue, and also a 

 part of the grate ; it thus becomes warm, 

 and rises to an opening made near the 

 ceiling in the wall of the room. It is thus 

 warm air, and at the same time fresh and 

 unvitiated, that replaces what is .consumed 

 in the act of combustion or drawn off by 

 the draught. 



1 According to General Morin, the air which leaves the grate is often at a tem- 

 perature of 60, 80, 100 Cent, or more. The loss of heat amounts to S X | or more 

 of this dispersed heat, and the calorific effect of an ordinary fireplace scarcely 

 exceeds '14 or '12 of the heat developed by the combustion. 



a 



FIG 236. - Douglas Galton's 

 ventilating fireplace. 



