DEVELOPMENT OF HOUSE HEATING 143 



huge bonfire and the draft up the chimney was intense. To 

 replace the large amount of air which passed up and out of the 

 chimney, a blast of cold air poured in at every crack and 

 crevice. A cold current was always crossing the room from 

 the outside wall to the chimney. Probably nine-tenths of 

 the heat was swept up and out of the chimney without warm- 

 ing the room at all. Only a little of the heat passed back 

 into the room, and that was by RADIATION. It is an old say- 

 ing that the old-fashioned fireplace roasted one side of a 

 person while the other side froze (Art. 79). 



168. The Common Modern Grate. The common grate of 

 today is not used extensively in the northern states for heat- 

 ing purposes. It is generally regarded as a secondary heat- 

 ing plant to be used in the fall and spring or in conjunction 

 with some other system of heating in the winter. In the 

 southern states, where little artificial heat is needed, it is often 

 the only heating plant. 



The modern grate consumes but little fuel compared with 

 the old-time fireplace. The flue is much smaller and the 

 amount of air passing up the chimney far less. The " roast- 

 ing and freezing" effect is not nearly so marked as in the case 

 of the old-fashioned fireplace. Still the efficiency is very 

 low. Usually not more than 12 or 15 per cent, of the heat 

 generated is utilized in heating the room in which the grate 

 is placed. But even then, this common grate is invaluable 

 from a sanitary point of view as will be shown later when 

 considering ventilation (Chap. VI). 



169. The Modern Ventilating Grate. The efficiency of a 

 grate is very greatly increased by constructing it with a flue 

 up the back and the sides through which a current of fresh air 

 passes. The air is admitted through a pipe in the basement, 

 and after being heated in the flue, passes into the room through 

 a grating above the open fire (Figs. 104 and 105). This 

 constitutes an inlet for as much fresh air as is removed from 

 the room by the draft up the chimney, and prevents the cold 

 draft from the outside walls (Fig. 106). While the com- 



