336 



JEconomy of Fuel. 



It will be found that the least portion of temperature abstracted 

 was thirty-three and a third per cent of the excess, with which the 

 gas entered the drum ; and this occurred when a quantity of cold 

 anthracite had just been added to the fire, which greatly reduced the 

 temperature of the gas. The drum in the mean time retained some 

 portion of its previous temperature and imparted to the gas instead 

 of taking from it, a quantity of heat. The greatest per cent was for- 

 ty-seven and a half, which was abstracted when the temperature was 

 rising very rapidly and when, of course, the iron of the drum, as well 

 as the air of the room was acquiring temperature. It also occurred 

 when the fire was covered with cinders and the fire-doors opened at 

 night ; the slowness of motion in the gas having apparently more than 

 counterbalanced the diminution of tension in the heat, and allowed 

 a greater portion of the excess to escape. 



The result of all the above observations is, that with a temperature 

 in the room, varying from 56° to 72°, and in the entering gas, from 

 100° to 231°, the number of degrees of heat abstracted by about thir- 

 ty-eight square feet of surface, varied, (according to the tempera- 

 ture,) from 16° to 63°, showing, when compared with the excess of 

 the gas above that of the room, a portion abstracted equal to ^%%\ 

 of that excess, or about one per cent for each foot of metallic sur- 

 face. 



