Economy of Fuel. 229 



Exp. 2. The air was now 26°j parlor, 70°; the air at top, 118°; 

 three feet below, 123°; six feet below, 131°; nine feet below, 137°; 

 ten and and a half feet below, 139, showing an average diminution of 

 2° per foot, in the height of the chimney as the gas approached 

 the top. 



Exp. 3. This was a cold day and a brisk fire was maintained. 

 The air was at 18°; the parlor, 75°; gas at the top, 180°, and 

 twenty one feet below, 220°, showing a diminution of 1 j%° for each 

 foot of the height, and demonstrating that the gas had, at its escape, 

 nearly thrice as much excess above the surrounding air, as any 

 room in the house. The temperature at which the gas escapes, 

 must obviously depend upon the state of the fire, as well as upon the 

 quantity of unburnt air, which obtains admission above it. When the 

 fire door of the stove is open, the air enters rapidly and mixing with 

 the gas, partakes of its heat, but probably derives from the fire above 

 which it passes, a small part only of its ultimate temperature. The 

 same is true of the air which enters at the throat of a chimney, be- 

 neath which a grate is in action. The air which approaches to mix 

 with the gas, continues cold until the moment of passing the throat, 

 and in this current of cold air, the hand may be held with impuni- 

 ty, while just within the throat the temperature is that due to the 

 mixture of hot gas and cold air. If this throat be much larger than 

 is necessary to receive the gas, a greater proportion of the air of the 

 room will there find an outlet, and the useful effect of the fuel will 

 be neutralized by sending up the chimney that air which it was the 

 chief purpose of the fire to warm, in order that it might be retained 

 in the apartment and applied to its occupants. 



Exp. 4. This experiment was made upon a chimney, the gas from 

 which was derived from an open grate in the basement, and of course 

 contained much common air, mixed with the products of combustion. 

 The open air was at 50°, the escaping mixture at 120°. 



Exp. 5. A similar examination of another chimney fed by a large 

 kitchen range in full action, gave 125° for the temperature of the 

 gas, that of the open air being 45°. The foregoing experiments 

 served to indicate, that the gas of a close stove, if not of an open 

 grate, might be usefully employed to warm an additional apartment, 

 since it constantly escaped at a much higher temperature than it 

 could be desirable to maintain in any part of a dwelling. 



To effect the proposed saving, it was only necessary to arrest the 

 gas by a partition at the proper point, perforate the side of the chim- 



VoL. XXIII.— No 2. 42 



