Ventilation of Rooms, Sfc. 117 



compensate for the loss of velocity occasioned by the heat 

 subtracted from the ascending air. 



The ascent of gases through flues of furnaces may easily 

 be ascertained in the same general manner, attending only to 

 the specific gravities of the compound fluids. 



Suppose the whole combustible matter to be pure carbon, 

 and that it converts the entire oxygen of the atmospheric air 

 passing through the furnace into carbonic acid. 



Then, since 5.7 parts by weight of carbon unite with 15 of 

 oxygen, (the sp. gravity of which is 1.1175), into the same bulk, 

 the specific gravity of carbonic acid must be 1.542 : but the ni- 

 trogen, which constitutes 77 parts in an hundred of atmospheric 

 air remaining unaltered with a specific gravity 0.9649, the 

 specific gravity of the whole will be 10874. And 1 part by 

 weight of carbon will require for its complete saturation 2.63 

 parts of oxygen, or 11.44 parts by weight of atmospheric air. 

 Let the instance taken be a smelting furnace, heated to 1500° 

 of Fahr. above the surrounding atmosphere, which is probably 

 about the temperature of a copper furnace, and let the con- 

 sumption be twice 84 pounds of carbon in an hour. The rare- 



faction will be x =z — =r 22.68 g = 1.0874 — =: 20.86. 

 480 ^ g 



Let I or the length of the stock be 40 feet, then v ~ 226 feet in 



a second, and the quantity of matter, reduced to atmospheric 



density, issuing through one square foot in a second will be 



10.84, or in an hour 39022 cubic feet. But, from what is 



stated above, 168 pounds of carbon will unite with the oxygen 



of 1922 pounds of atmospheric air, and assuming 13.2 cubic 



feet, as equal to a pound at a mean temperature, the whole 



will constitute 25.375 cubic feet; but these must be increased 



in the proportion of the specific gravity which makes them 



27.591. And the quantity issuing in an hour has been found 



to be 39022, therefore the aperture must be of about 102 



square inches. 



At the degree of temperature producing the maximum effect, 



the same weight of these electric fluids would pass through 



an aperture of rather less than half the size : but, if the matter 



