VevtUatio7i of Rooms, S)C. 115 



the log. 3.0439084. If the elastic fluid has a density one-half 

 of the surrounding medium, or gr = i, the greatest escape will 

 be when the temperatures are equal : and when the specific 

 gravity is less than ^ the degrees of temperature will become 

 negative. 



Thus hydrogen, with a specific gravity 0.0694 = g, gives 

 Jr = 0.1388 M = — 949°, and the greatest quantity will escape 

 by Its levity through a given aperture at the temperature of 

 949° below the surrounding atmosphere; on the supposition 

 that temperatures and densities continue through so extensive a 

 range to be connected by the same law. 



In applying these theorems to the case of ventilating an 

 apartment, little attention need generally be bestowed oi^ 

 minute accuracy. The tendency to ascend, which must be the 

 same in a room as through a tube of equal length, may be de- 

 duced from the mean of three or four observations on the tem- 

 perature made at different elevations; and the height of the 

 room should include the perpendicular length of any apparatus 

 for conducting the air into the atmosphere ; and, if it is thouojit 

 of sufficient importance, a value may be assigned to g, cor- 

 responding with the subtraction of oxygen, and the presence of 

 carbonic acid, then substituting the numerical values for 



~k'^^~~^- The square root of this quantity multiplied by m, 

 and divided by the square root of the density of the upper 

 stratum of air, will give the velocity ; and this again multiplied 

 by the density of the same stratum, and by the section of 

 the aperture in square feet, will give the number of cubic 

 feet issuing in a second, reduced to atmospheric density. In 

 practice, however, it will be quite sufficient to use a mean 

 density throughout. 



To assume a case, let it be required to extricate from an 

 apartment sixty feet long, thirty feet wide, and thirty feet high, 

 a quantity of air equal to its whole content of atmospheric 

 density in an hour, by means of an average increased tem- 

 perature of 20'' of Fahrenheit. The rarefaction for 20°, or 



12 



