518 BESSEL ON BAROMETRICAL 



Nitrogen gas = 0-9691 T> = d D 



Oxygen gas = 1-1026 B — d, I> 



Carbonic acid gas = 1-5260 D = d„ D. 



These six numbers require to be slightly altered, in order that 

 they may correspond to the relation 



I =vd + v,di + v,idii (1.) 



Designating by M, ?«, m^, ?«;„ the masses, and by D, 8, 8^, S^,, 

 the densities of the mixture and of its constituent parts, we 

 have, on the supposition of equal distribution in the space, 



D :M - h : m = ^, : m, = ^ii-.m,,; . . . (2.) 



further, if P, p, pj, p^ denote' the pressures which the mix- 

 ture and its constituent parts, the latter taken separately, exert 

 on the unit of surface of the enclosing space, we have by Ma- 

 riotte's law, 



F:d jy = p :B 



P :d,D = J9, : 8, 



P:d„D = p„'h> 



and also 

 thus 



1 =p:v=pi:v,=pi,:v„ 



^ = V dD; hi = VidiI>; 8^^ = v,, d^ D. 



Introducing these values of 8, 8^ 8^, into the above proportion 

 (2.), we obtain 



m = vdM, m, — Vi d^ M, ntn = v^ d,, M, 



and as M = m + m, + nin, we have also the relation (1). To 

 satisfy this relation I have slightly altered d and dj, making the 

 first 0-9711, and the second 1-1048. 



Biot and Arago determined the density of atmospheric air 

 [L e. the mixture of the three gases) at the surface of the earth, 

 at the temperature of melting ice, and under a pressure of a 

 column of mercury of the same temperature in the 45th parallel 

 of latitude of 336-905 Parisian lines, to be 10466*8 times less 

 than that of mercury. Under the aforesaid circumstances, there- 



^•^^^' ^ = loiWs- 



As the temperature increases, the specific elasticity of the air, 

 or the space which a given quantity of air occupies, increases 

 also, the pressure remaining equal. Gay Lussac arrived at the 

 remarkable result that the specific elastic force of all gases and 



