Mr. J. C. Maxwell on the Dynamical Theory of Gases. 201 



was filled with the first gas, and the proportion of the first gas 

 in the tenth of the tube atthe other end ascertained after a time 

 t, this proportion will' be 



7 t-— ^< e " 2 sin 2 — — < 



p 10 r L 10 



»7r 2 r> . „. ^ 



" sm 3 10 I 



— &C.J- 



+ e~ 32 ^'sin 2 3 " 



1 



a series of 

 time T, where 



We find for a series of values of — taken at equal intervals of 



p * 



log g 10a g 

 i_ 10tt 2 D 



Time. 







T -01193 



2 T -02305 



3 T -03376 

 4T -04366 



5 T -05267 



6 T -06072 

 8T -07321 



10 T -08227 



12 T -08845 



oo -10000 



Mr. Graham's experiments on carbonic acid and air, when com- 

 pared with this Table, give T = 500 seconds nearly for a tube 

 0-57 metre long. Now 



log^lO^ 



10tt 2 T' ' ' ' * ' ' ^ J1) 

 whence 



D = -0235 



for carbonic acid and air, in inch-grain-second measure. 



Definition of the Coefficient of Diffusion. 



D is the volume of gas, reduced to unit of pressure, which 

 passes in unit of time through unit of area when the total pres- 

 sure is uniform and equal to p } and the pressure of either gas 

 increases or diminishes by unity in unit of distance. D may be 

 called the coefficient of diffusion. It varies directly as the square 

 of the absolute temperature, and inversely as the total pressure^. 



