430 



MATHEMATICAL APPENDICES 



Of the N molecules contained in unit volume, Maxwell's law 

 gives 



as the number which move with a speed w or with a speed differing 

 infinitely little from w. According to the preceding article these 

 B/r 



FIG. 5 



w/Ct 



2. 



FIG. 6 



particles attain on the average a free path I = w/B. If therefore 

 N is a number sufficiently great, the sum of all the paths which 



