56 MOLECULAR MOTION AND ITS ENERGY 28 



28. Values of the Speeds 



In order to give a clearer idea of these relations I have 

 calculated a few examples of numbers, and more especially 

 for the two gases which are the most important constituents 

 of atmospheric air, namely, oxygen and nitrogen. The 

 densities of these gases, according to Jolly, 1 are 

 p = 0-0014291 for oxygen 

 = 0-0012576 nitrogen, 



when at under the pressure of a mercury column 0'76 m. 

 high at Munich, where the acceleration " of gravity is 

 9-8069 m. per sec. per sec. We therefore obtain for the 

 Joule-Glausius mean values at 



G = 461-2 m. per sec. for oxygen 

 = 491-7 nitrogen, 



which completely agree with the values given in 13, as 

 deduced by Clausius from Eegnault's observations. 

 From Maxwell's law we obtain for the arithmetic means 

 of the molecular speed at 



O = 424-9 m. per sec. for oxygen 

 = 453-0 nitrogen. 



The mean probable values at are 



= 409-5 m. per sec. for oxygen 

 = 436-6 nitrogen, 



and, finally, the most probable values of the speed at are 



W = 376 '6 m. per sec. for oxygen 

 = 401*4 nitrogen. 



Lord Eayleigh 2 found hydrogen to be 15-884 times lighter 

 than oxygen, and consequently for hydrogen at 



G = 1838-2 m. per sec. 

 - O = 1693-6 

 = 1632-2 

 W = 1500-9 



The law of the unequal distribution of different speeds is 



1 Abh. d. Akad. zu Miinchen, xiii. 2. Abth. ; Wied. Ann. vi. 1879, p. 520. 



2 Proc. Roy. Soc. xxiii. 1888, p. 356. 



