

Velocity <>/ Swiftly Moving Electrified Particle 



» ( J7 



V/V\, 



I. 



11. 



in. 



IV. 



V. 



Id 























0*0 



0-838 



0316 



0-300 



0-318 



0-289 



0-8 



0-592 



0-561 



0-539 



0-560 



0-520 



0'7 



0-780 



0-7M 



0-780 



0750 



0-720 



or. 



0*01] 



0-894 



0-879 



0-880 



0-882 



o:> 



1 (II 10 



1000 



11)00 



1 000 



1 000 



1 



1-055 



i-080 









0-8 



10S7 











0'2 



1101 











According i«> Llutherford's theory the helium atom contains 

 two electrons. Since helium is a monatomio gas this gives 

 n = 2 as for hydrogen. Experiments on dispersion in helium 

 give pas 5 1 92 . L0 1B . Introducing these values lor n and v in 

 (20) wo get values for ./• which are a little greater than those 

 for hydrogen. The theoretical ratio between the ranges in 

 helium and in hydrogen is L'09. The measurements of E. P. 

 Adams' *, disoussed in the Eormer paper, were in disagree- 

 ment with the calculation that the range in helium was 

 shorter than in hydrogen ; the ratio between the ranges 

 observed being only 0*87. Taylor's recent measurements, 

 however, give for this ratio 1/05, in (dose agreement with 



the theoretical value. 



For air Marsden and Taylor f have recently made an 



accurate determination of the velocity curve. They found 

 thai, a. rays I Vom radium C will travel through .">' , . ) ."> em. of 

 air at, l. r >° and 7(Jt) mm. pressure before their velocity is 



reduced to |V . Cf wo assume thai t he nit rOgen atom con- 

 tains 7 electrons and the oxygen atom 8 eleotrons, we get 

 for the air molecule in mean //—Ml. 1 nt roducing t his in 

 the formula (20) and putting flJi = 5*$*5 for V = JV , we find 



l«,o- r =5*37 and 2 log v- 38*32. The values for x/aii cor- 

 responding to this value for log Zq are given in the column II. 

 of the table. Not so many values are given as lor hydrogen, 

 since the fulfilment of the conditions mentioned in section L, 

 on accouni of the higher frequencies, claims greater values 

 for V for air than for hydrogen. Column [V. contains the 

 values for x)x\ observed by Blarsden and Taylor. The 

 agreement between th< i calculated and the observed values 



is very close. At the same time it will he seen that the 



values in column [V. differ considerably from those in 



* Physical Review, sxiv. p. L18 (1007), 



t Proc. Hoy, Soc, \. Lxxxviii. p. I !■"> (1918). 



