Some Properties of the a Rays from Radium. 163 



uncorrected values for different values of m in the following 

 table : — 





Corrected Ratios (as percentages). 



Uncorrected 



No. of Phases. 







m = 10. 



m=20. 



m=50. 



m=100. 



m=200. 



m=500. 



percentages. 



Single phase ... 



6713 



68-32 



69-61 



70-14 



70-42 



70-58 



70-72 



Three phase . . . 



56-70 



58-71 



60-18 



60-69 



60-95 



61-10 



61-24 



Four phase ... 



46-04 



47-87 



49-11 



4955 



49-75 



49-905 



5000 



Six phase 



32-46 



33-82 



34-73 



35-03 



35-19 



35-29 



35-35 



Twelve phase... 



15-60 



17-50 



17-97 



18-13 



18-21 



1826 



18-30 



It is of interest to construct a table showing the differences 

 between the above ratios and the corresponding uncorrected 

 ratio, as a percentage of the latter : — 



Percentage difference from uncorrected ratio. 



No. of Phases. 



10. 



Single phase 5-C76 



Three phase 7*413 



Four phase 7'920 



Six phase 8-176 



Twelve phase ... 14*75 



m = 20. 



w = 50. ! m = \00. m=200. wz = 500. 



3-39 



1-57 



•82 



•42 



•20 



4-13 



1-73 



•90 



•47 



•23 



4*26 



1-78 



•90 



•50 



T9 



4-33 



1-75 



•83 



•45 



•17 



4*37 



1-80 



•93 



•49 



•22 



This table brings out the fact that the percentage correction 

 due to voltage drop on the unloaded machine is practically 

 independent of the number of phases, if the value of m is of 

 the order usually found in good design. 



XIX. Some Properties of the a Rays from Radium. By 

 E. Rutherford, F.R.S., Macdonald Professor of Physics, 

 McGill University, Montreal* . 



THE present paper contains the preliminary results of an 

 investigation made for the purpose of accurately de- 

 termining the velocity and ratio e/moi the a particle expelled 

 from radium. The usual method has been adopted of mea- 

 suring the deflexion of a pencil of homogeneous rays 

 when passed through a magnetic and electric field of known 



* Communicated by the Author. 



M 2 



