610 Drs. Geiger and Kovarik on Relative Number of Ion* 



atmospheric pressure and temperature and per atom breaking 

 up is 



1-39 xlO" 1 



= G-44xlO- 8 E.S.U. 



1-44 xl0 5 x 15 



Taking the charge of an electron as 4*65 x 10" 10 E.S.U., 

 this corresponds to a production of loS ions per cm. of path 

 in air. 



4. 



5. 



7- I 



Substance. 



S «2 



Current per /3 Particle. 



Number of 

 Ions pro- 

 duced in 

 first cm. 

 of path. 



Whole 



number 



of 1 ons 



produced. 



Electr. I. 

 (Hemi- 

 sphere,) 



Electr. II. 

 (12-7 cm. 3 ) 



Electr. III. 



(3-84 cm/') 



Average 

 Value. 



Actinium ... 



28-5 



6-4 Xl0~ 8 



6-4xl0" 8 



6-lxlO" 8 



6*3 XlO" 8 



136 



100 XlO 3 



Thorium D ... 



163 



63 „ 



6'2 „ 



6 3 „ 



63 „ 



136 



17-3 „ 



Radium B 



750 



63 „ 



6-1 ., 



61 „ 



6-2 „ 



133 



37 „ 



Radium C 



135 



to 

 50 



48 „ 



5-0 „ 



5-1 n 



50 „ 



108 



77 „ 



Radium E 



433 



31 „ 



33 „ 



3-2 „ 



32 „ 



69 



33 „ 



Uranium 



144 



35 „ j 3'6 „ 





3'6 „ 



78 



11-3 „ 





Thorium A ... 130 





20 x 10- 8 











Radioactin'um. ! 175 





0-7 „ 











Actinium A ... 1*25 















Radium D 120 





0-5 „ 











The results obtained for the different substances are 

 collected in the table above. Columns 3, 4, and 5 give the 

 values of the currents due to the /3 rays for the first centi- 

 metre of path and per atom breaking up, column 6 the 

 mean value, weight being given according to the number of 

 experiments performed with each electroscope. From these 

 values the number of ions produced by a /3 particle per cm. 

 are deduced and entered in column 7. From this figure the 

 whole number of ions produced by a ft particle over its 

 entire path can be found by integrating over the absorption 

 curve. The figures thus obtained are entered in column 8. 



We shall first discuss the figures given in the uprer part 



