carried by the Ions produced by Rontgen Rays. 543 



the correction two vessels were made of the same shape and 

 size, the one precisely similar to that used in these experi- 

 ments with water at the bottom, while the other had the walls 

 covered with shellac varnish, and the water at the bottom was 

 replaced by an aluminium plate of the same area, and at the 

 same distance from the top plate as the upper surface of the 

 water in the other vessel. The aluminium covers for the two 

 vessels were cut from the same sheet of metal. When these 

 vessels were exposed to the Rontgen rays the current through 

 the vessel containing water was to that through the other 

 vessel as 9 to 8. Thus the current passing directly between 

 the plates was 8/9 of the current observed. Applying this 

 correction the mean value of e is equal to 



fx7-3xlO- 10 =6-5xlO- 10 . 



A series of experiments of a similar kind were made, using 

 hydrogen instead of air. The number of ions in this gas was 

 smaller than in the case of air, and the smaller viscosity of 

 hydrogen made the drops fall much faster ; the drops formed 

 without the rays fell so fast, only taking a second or two, 

 that the rate could not be determined with accuracy, nor was 

 it certain that they had reached a steady state. The velocity 

 of the hydrogen ion through hydrogen under unit potential 

 gradient is taken as three times that of air and the coefficient 

 of viscosity as 9*3 x 10 " 5 . 



The results of the experiments are given in the following 

 table : — 



Expansion. 



Temp. 



Current 

 through 

 gas. 



Rate of fall 

 of cloud. 



e 



uncorrected for 



nuclei present 



without rays. 



1-36 

 1-38 

 1-37 

 1-35 



16 

 16 

 17 



17 



•21 

 •127 

 •083 

 •19 



•415 cm. /sec. 



•5 



•83 



•5 



6-3x10-1° 



5-5 



69 



8-0 



Mfif 



m 



6-7 XM> 10 











The value of e for hydrogen has not been corrected in the 

 way that the value of e for air has been by allowing for the 

 part of the cloud formed independently of the rays. Allowing 

 for this the experiments seem to show that the charge on the 

 ion in hydrogen is the same as in air. This result has very 



2P2 



