2 ' 
n? = A =- ——__— 
A —? in 
in which 2,, the wavelength of the ultraviolet free vibration, is 
taken to be 0,087 u”), the following values have been calculated 
for e/m: 
2 in uu efm AO for HE (85 ker 9.5) 
589 ded 
405 18 
oils 1.51 
265 13° 
248 1.56 
235 1267" 
The increase here found for e/m does not accord with the assump- 
tion of a single ultraviolet free vibration. 
I must, in conclusion, offer my warmest thanks to Prof. Dr. H. 
KAMERLINGH ONNES for inviting me to undertake this investigation 
and for placing the necessary high-pressure apparatus at my disposal 
and also to Prof. Dr. L. H. Smrrsema for granting such excellent 
facilities for the work and for the unflagging interest with which he 
has followed the investigation. 
Delft, October 1912. Physical Laboratory of the 
Technical University. 
1) SIERTSEMA and DE Haas. These Proc. Vol. XIV. p. 603. 
(December 30, 1912). 
