338 Mr. R. S. Hutton on the 



of current flowing through the spark. This conclusion is in 

 gratifying agreement with the work of Trowbridge and 

 .Richards *, who have similarly used the damping effect upon 

 an oscillatory current to measure the resistance, but have done 

 this by direct substitution. 



3. It appears from Table IV. that when the secondary circuit 

 is closed by a spark, the primary current decreases with the 

 length of this spark ; but the secondary current decidedly 

 increases. This behaviour is not explained by the approxi- 

 mate theory here deduced, but was most unmistakable both 

 in early preliminary work and in the later more careful deter- 

 minations here recorded. It still remains to be shown whether 

 this is due to the conditions of the experiment, or is to be 

 explained by a more accurate application of theoretical 

 reasoning. 



In conclusion, it only remains for me to express my thanks 

 to Professor A. G. Webster for his unfailing sympathy and 

 helpfulness, which has rendered this work possible, and to 

 Clark University which placed at my disposal the facilities for 

 the work. 



XXXI. Compound Line- Spectrum of Hydrogen. 

 By R. S. Hutton, B.Sc.i 



1. Introduction. 



HP HE general conclusion arrived at by spectroscopists with 

 -*- regard to the compound line-spectrum of hydrogen is 

 that it really belongs to the element, and not to a hydro- 

 carbon as was at one time supposed. Nevertheless the question 

 cannot be said to be absolutely proved, especially in view of 

 Cornu's experiments, which seemed to indicate that if the 

 vacuum-tubes have been previously washed out with oxygen, 

 the compound line-spectrum disappears, or at any rate becomes 

 much weakened. It seemed to me to be of utility to repeat 

 Corim'sif experiments in a different form, and also to prepare 

 the hydrogen by methods different from those in common use. 



2. Fractionation of the Hydrogen occluded by Palladium. 



It first occurred to me that good results might be expected 

 by carefully fractionating off the hydrogen absorbed by 

 palladium § ; and although my attention was shortly after 



* Phil Mag. (5) xliii. pp. 349-367 (1897). 



t Communicated bv Arthur Schuster. 



% A. Cornu, Journ.de Phys. ii. 5. pp. 100-103 & 341-354 (1886). 



§ I was able to make use of this method by the great liberality of 

 Messrs. Matthey in lending me 50 grams of palladium-foil, gratitude for 

 which I wish to express here. 



