922 Mr. R. Rossi on a Relation between the 



far they are in agreement with the known results on the 

 retardation of a-rays by metals, and with the hypothesis that 

 the loss of energy by the a-particles is due to an ionization 

 of the metallic molecules. But the close similarity in the 

 behaviour of gold and aluminium is not in accordance with 

 this view. 



3. In view of the dissimilarity in the ionization curves of 

 different gases, the agreement in the curves obtained for 

 aluminium and gold is unexpected, and leads to the suspicion 

 that the observed effects may not be due to the metals them- 

 selves, but perhaps to a layer of adsorbed gas in both cases. 

 A further investigation of this question will be undertaken 

 shortly. 



Sloane Laboratory, 



Yale University. 

 August, 1911. 



LXXXVI1T. On a Relation between the Atomic Volumes and 

 the Spectra of Elements. By R. Rossi, ftJ.Sc* 



OF the recent theories explaining the possible origin of 

 series of lines in spectra, the one which most seems to 

 agree with experimental facts is due to Ritzf. 



Ritz considers an electron vibrating in a magnetic field of 

 strength H, the frequency of vibration being 



mc 



e 

 where — is the ratio of the charge to the mass of the 

 mc ° 



electron in electromagnetic units. The field H can be 

 ascribed to elementary molecular magnets in a line, the 

 electron being on their axis, at a distance r from the nearest 

 pole. The field is then expressed by 



H=±/*(i--^n?), 



±fi being the magnetic charge on each pole, I the length of 

 the magnet, supposed to be made up by these elementary 

 magnets. If l = ns, where n is an integer and s the length 

 of an elementary magnet, and if we write r = as we get 



* Communicated by Prof. E. Rutherford, F.R.S. 

 t k Magnetische Atomfelder und Serienspektren,' Ann. derPhysik, xxt. 

 p. 660 (1908). 



