640 Scientific Intelligence. 



the preceding results involve simultaneously the vibrations paral- 

 lel and perpendicular to the magnetic field. At 32430 gauss, 

 when the perpendicular vibrations alone were photographed, 

 the two diffuse wisps remained while the central sharp component 

 was absent. Also, at 32000 gauss, when only the parallel vibra- 

 tions were transmitted, the two lateral wisps disappeared abso- 

 lutely but the central, resultant line remained sharp and intense. 

 Thus, the original triplet has been reduced to a single line which 

 is completely polarized. It is, therefore, evident that the impor- 

 tant discovery of Paschen and Back consists in showing that the 

 anomalous Zeeman effect exhibited by close doublets and triplets 

 can be reduced to the normal type by using sufficiently strong 

 magnetic fields. Of great theoretical moment is likewise the fact 

 that the polorization becomes complete. 



In a later paper A. Sommerfeld has discussed mathematically 

 a hypothetical model which accounts for most, but not all, of the 

 phenomena observed by Paschen and Back. Instead of consider- 

 ing the electromagnetic behavior of a single electron which is 

 bound to its position of rest in an isotropic manner (Lorentz), 

 Sommerfeld imagines a quasi elastic anisotropic bonding for the 

 electron. He also assumes that the three corresponding fre- 

 quencies, n l3 n^ n 9 , are not very different in value. The last 

 hypothesis conforms to the cases of close doublets and triplets. 

 It is then shown that the anisotropic electron will approach 

 asymptotically a condition in which it will behave, with respect 

 to its mean frequency of vibration, precisely like the usual iso- 

 tropic electron, as the magnetic field is increased in strength. — 

 Ann. d. Phys., No. 15, 1912, p. 897; No. 4, 1913, p. 748. 



h. s. u. 



7. The Spectrum of 'Helium Canal Rays. — It has been shown by 

 J. J. Thomson that helium ions may be present in the canal rays 

 which have one and also two positive charges due to the loss 

 respectively of one and two electrons. The problem of the con- 

 nection between these singly and doubly charged ions and the 

 spectral series of helium has been successfully investigated by J. 

 Stark, A. Fischer and H. Kirschbaum. Since the argument is 

 long and involved it will not be possible to reproduce it in this 

 place. It may be stated, however, that the authors found it 

 necessary to study the Doppler effect, not only in pure helium, 

 but also in helium mixed with iodine and with oxygen. The 

 most important conclusions are the following : The principal 

 series and the two subordinate series of doublets of helium have 

 as carriers the positive, singly charged ions, while the principal 

 series and the two subordinate series of simple lines have the 

 positive, doubly charged helium ions as carriers. The series of 

 single lines were formerly ascribed by Runge and Paschen to a 

 hypothetical element which they called "parhelium." Although 

 this gas does not exist in the chemical sense of an element which 

 can be isolated, it is interesting to note that its spectrum has 

 been accounted for in a perfectly satisfactory manner. — Ann. d. 

 Phys., No. 3, 1913, p. 499. h. s. u. 



