874 
canal-rays of hydrogen, helium and lithium. In his experiments 
the electric field, €, reached values of more than 150 electrostatic 
units, viz. €,, in electromagnetic units was more than 45 kilovolt/em; 
the largest separation surpassed 2 uu for H7, (A = 434,1 uw). 
Starting from the theoretical equivalence of €, and the vector- 
product [BH] W. Wien‘) then presumed an analogous specific 
magnetic separation of spectral lines of hydrogen canal-rays 
and experimentally verified this. In his experiments the maximum 
velocity in the canal-rays, ®, reached a value of 7700 km. per 
second; while the magnetic field was about 17 kilogauss. The 
separation observed for H, was of the order of 0,5 uu, i.e. very 
much larger than that ef the ordinary Zeeman-effect, for which the 
normal separation in this field would amount to about 0,03 uu only. 
As far as we can now already judge, we have here two separate, 
without doubt closely connected, phenomena, which are both propor- 
tional with the field and which appear to depend on the velocity of 
the charges. With an extremely sensitive method PascHENn and GurLacu 
sought for an electric effect (€ = 15 kilovolt/em) in mercury vapour; 
but in vain. From this they rightly conclude, that there is no 
question here of an electric analogon of the real Zeeman-effect. For 
this is generally shown by many lines of emission, absorption 
and fluorescence of vapours and selective crystals : the unsensitiveness 
of certain lines moreover may be only apparent (dà < 0,002 uu 
say). 
As early as 1899 this problem was treated theoretically by Voter’); 
according to him an electro-optic displacement or separation probably 
would occur, though maybe a very small one, proportional with 4° €?. 
Therefore it would be favourable for observation to choose these two 
factors as large as possible. Recently, before the publication of 
Wien’s experiments however, WARBURG and ScHWARZSCHILD *) have 
developed formulae, the former starting from the theory of quanta, the 
latter by means of purely attractory considerations. SCHWARZSCHILD 
d. Phys. 43 p. 965—1045, 1914; Phys. Ztschr. 15 pp. 215, 265, 1914; Verh. D. 
Phys. Ges. 16 p, 304, 1914. Elektr. Spektr. anal. chem. Atome, Leipzig 1914. A. 
Lo Surpo, Rend. Acc. Lincei (1) 23 p. 143, 1914; Phys. Ztschr. 15 p. 122, 
1914. H. .Wisar, Gött. Nachr. 9 p. 20, 1914. H. Lunetunp, Ann d. Phys. 45. 
p. 517, 1914. 
1), W. Wien, Sitz. Ber. Berl. Akad. 48 p. 70, 1914. 
2) W. Vorer, Wied: Ann. 69 p. 297, 1899; Ann. d. Phys. 4 p. J97, 1900; 
Arch. Néerl. (2) 5 p. 366, 1901. Magneto- und Elektrooptik pp. 357, 380, Leipzig 
1908 ; Gött. Nachr. 9 p. 1, 1914; Ann. d. Phys. 45 p. 461, 1914. 
5) EK. Warpure, Verh. D. Phys. Ges. 15 p. 1259, 1913. K. ScHWARZSCHILD, 
ibidem 16 p. 20, 1914. 
