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The Effect of Magnetism Upon the Spectral 
Lines of Sodium. 
BY HA, STG) DUNSTAN, (Mode ORICE, “AND Ci (Av) KRAUS, 
Dr. P. Zeeman (Phil. Mag. March, 1897,) has announced the 
discovery of an effect of magnetism upon radiation. Analyzing by 
means of a concave grating the light radiated from a sodium flame 
placed between the poles of an electromagnet, he finds that upon 
exciting the magnet, the spectral lines are very decidedly broad- 
ened. Upon cutting off the exciting current the lines regain their 
usual appearance. 
Zeeman also gives a number of other experiments which seem to 
show that the effect is not due simply to changes of pressure in the 
flame but is caused by a real influence of magnetism upon the radi- 
ations emitted. He considers his results to be confirmatory of the 
theory of Lorentz. * 
The discovery considered from a theoretical standpoint is one of 
great importance, in that it establishes another relation between 
Magnetism and light and is in accord with the electromagnetic 
theory. 
The subject, therefore, seemed to the writers to be worthy of 
quantitative investigation, and this paper is for the purpose of giv- 
ing an account of preliminary measurements of the phenomenon. 
METHOD. 
For the purpose of determining the breadths of the spectral lines 
and the distribution of light in the same. the. writers have used 
Michelson’s Interferometer, which succeeds precisely where the 
diffraction grating fails: i. e., in the analysis of a single line or 
Narrow group of lines. 
A full description of the instrument is given below. 
APPARATUS. 
The light under examination was that given off by a bunsen 
flame, colored by a piece of asbestos saturated with NaOH solution 
and wrapped around the top of the bunsen burner. 
Th La Theorie EKlectromagnotique de Maxwell. Leyde 1892. Versuch einer 
isk der electrischen und optischen Erscheinungen in bowegten Korpern.” Leiden 
(77) KAN. UNIV. QUAR., VOL. VI, NO. 2, APRIL, 1897, SERIBS A. 
