110 INORGANIC EVOLUTION. [CHAP. 



feeble one, and nothing came of them. In 1885 M. Fievez* was more 

 fortunate. He made a set of experiments which may be said to be the 

 first recorded success, or at least partial success, of the solution of this 

 problem which now concerns us. M. Fievez observing with a flame in 

 a magnetic field as Faraday had previously done. He noticed a widen- 

 ing, and apparently a doubling of lines, but the doubling he attributed 

 to absorption. He wrote : 



" Les phenomenes qui se manifestent sous Faction du magnetisme 

 sont identiquement les memes que ceux produits par une elevation de 

 temperature." 



In spite of this, however, Dr. Preston has expressed the opinion 

 that if Fievez " had known the theory, the whole question would have 

 been settled in 1885." 



The subject remained unfruitful until 1897, when Dr. Zeeman 

 made known the results! of an important series of observations which 

 he had been quietly carrying out. 



In a course of measurements concerning the phenomena first ob- 

 served by Dr. Kerr, Dr. Zeeman was led to reopen the inquiry whether 

 the light of a flame submitted to the action of magnetism really did 

 undergo any change. He remarked : "If a Faraday thought of the 

 possibility of the above-mentioned relation, perhaps it might yet be 

 worth while to try the experiment again with the excellent auxiliaries 

 of spectroscopy of the present time. . . ." And his observations 

 established that the bright lines of spectra are modified considerably 

 when a strong magnetic field is used. It was at once seen why pre- 

 vious experimenters had failed : the effect is small, so that besides a 

 strong field, high dispersion is necessary. 



No sooner had Dr. Zeeman made his discovery public, than Pro- 

 fessor Lorentz, and subsequently Dr. Larmor, investigated the subject 

 theoretically. They showed that dealing with the theory in its simplest 

 form, not only mere broadening of the lines should be expected, but 

 that each line should really consist of three separate lines, or in other 

 words, form a triplet. 



According to the simple theory, each element of matter which 

 carries an electric charge proper to it the complex being called an 

 ion has its movements affected by the magnetic field. 



If we consider these ions to be the elements of matter the move- 

 ments of which produce light, it is certain that in a magnetic field the 

 movements will be affected ; there will not only be the normal move- 

 ment in the orbit, but an added precessional movement, or spin, round 



* Bulletin de VAcad. des Sciences de Belgique, 3e Serie, tome ix, p. 381, 1885. 

 t Phil. Mag., [5], vol. xliii, p. 226. 



