CONSTITUTION OP MATTER BECQUEREL. 281 



Maxwell and Hertz have demonstrated that the phenomena of 

 light are nothing more than a particular manifestation of the elec- 

 tromagnetic phenomena such as induction, hertzian waves, etc., which 

 may be produced in the ether. 



Everyone is familiar with the decomposition of white light by a 

 prism resulting in the formation of a spectrum in which the colors 

 spread out as in a rainbow. When the light produced by an incan- 

 descent gas is analyzed with the aid of a spectroscope, the observer 

 sees a number of separate brilliant lines. These emission lines are as a 

 matter of fact images of the slit through which the light passes 

 before falling on the prism which separates the radiations of differ- 

 ent colors. These brilliant lines can be transformed into dark 

 absorption lines when a vapor is traversed by a continuous ray of 

 white light; the black lines then indicate the arrested colors. Dif- 

 ferent bodies in a solid state or in solution likewise show character- 

 istic absorption spectra. 1 



The existence of these emission and absorption spectra, and more 

 generally the fact of all the changes undergone by light waves in a 

 body whether at rest or in movement, shows the intervention of mat- 

 ter in the phenomena of which ether is the seat. In order to explain 

 the reciprocal effect of ether and ponderable matter Lorentz con- 

 ceived the idea that light phenomena had their origin in the move- 

 ments of electric charges inclosed in the atom. A remarkable dis- 

 covery made in 189G by Zeeman added to the strength of Lorentz's 

 views. 



Zeeman discovered that under the action of an intense magnetic 

 field the spectrum lines of a gas are decomposed into several com- 

 ponents, and that these component lines indicate that the movement 

 of the corpuscles is polarized — that is to say, oriented, by a magnet. 



Thus, just as in the case of cathode corpuscles, the corpuscles which 

 produce or absorb light may have their movements modified by a 

 magnet. It is consequent!}' certain that the}^ are electrified. 



In the simplest case, where the lines of force of the magnet are 

 parallel to the luminous line, each line is decomposed into a double 

 ray whose components correspond to two vibratory circular move- 

 ments of the corpuscles in opposite directions. 2 



According to the theory of Lorentz the amount of separation of 

 the components allows the calculation of the ratio of the charge to 

 the mass of the corpuscles, and the direction in which a magnetic 

 field of determined direction displaces the components corresponding 

 to the circular vibrations, indicates the sign of the electric charge 

 effecting the movement. 



1 Experiment : Emission spectrum of an electric arc and absorption spectrum of nitrate 

 of didymium. 



2 Projection of a slide representing Zeeman's effect on several of the iron lines (spark 

 spectrum). 



