( 99 ) 



currents assumed in the ionic theory of magnetism ^), favour the 

 circular vibrations more than those along the lines of force ^). If 

 this be assumed we are also compelled to admit that the revolving 

 of the ions takes place more in a given direction than in the 

 contrary. Hence then there must be a difference of intensity between 

 the two outer components of the triplet and between the two com- 

 ponents of the doublet. Although the ordinary magnetism of the 

 highly-magnetic substances has probably disappeared in the spark, 

 it seems rather natural to examine in the first place iron, nickel 

 and cobalt in search of a phenomenon in which the „molecular cur- 

 rents" of Ampère (or that part of these currents, which is pro- 

 duced by the motion of the light-ions) would manifest themselves 

 optically. However it seems to me by no means decided beforehand, 

 that other substances would not exhibit something of this kind. I 

 have however investigated in the first place iron. 



The first results obtained were much promising. In the field used 

 several of the iron lines exhibited on the negatives a more intense 

 component at the less refrangible side of the spectrum. Further 

 inquiry has however shown that this seemingly positive result seems 

 to be of no value. I will give the results of my experiments 

 only in extract. Before describing them, it may be remarked, that, 

 if a directing influence, as mentioned, exists, we must expect that 

 the component at the less refrangible side must be intensified and 

 in the case of the triplet as well as in that of the doublet. The 

 sign of the charge of the ions cannot have any influence upon 

 this result. 



2. Negatives were taken in the spectra of the third and second 

 orders obtained by means of a Rowland grating (radius 10 ft., 

 14438 lines to the inch). More accurately was studied the part of 

 the spectrum between 3000 and 4000 A. U., when viewed in the 

 two principal directions iicross and along the lines of force. The vast 

 majority of the iron lines were, with the field used, resolved into 

 doublets, triplets, quartets etc. perhaps only three or four lines seemed 

 unaffected. Now I found in the case of a few lines inequality between 

 the outer components of a triplet across and of the corresponding 



1) cf. KicHAEz. Wied. Aan. 58, p. 385, 41U. 1894. 



2) cf. LoRENTZ. "Versl. Ak. Amsterdam, October '97, p. 213. [It was pointed out 

 by LoEENTZ in the article referred to, tbat the phenomena observed by EaoROFFand 

 Georgieavsky can be explained, without any hypotliesis of the kind mentioned by 

 the absorption, which the rays from the posterior ])art of the flame undergo in the 

 interior part.] 



7 



Proceediugs Royal Acad. Amsterdam. Vol. I. 



