of nitrogen in a strong magnetic field. 355 



in the red, orange and yellow almost disappear, whilst those in 

 the green, blue and violet become brighter and stronger, and this 

 is especially noticeable in the bands in the blue parts of the 

 spectrum. But there did not appear to be any shift of the bands 

 either relatively to each other or to their respective previous 

 positions. Nor did there appear to be any widening or division 

 of the separate lines forming the bands. Particular attention was 

 devoted to the three strong lines which form the " heads" of the 

 bands, and which are much easier to observe in consequence of 

 their great intensity as compared with the other lines. But no 

 widening nor separation could be seen in any of them. The 

 apparent widening may be explained by the increased intensi- 

 fication in the luminosity of the separate constituents of the 

 bands in the green, blue and violet regions, when the discharge 

 is taking place in the magnetic field. 



These experiments, therefore, confirm the previous observa- 

 tions. And whatever be the origin of the vibrations which 

 produce the nitrogen bands, they seem to prove that these 

 vibrations are different from those produced in the spark spectra 

 of elements, whose lines, in a magnetic field of the same strength, 

 are not only widened but are separated into several constituents. 



