on the Intensity of spectrum lines 49 



It may be of interest to note that in solar spectroscopy the 

 spectrum of the sunspots is found to difTer in many respects from 

 that of the photosphere, considerable numbers of enhanced lines 

 occurring in the sunspot spectrum. The existence of a powerful 

 magnetic field in sunspots has been demonstrated by the Zeeman 

 effect and possibly the differences in the spectrum of the sunspot 

 and the photosphere may be attributed to this new effect of the 

 magnetic field on the spectrum. 



The further study of this effect and the examination of other 

 spectra are in progress. 



Cavendish Laboratory, 

 Cambridge. 



VOL. XX. PART I. 



