42 



DR W. GEOFFREY DUFFIELD ON THE 



and Second Subordinate Series, according to the particular formula which includes all 



its members. 



The Zeeman effect, which has been examined by RUNGE and PASCHEN,* shows 

 distinctive behaviour for certain lines, and should afford additional data for their 

 classification, but unfortunately only one of the lines dealt with in this paper has 

 been investigated by their method. 



Pressure is also effective in bringing to light characteristic differences between 

 groups of lines, and studies of their behaviour as regards displacement, broadening, 

 changes in relative intensity, and reversal have been made with this end in view. 

 For silver this method does not yield such definite results as were obtained for the 

 copper spectrum, but they are nevertheless of considerable assistance in this classifi- 

 cation. 



The following table summarizes the methods of forming series in the silver 

 spectrum : 



Fhough the above table shows great resemblances under pressure between the 



ehaviour of a and c, they differ at 1 atmosphere in the manner in which the 



sorption line is superposed upon the bright line, and the photographs show that 



rings of the two differ greatly in structure ; this difference was to have been 



from the differences shown by them in a magnetic field. No such 



les under pressure were, however, discovered for the corresponding copper 



lines 4022, 4063. 



10. The Band Spectrum under Prmwre.-The prominent feature of these 

 RUNGK and PASCHEN, Astrophys. Journ,' vol. XVI., p. 123 1902 



disappear at almost the same pressure, the 2nd sub-series line has been weakened 

 the non-senes line because its original intensity was greater. 



