686 Prof. R. W. Wood on Resonance Spectra of 



weak. This is due to the fact that we have a different 

 distribution of intensity in the mercury exciting lines in the 

 two cases. The wave-lengths given in the following table 

 are determined from plates made with the Cooper-Hewitt 

 lamp. Values starred were from plates made with the prism 

 spectrograph. 



Series excited by the two Yellow Mercury Lines. 



6547 * 



6540-2* 



6472 * 



6466-4* 



6388-4* 



6384 * 



6306*5* 



6299-5* 



622453 



6219-84 



6147-30 



6143 



Missing 



5993-28 



5988-21 



5918-90 



5914-02 



5846-36 



5841-29 



5769-60 Hg 



75 



78-6 



82 



82 



77-2 

 77 



74-4 

 72-5 

 76-7 



6659-2 

 f 6578-0 

 16571-7 



6487-5 



6481-0 



64060 



6404-2 



6327-8 



6324-6 



6342-93 



6240-24 

 f 6163-62 

 \ 615340 



6092 * 

 / 6086-5* 

 (6083 * 



6010 * 



5931-24 



5865 



5790-66 Hg 



81-2 



80-5 



81-5 



78-2 



84-9 



80 



77 



76-5 



79 



66-2 

 74-3 



The wave-length differences are not as regular as in the 

 case of the series excited by the green line, and there is no 

 point in calculating the reciprocals or frequencies in this 

 case. 



The distances between the components of the doublets 

 excited by the more refrangible of the two yellow lines varies 

 from 4*5 to 7 Angstrom units, which in itself indicates that 

 the series spacing cannot be uniform. 



The series excited by the yellow line of longer wave-length 

 is still more lawless ! Some lines are single, some double, 

 and one triple. 



Structure of the Lines under High Resolving Power, 

 Multiplex Excitation. 



If we examine under high resolving power the series of 

 doublets excited by the green mercury line, we find a 

 remarkably complicated structure which appears to result 

 from the circumstance that we are dealing with multiplex 

 excitation. The spectra were photographed with a concave 

 grating of six-foot radius, ruled with 15,000 lines to the inch. 

 The iodine tube was excited by the Cooper-Hewitt lamp, and 



