4:66 Prof. McLennan and Mr. Ireton on Fundamental 





Series 



Spectra. 







1*5, S — m, p 2 series. 





Mercury. 



Zinc. 





Cadmium. 



m 



2536-72 



3076-99 





3260-17 



2 



1435-59 



1632-08 





] 71 0-58 



3 



1307-83 



1468-90 





1537-89 



4 



1259-31 



1408-86 





1474-06 



5 



1235-91 



1379-38 





1442-60 



6 



1222-44 



1362-59 





1424-40 



7 



1213-97 













8 



Lt 11880 1320-0 1378-7 



1\5, S — m, P series. 



Vlercury. 



Zinc. 



Cadmium. 



771. 



1849-6 



2139-33 



228879 



2 



1402-71 



1589-64 



1669-3 



3 



1268-9 



1457-64 



1526-73 



4 



1250-6 



1376-97 



1469-35 



5 



Lt 1188-0 1320-0 13787 a 



To work in this direction some experiments were set on 

 foot by McLennan and Ainslie with a fluorite spectrograph, 

 and others by McLennan and Lang with a vacuum grating 

 spectrograph. It was found that with both instruments 

 much time was consumed in working out technical details. 

 The results obtained to date with them will be published 

 shortly, and they will show that with the fluorite spectro- 

 graph it is now easy to obtain spectrograms down to 

 \— 1400A.U. With the vacuum grating spectrograph 

 spectrograms well below X, = 600 A. U. can be readily 

 obtained. 



IV. Fundamental Series. 



From the experiments described above it will be seen that 

 it is possible with the vapours of mercury, zinc, and cadmium 

 to stimulate at will the radiation — and this radiation only — 

 given by the first member of the combination series 

 j/=(P5 5 S) — (2, p 2 ). It is also possible to cause the atoms 

 of the same vapours at will to emit the radiation given by 



