2 he Grating Spectrum of Radium EmanatL 



203 



Three photographs were obtained, two being o£ the end-on 

 discharge seen through a quartz window in the end of the 

 tube ; in the latter cases it was not possible to remove the 

 hydrogen completely by a preliminary heating of the tube 

 for fear of cracking the quartz-glass joint. The photographs 

 were measured up by means of a Kayser's measuring machine 

 with a pitch of ^ mm. 



About 35 of the more intense lines previously obtained by 

 Rutherford and Royds * with a glass prism can be seen on 

 the photographs together with four additional lines farther 

 in the ultraviolet. The new lines W 4631*89, 4628*08 near 

 the intense line X 4625*58 are only seen in one photograph 

 (which had the longest exposure), but they may have been 

 hidden in the prism photographs by the broadening of the 

 intense line due to overexposure ; the lines W 4572*66, 

 4568*24 are only seen in the same photograph. The spectrum 

 presents the same characteristics as those previously obtained, 

 the relative intensities being those of photograph 3 of the 

 former paper rather than those of photograph 2. 



The wave-lengths of the spectrum obtained by means of 

 the grating are given in the accompanying list. The error 



Wave-lengths of the Emanation Lines. 



X 





\ 



x 





\ 



(Grating). 



Intensity. 



(Prism). 



1 (Grating). 



Intensity. 



(Prism). 



5084-45 



1 



5084-5 



4568-24 



2 



not observed 



497902 



3 



4979-0 



1 4508-68 



7 



45090 



4861-55 



10 



(4861-49 Hj3) 



1 4503-89 



2 



4504-0 



4828-46 



1 



4827-8 ' 



4439-88 



1 



4440-0 



4817-33 



5 



48172 



4435-25 



3 



4435-7 



4796-73 



1 



4796-7 



437170 



1 



43721 



4768-16 



5 



47679 



4349-81 



15 



4350-3 



4721-70 



2 



4721-5 



1 434069 



4 



(434066 Hy) 



4701-88 



3 



4701-7 



4203-39 



10 



4203-7 



4680-92 



10 



4681-1 



' 4166-59 



20 



4166-6 



4671-58 



1 



46718 



4114-71 



6 



4114-9 



4644-29 



15 



4(144 7 



j 4017-90 



6 



40180 



4(534-13 



3 



(4634-15 H) 



3981-83 



15 



3982-0 



4631-89 



2 



not observed 



3971-71 



8 



3971-9 



4628-08 



1 



not observed 



395730 



8 



3957-5 



4625-58 



15 



4625-9 



! 3664-96 



5 



3(564-6 



4609-40 



10 



4609-9 



3612-76 



3 



3612-2 



4604-46 



6 



4604-7 



312202 









458003 



3 



(4580-1 H) 



3100-31 



1 





457777 



8 



4578-7 



3089-15 









4572-66 







not observed ! 



1 



3005-84 



1 





Rutherford aud Royds, Phil. Mag. Aug. 1908. 



