88 Dr. W. N. Hartley on the 



The lines which appear as if common to the iron and the 

 platinum-spectrum, namely, 2627*9 and 2625'2 in Liveing 

 and Dewar's spark-spectrum of iron, are both very strong in 

 the arc as well as in the . spark. They are seen in the 

 spectrum of pure platinum equal in strength to the lines in 

 the brittle platinum, but not so strong as in the iron. Two 

 lines, apparently the same, appear nearly as strong in the 

 rhodium-spectrum as in that of iron. Taking Exner and 

 Haschek's spectra of the platinum metals as a guide (K. Akad. 

 der Wissenschaft, Wien, Druckschriften, Mittheilung vi. 

 1897), but disregarding the measurements in Mittheilung i. 

 1895, which are inaccurate, we have the following measure- 

 ments closely approximating to those just mentioned. 



Platinum. 



Palladium. 



Rhodium. 



2628-13 



2628-38 



2628-34 



2625-41 





2625-55 



As Exner and Haschek's photographs were not taken in 

 such a manner as to show any marked features in the lines, I 

 availed myself of a series of photographs taken by Dr. Adeney 

 with the Rowland spectrometer in the Royal University of 

 Ireland, which he kindly allowed me to examine. The charac- 

 teristic features of the lines are the same as those seen on the 

 photographs taken from prism spectra, already mentioned as 

 having been published in the Transactions of the Chemical 

 Society in 1882. They can therefore be identified with 

 comparative ease, and when they differ in character it may 

 safely be concluded that they are different lines. Both lines 

 in the iron-spectrum are common to the arc and spark, and 

 they have the same intensity. Liveing & Dewar's numbers 

 differ from those of Kayser and Runge, and also from the 

 later and more exact measurements made by Kayser (Ann. 

 der Physik, ser. 4, vol. iii. 1900) which for these lines are 

 given below. 



Wave-lengths. Character. 



2628383 Thin in the middle but broad at 



each end. 

 2625*754 The same but the ends are broader. 



EHODIUM LINES r 262834 The same as the iron lines. 



(Exner & Haschek) (.2625*55 



(2628*13 Of the same thickness throughout, 



weak compared with the iron 

 lines, but stronger than the more 

 refrangible platinum line. 



2625*41 Thin in the middle, nearly dis 



continuous, but thicker at either 

 end. A weaker line than the 

 one less refrangible. 



IRON LINES 



(Kayser) 



PLATINUM LINES 



(Exner & Haschek) 



