204 Intelligence and Miscellaneous Articles. 



which, however, are congruent. Potassium is similar, while rubi- 

 dium and caesium again have only two secondary series, which are 

 congruent. The congruence, which in the formula of the series 

 expresses itself by identity of the second and third constants for 

 the two series, has the effect that two such congruent series appear 

 as a series of pairs, but in which the difference of vibration of both 

 lines of the pairs is constant for each series, in opposition to the 

 deportment of the chief series. 



The result comes out that this difference of vibration of the 

 pairs of the secondary series is identical for each element with the 

 difference of vibration of the first pair of the principal series n=3* 

 It has further come out that the magnitude of this difference of 

 vibration is connected with the atomic weight ; the difference of 

 vibration is very nearly proportional to the square of the atomic 

 iveight. With lithium no pairs are visible ; this law extended to 

 lithium enables us to calculate from its atomic weight that the 

 difference of possible pairs would be so small that we should pro- 

 bably see the lines double. 



If we compare the spectra of the alkalies with each other, it is 

 most distinctly evident that both the chief series as well as the 

 secondary series extend towards the red side of the spectrum. This 

 is of course just as apparent in the constants A, B, C, which 

 change, in a manner obviously expressed by a law, from one ele- 

 ment to another. It is worthy of mention that the constant B 

 changes very little, and is the same, not only for the alkalies, but, 

 as seems to be the case, for other elements also. 



We consider it premature to try to discover the law according to 

 which the constants vary from one element to another before we 

 have investigated other elements. We hope before long to lay 

 before the Academy our results in reference to the alkaline earths. 



As a further result of our investigations we must mention that, 

 in contradiction to the statements of Lockyer, who considered that 

 he had found the lines of all pair alkalies among those of Fraun- 

 hofer, only sodium is represented in the Sun, and probably also 

 only its chief series. — Sitzungsberichte der Berliner AJcademie,J\me5, 

 1890. 



ON THE ELECTKICAL SEMES FOR FRICTIONAL ELECTRICITY. 

 BY J. SCHIFF. 



The author gives the following series for frictional electricity: — 

 hair skins, smooth glass, wool, ground glass, silk, resins, collodium, 

 steatite. — Beibldtter der PhysiJc, vol. xiv. p. 525. 



