M. A. J. Angstrom's Optical Researches. 333 



which exhibit themselves in spectra of different metals. That 

 by the use of stronger charges, particularly with the metals 

 which melt at high temperatures, such as platinum and iron, 

 other lines may appear, is probable ; I believe, however, that I have 

 omitted none of the more important ones. The simple inspec- 

 tion of the figure shows, however, a great regularity in the distri- 

 bution of the lines ; also, in the case of some metals, a certain 

 tendency to appear in groups. In this manner they show them- 

 selves with lead, particularly in the yellow and blue-violet field ; 

 with zinc in the red and blue; with bismuth several distinct 

 groups are formed. In general, with the more fusible metals 

 the lines seem to spread themselves more/ With mercury and 

 lead the longest go into violet. It is singular that gold and 

 silver have a common line in green ; but besides this, silver has 

 a few common with mercury. 



To all the metals the line n is common ; also the line m in 

 red, although in consequence of its feebleness it is difficult to 

 determine its position with accuracy, seems to be common to all; 

 with mercury, however, I did not see it. Coal gave no lines, 

 except those which were to be found in all spectra. 



7. Wheatstone has observed that when the poles are formed 

 of different metals, the spectrum contains the lines of both. It 

 was therefore interesting to examine whether a compound of the 

 same metals, particularly a chemical one, would also exhibit the 

 lines of both metals, or distinguish itself by the exhibition of 

 new lines. The first was found to be the case. The only differ- 

 ence observed was, that certain lines were absent, or showed 

 themselves with greater difficulty ; but when they appeared, it 

 was always at the same places corresponding to the single metals. 

 It is easy to convince oneself of this when one pole is formed, for 

 example, of Sn 4 Pb. From the side of the spectrum which cor- 

 responds to the chemical compound, lines proceed which belong 

 to both metals, and the position of these lines may be controled 

 by making use of both metals successively for the opposite pole. 



If the metals are combined in other proportions, no difference 

 appears. With Zn Sn the lines in blue were displaced a little 

 towards the violet, but very inconsiderably. This result is so 

 far of interest for the theory, as it shows that the particles of 

 both metals are not united in particular groups, but that each 

 forms distinct centres of oscillation. 



8. It does not seem that the lines peculiar to each metal in the 

 electric spectrum can be due to interference. By interference 

 tinea of sharp outline cannot be produced except when they lie 

 very near each other, otherwise they spread themselves over a 

 larger portion of the spectrum. Through the union of unequal 

 retardations, groups of fine lines may certainly be formed, but 



