srxvn.] SEPARATIONS SUGGESTED. 387 



Spectra of titanium, nickel, and manganese in which the lines were not all 

 produced at the two poles, some occupying an intermediate position : the lines 

 thus arranging themselves en echelon along the spectrum. 



Photographs showing the separation of lines in mixtures. 



Spectrum of lithium containing impurity lines of calcium, strontium, iron, and 

 manganese ; the calcium and manganese lines cling to one pole, and the iron 

 and strontium lines to the other. 



Different parts of iron spectrum, showing calcium lines starting from one pole, 

 and iron lines from the other. 



Photographs showing similar separation of lines in the spectrum of the 



same substance. 



Spectrum of copper showing that this separation can exist not only between 

 two metals, but even between lines of the same metal. In this the blue calcium 

 line is also seen thickened at the upper pole, while the H and K lines were only 

 seen at the lower pole. 



Photographs of spectra showing thickening in the centre of the arc in 

 the case of some lines only. 



Strontium, containing two lines, one, barium, showing very little thickening, 

 while the other true strontium line exists only at the centre as a broad, fluffy 

 reversed line. , 



Copper : all the copper lines in this photograph have their central portions ex- 

 panded, and most of them to a greater extent on the less than on the more 

 refrangible side. Some of the iron lines have also their centres expanded, which 

 is not the case with the calcium lines, those lines in the blue being developed at 

 their extremities. 



Magnesium, showing line in the blue-green, with a central expansion on the 

 less refrangible side, giving the line the appearance of a half spindle, b being 

 quite normal. 



Photographs showing thickening of different lines at different levels. 



Spectra of copper and nickel, showing the irregular thickening of different lines 

 at different levels of the arc. 



It will be gathered from the observations recorded, that the 

 bright lines seen with the naked arc, concur with the line 

 reversals seen under like conditions, in showing such pheno- 

 mena as would certainly be produced by separations if separa- 

 tions were effected. This is abundantly demonstrated by the 

 fact that the lines of the same metal behave in exactly the 

 same way as the lines of different metals do when mixtures of 

 metals are rendered incandescent. 



c c 2 



