226 THE CHEMISTRY OF THE SUN. [CHAP. 



Thus the two lines H and K (3933 and 3968), assigned both to 

 iron and calcium by Angstrom, were traced to calcium by the 

 following observations : f 



a. The lines are well represented in the spectrum of com- 

 mercial wrought iron, but are absolutely coincident with two 

 thick lines in the spectrum of calcium chloride with which the 

 iron spectrum has been confronted. 



&. The lines are represented by mere traces in the spectrum 

 of a specimen of pure iron prepared by the late Dr. 



FIG. 85. Diagram showing the process by which impurities are eliminated 

 from spectra. The lines marked - are due to impurities of one substance in 

 another ; those marked + are not due to impurities and are therefore common 

 lines. 



Matthiessen, and obligingly placed at my disposal by Dr. 

 Eussell. Both poles of the lamp were of iron, the lower 

 pole consisting of an ingot of the metal which had been 

 cast in a lime-mould. 



c. The lines are altogether absent from a photograph of pure 

 iron, where both poles of the lamp were of the pure metal not 

 cast in lime, and they are likewise absent in a photograph of 

 the spectrum of the Lenarto meteorite. 



