204 THE NEW KNOWLEDGE. 



ance in the spark. Turning to the sun, we find that the 

 lines characteristic of the flame spectrum do not appear, 

 while some of the spark lines do. Magnesium, therefore, 

 takes its place beside iron as an element which, in the sun, 

 exists in a dissociated form; or, at any rate, that is the 

 only explanation which will render the results consistent 

 with reason. 



THE CASE OF CALCIUM. 



The evidence of dissociation in the sun afforded by cal- 

 cium is interesting. In the electric-arc spectrum of cal- 

 cium, a certain blue line is particularly prominent, while 

 two other lines, named H and K respectively, are thin. 

 In the solar spectrum, on the other hand, the H and K 

 lines of calcium are particularly thick, while the blue line 

 is thin. Again, in solar storms the blue line of calcium is 

 always absent, while the H and K lines of the element are 

 almost always seen. Still again, the blue line is absent in 

 eclipses, while the H and K lines are the brightest seen or 

 photographed. Finally, in photographing the spectra of 

 sun-spots it was discovered that the H and K lines of 

 calcium are reversed or darkened, while the blue line is 

 not reversed. It must be obvious, then, from this evidence 

 that the calcium which on earth yields all three lines, must 

 in the sun be decomposed into at least two sub-substances, 

 one of which is in causal connection with the blue line 

 and the other with the H and K lines. 



STELLAR EVIDENCE. 



But evidence is found in other suns. The spectra of 

 the stars afford in many cases the same simplified spectra 

 observed in the sun, of iron, magnesium and calcium. In 

 addition, simplified spectra of other metals are discovered, 

 such as titanium, copper, manganese, nickel, chromium, 



