160 THE CHEMISTRY OF THE SUN. [CHAP. xn. 



the spectrum of the metallic element itself consists of lines, the 

 number and thickness of some of which increase with increased 

 quantity, the spectrum of the compound consists in the main of 

 flutings and bands, which increase in like manner. 



In short, the molecules of a simple body and a compound one 

 are affected in the same manner by an increase in their quantity 

 in so far as their spectra are concerned ; in other words, both 

 spectra have their long and short lines, the lines in the spectrum 

 of the element being represented in the spectrum of the com- 

 pound by bands or fluted lines ; and in each case the greatest 

 simplicity of the spectrum depends upon the smallest quantity, 

 and the greatest complexity upon the greatest. 



The heat required to act upon such a compound as a salt of 

 calcium, so as to render its spectrum visible, dissociates the com- 

 pound according to its volatility ; the number of true metallic 

 lines which thus appear is a measure of the quantity of the 

 metal resulting from the dissociation, and as the metal lines 

 increase in number, the compound bands thin out. 



