244 THE CHEMISTRY OF THE SUN. [CHAP. 



line increases until the temperature of the flame rises high enough 

 to fuse the platinum, and thus put an end to the experiment." 



It is remarkable that in the case of this body which goes 

 through its changes at relatively low temperature, its compounds 

 are broken up at the temperature of the Bunsen burner. Thus 

 the spectrum of the chloride, so far as I know, has never been 

 recorded. 



Stellar Evidence. 



I propose now to return to the case of calcium and see how 

 the views put forward on solar and terrestrial evidence are 

 borne out by the facts which are presented to us by the stars. 

 There is no need to occupy much space in this, in fact reference 

 need only be made to Dr. Huggins's paper which was communi- 

 cated to the Eoyal Society in 1880, and with that paper we 

 may compare some earlier writings. It was as early as 1864 

 that Dr. Huggins, who was then associated with the late 

 Prof. Miller, called attention to the strong lines of hydrogen 

 visible in the spectra of the hottest stars. 1 In this paper 

 it was pointed out at the same time that other metallic lines 

 associated with those lines of hydrogen were thin and faint. It 

 has been already mentioned that, as we have independent 

 evidence that these stars are hotter than our sun, we had strong 

 grounds for believing that here we were in presence of a result 

 brought about by a higher temperature, associated as it was 

 with a simpler spectrum, and, therefore, presumably with simpler 

 constituents. 



We need not stop now to discuss the objection which has been 

 put forward by an ingenious person ignorant of the facts, that 

 the broadening of these lines may not be due to an increase of 

 temperature at all, but really to a very rapid equatorial rotation 

 of the star. This is a fair sample of one of the classes of 

 objections one has to meet. Of course it is at once put out of 



1 "On the Spectra of some of the Fixed Stars," Proc. Roy. Soc. 1864, p. 242. 



