458 WHAT IS THE SUN MADE OF ? 



spectrum a still greener band ; and so on a particular band 

 or bands for each particular metal. 



And this is curious too, viz. that, if two or more metals 

 be consumed in mixture, such as brass a mixture of copper 

 and zinc for example, the prism picks out (so to speak) the 

 rays peculiar to each metal, depositing them in the spectrum 

 duly arranged each of its own peculiar tint, each in its 

 own proper locality. 



So we now, by a course of experiments, have succeeded 

 in obtaining a banded spectrum. The bands of our spectrum, 

 however, are coloured, whereas those of the solar spectrum 

 the bands of Frauenhofer are black. < There can hardly be 

 any connection between the two phenomena,' say you. Wait 

 a while. 



Turn back now to our sodium. It is burning in a plati- 

 num spoon, we will suppose, evolving a vapour ; that vapour 

 Is burning with the yellow light peculiar to sodium. We 

 will now hold that sodium flame in the very track of the 

 yellow rays that have been separated by the triangular prism 

 from white light of the electric lamp. Watch now the result 

 from the spectrum a band of yellow seems to be clean cut 

 out. There is, in place of it, a black band. Now, is this an 

 arbitrary black band, or is it one to be found in the solar 

 spectrum ? Is it one of the Frauenhofer black bands ? Yes, 

 it so happens to be ; and now, so far as the presence of sodium 

 in the sun is concerned, we have our revelation. 



Assume the following case. Assume that the sun is, as 

 quite anciently it was assumed to be, a glowing ball of fire 

 1,384,492 times larger than our earth a seething mass of 

 burning materials. Assume a blazing flame of vapour to sur- 

 round him one constituent being the vapour of sodium. 

 These conditions granted, we at once account for the one 

 particular black sodium line or band of the Frauenhofer scale 

 ^corresponding with sodium ; and we can account for its pre- 

 sence on no other assumption. 



