ON THE OKIGIN OF THE PLANETARY SYSTEM. 155 



and 9 represent small portions of the solar spectrum 

 as mapped by Kirchoff, taken from the green, yellow, 

 and golden-yellow, in which the chemical symbols 

 below Fe (iron), Ca (calcium), Na (sodium), Pb (lead) 

 and the affixed lines, indicate the positions in which 

 the vapours of these metals, when made incandescent, 

 either in the flames or in the electrical spark, would 



FIG. 9. 



show bright lines. The numbers above them show 

 how far these fractions of Kirchhoff's map of the whole 

 system are apart from each other. Here, also, we see 

 a predominance of iron lines. In the whole spectrum 

 Kirchhoff found not less than 450. 



It follows from this, that the solar atmosphere con- 

 tains an abundance of the vapours of iron, which, by 

 the way, justifies us in concluding what an enormously 

 high temperature must prevail there. It shows, more- 



