54 ORIGIN AND NATURE OF LIFE 



language the one spectrum is the negative 

 of the other. The connecting link is found 

 when the light from such a source as a gas 

 burner is sent through hot sodium vapour, 

 for now a spectrum is obtained identical with 

 the solar spectrum so far as these two sodium 

 lines are concerned. The two lines now 

 show up black like two fine ink lines, in an 

 otherwise continuous spectrum. 



The conclusion is inevitable. From the 

 white-hot central part of the sun called the 

 photosphere, which would yield a continuous 

 spectrum, the light passes through an upper 

 zone or chromosphere which contains volati- 

 lized sodium. By exactly similar reasoning 

 and experimentation the vapour or chromo- 

 sphere of the sun between the internal white- 

 hot mass and our earth has been shown to 

 contain a large number of our terrestrial 

 elements, some of them in a partially evolved 

 form as proto-elements. 



This is the simple basis of stellar chemistry, 

 and for some years now many other suns 

 than the centre of our planetary system have 

 been carefully charted as to their spectra, 

 and classified as to their temperature and 

 chemistry. Terrestrial chemistry has learnt 

 much from these terrifically hot furnaces 

 set in the heavens, giving human observa- 



