The Sun 



teach us anything very new, there is a large 

 number of others, perhaps two-thirds of the 

 total number, which have necessarily an entirely 

 different origin. Now the first spectroscopists, 

 including Kirchhoff, discovered at an early date 

 that nearly all these other dark lines occupy 

 in the field of the spectroscope the identical 

 position occupied by the bright emission lines 

 of hydrogen and of a certain number of metallic 

 vapours; it has thus been possible to identify 

 490 lines belonging to iron with the same number 

 of dark lines belonging to the solar spectrum. 

 Such a number of coincidences could not be 

 due to accident, and leads us to conclude that 

 the photosphere is surrounded by a cooler 

 absorptive gaseous layer, containing in addi- 

 tion to hydrogen the vapours of numerous 

 elements : sodium, barium, calcium, magnesium, 

 iron, manganese, chromium, cobalt, nickel, zinc, 

 copper, titanium, strontium, etc. That is to say, 

 a great proportion of the materials composing 

 our earth. We have therefore demonstrated 

 the existence of a gaseous layer external to the 

 photosphere, to which astronomers have given 



the name of chromosphere. We shall see, in a 



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