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Map III. — Comparison of metallic lines with, lines of cleveite gases in stars of 

 increasing temperature. 



It will be seen from the map that there is a perfect continuity both 

 in the case of the metallic and the cleveite gas lines, and that in 

 those stars where the separate investigations of the metallic and gas 

 lines overlap, the same arrangement of stars results in both cases, 

 but there is a complete inversion in the behaviour of the gas as compared' 

 with the metallic lines. We seem to be in presence of a chemical 

 change, iron being finally replaced by helium. 



Hydrogen. 



The dark lines of hydrogen make their appearance in stars of 

 comparatively low temperature, such as x Orionis, iu which the 

 second stage metallic lines are very strong. In these stars the 

 hydrogen lines are thinner than some of the metallic ones. 



