On the Chemistry of the Hottest Stars. 



165 





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Map I. — Behaviour of metallic lines in stars of increasing temperature. 



Iron. 



Starting with a Orionis, we find that only two of its more promi- 

 nent lines may coincide with enhanced lines in the region compared. 

 As there are so many lines in the spectrum of this star, it is possible 

 that these may be only chance coincidences, and this is the more 

 probable since the lines which are most enhanced are certainly 

 absent. Further, I have already shown* that "the temperature of 

 the most important iron-absorbing region in a Orionis is nearer that 

 of the oxy-coal-gas flame than that of the electric arc ; it is probable 

 that the average temperature is intermediate between that of the arc 

 and that of the flame, but nearer to the latter." 



In a Orionis then we have iron represented by low temperature lines 

 corresponding to a temperature intermediate between the first and 

 second stages. 



* ' Phil. Trans.,' 1893, vol. 184, A, p. 703. 



N 2 



