158 THE CHEMISTRY OF THE SUN. [CHAP. 



which differentiated the elements already traced in the sun from 

 those not traced ; lists were prepared showing broadly the chief 

 chemical characteristics of the elements traced and not traced. 

 This was done by taking a number of the best known com- 

 pounds of each element (such, for instance, as those formed 

 with oxygen, sulphur, chlorine, bromine, or hydrogen), stating 

 after each whether the compounds in question were unstable 

 or stable. Where any compound was known not to exist, that 

 fact was indicated. 



Two tables were thus obtained, one containing the solar, the 

 other the more important non-solar elements (according to our 

 knowledge at the time). 



These tables gave me, as the differentiation sought, the fact 

 that in the main the known solar elements formed stable oxygen- 

 compounds. I have said in the main, because the differen- 

 tiation was not absolute ; but it was sufficiently strong to make 

 me commence operations by searching among the Fraunhofer 

 lines for the longest lines of the outstanding strong oxide- 

 forrning elements. 



The immediate result l was that strontium, cadmium, lead, 

 copper, cerium, and uranium were shown with considerable 

 probability to exist in the solar atmosphere, in addition to the 

 elements in Thalen's last list. 



Certain of those elements which form unstable compounds 

 with oxygen were also sought for; gold, silver, mercury, being 

 examples. None of these were found, however. 



This was in 1874. The total result then was as follows : 



Metals present in the Sun. 



Sodium Cobalt Cadmium 



Iron Hydrogen Lead 



Calcium Manganese Copper 



Magnesium Titanium Cerium 



Chromium Strontium Uranium. 



Nickel 



Proc. Roy. Soc. No. 147, 1873, p. 512. 



