XIV.] OBJECTIONS TO THE DISSOCIATION HYPOTHESIS. 123 



chemical conditionings, as revealed by spectra, of these masses must be 

 preceded by an inquiry into the distribution of the visible masses, con- 

 sidered merely as masses, and quite independent of chemistry. 



We must therefore first deal with the general distribution of the 

 stars and nebulae, independently of their chemistry. That will give us 

 a general idea of our stellar system. 



Having this as a basis, we can next see whether stars of the same 

 chemistry are seen along the same radius (taking our solar system as 

 the centre) or the same direction in space. Next, taking distances into 

 account, we can see if there be any proof of different chemical shells, 

 so to speak. 



It must be borne in mind that a greater or less proportion of stars of 

 the same chemical quality in certain regions will not touch the question. 

 We can only deal with demonstrations of the absence of certain 

 chemical elements in certain regions, so far as the stars supply us with 

 evidence. 



