XVII.] 



DETAILS OF COINCIDENCES. 

 FINAL EEDUCTION TITANIUM. 



235 



Since therefore these lines which were common to two or more 

 spectra could not be traced to impurities, what was their 

 probable origin ? Their number was so great that to attribute 

 them to physical coincidences, and to rest and be thankful 

 accordingly, would have been to take the very pith and marrow 

 out of the science of spectrum analysis, which we have heard 

 so often is based absolutely upon different substances giving 

 us spectra with special lines for each. The matter then was 

 worthy of serious investigation. 



Lines of one kind we could explain, on the hypothesis that 

 the elements are truly elementary, by supposing that in the case, 



