188 



INORGANIC EVOLUTION. 



[CHAP. 



[This table shows the effect for the three lines which form the first natural 

 triplet in the spectrum of cadmium compared with the corresponding lines in the 

 spectrum of zinc and magnesium. It will be seen that the corresponding lines in 

 the different spectra suffer the same magnetic effect both in character and magni- 

 tude. Thus the corresponding lines 4800, 4722, 5173 are each resolved into 

 sextets, and the rate at which the ionic orbit is caused to precess is the same for 

 each (denoted by ejm = 87 in the table). Similarly for the other corresponding 

 lines.] 



This is a result of the first order of importance. I previously dis- 

 cussed what might be expected to happ3n if the complex system 

 giving the spectrum of an element were broken up, and showed that if 

 less complex systems of the same pattern that is, consisting of centre 

 of force and ion with its electric charge were thus produced, these 

 systems would be just as capable of giving spectra as the one the 

 breaking up of which produced them. We should get new ions free to 

 move 'and vibrate, and new spectra which may reveal the constituents, 

 that is, the mariner in which the complex system breaks up. But 

 Dr. Preston goes further that this. He shows that the same ion 

 associated with different centres of force gives us lines at different 

 wave-lengths. That a certain ion which in the spectrum of mag- 

 nesium gives rise to b is also present in zinc and cadmium, though 

 there is no trace of b in their spectra. 



Now, if the views held by those who have worked along any of 

 these lines be confirmed, we shall be compelled not only to give up 

 polymerisation as the only cause of greater complexity of the mole- 

 cules of the elements, but to acknowledge a great strengthening of the 

 view that all chemical atoms have a common basis, and build new 

 mental images on this basis. I now pass from the spectroscopic 

 evidence to work in a new field. 



Professor J. J. Thomson's Researches. 



I have before referred to the fact that science now has to consider 

 masses much smaller than the atom of hydrogen. This we owe not 

 only to a discussion of the phenomena of series, but also to some 



