Tetravalency of Oxygen. 



237 



-CH 2 





TrivalentX"'=( 

 — CH 2 CH 3 



<W". 

 CH 3 







CH 3 

 CH 2 



•CH 



CH 2 

 X a 





CH 2 



-Ah 



1 

 =0 









1 

 =CH 



-Ah 



— CH 2 







1 

 =C 





CH 3 



i 



Monovalent X' = 

 CH 2 



(CH,)'. 



CH 3 







CH 





II 



CH 





-h 







-CH 





-CH 2 





II 

 CH 3 . 



? 





If at present we cannot press the analogy too close in the 

 alternating valency* of so-called elementary radicals or atoms, 

 especially the non-metallic ones, we are surely not yet pre- 

 pared to abandon formulae which have been of such signal 

 service in the development of organic chemistry, and to 

 abolish the notation because we do not yet know the real 

 meaning either of the marks or valency. But is it too bold 

 a thing for us to look forward to the time when we can 

 similarly deal with an elementary radical, the present pro- 

 visional chemical atom ? At present our notions of valency 

 are chiefly conditioned by the experiments made, and the 

 chemical products constantly being beheld, at about 16° C. and 

 76-centim. mercury pressure. It is, therefore, wonderful 

 and encouraging that we should already have a theory which, 

 on the whole, has such promise for the future. And it is not 

 surprising that, as Clerk Maxwell wittily put it at Belfast, 



Though they seetu to cling together, 



And form " associations " here, 

 Yet soon or late they burst their tether, 



And through the depths of space career. 



Oxford, 7th November, 1887. 



* This theory of an alternating valency, as contrasted with both the 

 " almost any " and the " constant one " theories, not only appears to have 

 some support from the vortex-atom theory but from the periodic law, 

 especially when this is exhibited on Prof. J. Emerson Reynold's plan, as 

 exposed by Dr. Crookes. But I see no sufficient reasons for the septava- 

 lencies. 



