1917] on The Complexity of the Chemical Elements 123 



particle more different from the hydrogen atom than the atom is 

 from the hydroji-en molecule. 



Positive electricity is thus emphatically not the mere absence of 

 electricity, and any electrical theory of matter purporting to explain 

 matter in terms of electricity does so by the palpable sophistry of 

 calling two fundamentally different things by the same name. The 

 dualis'm remains whether you speak of matter and electricity, or of 

 positive and negative electricity, and the chemist would do well to 

 stick to his conception of matter, until the physicist has got a new 

 name for positive electricity which will not confuse it with the only 

 kind of electricity that can exist apart from matter. 



On the other hand, the theory of the electro-magnetic origin of 

 mass or inertia is a true monism. It tries to explain consistently two 

 things — the inertia of the electron and the inertia of matter— by the 

 same cause. The inertia of the former being accounted for by the 

 well-known electro-magnetic principles of Faraday, by the assumption 

 that the charge on the electron is concentrated into a sphere of 

 appropriate radius ; the 2000-fold greater inertia of the hydrogen ion, 

 for example, can be accounted for by shrinking the sphere to one- 

 two-thousandth of the electronic radius. 



But the electrical dualism remains completely unexplained. Call 

 the electron E and the hydrogen ion H. The facts are that two E's 

 repel one another with the same force and according to the same law 

 as two H's repel each other, or as an H attracts an E. These very 

 remarkable properties of H and E are not explained by the explana- 

 tion of the inertia. Are E and H made up of the same stuff or of 

 two different stuffs ? We do not know, and certainly have no good 

 reason to assume, that matter minus its electrons is made of the same 

 thing as the electron. We have still to reckon with two different 

 things. 



The Chemical Elements not necessarily Homogeneous. 



I pass now to the second and most novel sense in which the 

 elements, or some of them at least, are complex. In their discovery 

 of new radioactive elements, M. and Mme. Curie used radioactivity 

 as a method of chemical analysis precisely as Bunsen and Kirchoff", 

 and later Sir William Crookes, used spectrum analysis to discover 

 caesium and rubidium, and thalUum. The new method yielded at 

 once, from uranium minerals, three new radio-elements, radium, 

 polonium and actinium. According to the theory of Sir Ernest 

 Ptutherford and myself, these elements are intermediate members in 

 a long sequence of changes of the parent element uranium In a 

 mineral the various members of the series must co-exist^ in equi- 

 librium, provided none succeed in escaping from the mineral, in 

 quantities inversely' proportional to their respective rates of change, 

 or directly proportional to their periods of average life. Ptadium 



