1 heory of the Chemical Elements. 865 



in the radioactive elements, and it will be seen that a con- 

 sistent- scheme for these transformations can be founded 

 upon the views advocated in the paper — a scheme which 

 readily removes many of the outstanding difficulties. It 

 has not been possible, for reasons of space, to treat these 

 elements at all completely in the paper ; but sufficient 

 indications of this point have been given, and the subject 

 will be treated in greater detail later. 



Elements which appear out of their places in the Periodic 

 System always appear to need a characteristic construction 

 of a somewhat different type from that of the class of 

 elements with which they are associated, and with which 

 the chemist is unable to find a clear connexion. It may 

 be said that exactly in proportion as a set of elements do 

 form a real chemical class, it has been found possible, as 

 the result of an exhaustive examination, to endow the set 

 with constitutions of a similar nature. Moreover, with 

 elements for which the chemical determination of the atomic 

 weight has been carried out to the second decimal place, 

 it has been possible only in a few cases to find a choice of 

 formulae which would yield this value equally well. 



It is perhaps necessary to point out at once to what extent 

 the paper is speculative. This character must largely belong 

 to it because the subject is treated only from the point of 

 view of atomic weight. But the results are capable of 

 verification in other ways, some of which are indicated. 

 In particular, the actual existence of the primary substances 

 has been verified by a mathematical investigation of their 

 spectra, to be published independently, which shows that 

 they are the origin of the unknown lines in the spectra of 

 the nebulae and of the solar corona. 



The acceptance of these results involves secondary con- 

 sequences of a far-reaching kind. In the first place, the 

 nature of the positive electricity in the atom is determined, 

 and found to he that supposed by Sir J. J. Thomson in his 

 paper of 1904*. That is to say, positive electricity is re- 

 garded as existing in uniform volume distributions, whose 

 volume is proportional to the positive charge. But in the 

 conception of the structure of a simple atom there is a 

 difference. Sir J. J. Thomson treated the electrons in the 

 atom as revolving inside the positive sphere, which was of 

 atomic size. On the view developed in this paper, positive 

 electricity exists in units very small in radius compared even 

 with the electrons, and is the source of nearly the whole mass 

 of the atom. The revolving system is therefore a planetary 

 * Phil. Mao;. March 1004. 



