CH. xv.] CONSTITUTION OF ATOM 149 



the jelly, with a force directed to that centre, and 

 varying as the direct distance from it. 



This hypothesis, in spite of obvious weaknesses con- 

 nected with the nature of the positive unit, has great 

 attractiveness : for it explains the constant period 

 of an orbit ; it can explain the occurrence of visible 

 radiation by perturbations of the orbit during 

 collision ; and it has been shown by J. J. Thomson 

 to be capable of carrying us a long way towards a 

 rational electrical theory of Mendele*efFs series of 

 the chemical elements, together with some of their 

 chemical especially their electro-chemical proper- 

 ties, and some features of their spectra. Moreover 

 it goes further and explains in a fairly natural 

 manner, and without artificiality, the gradual degra- 

 dation of atomic energy by slow uncompensated 

 and unperceived radiation ; the consequent gradual 

 oncoming of instability ; and the occasional cata- 

 clysmic transmutation of one element into another, 

 or rather into others, with explosive violence, as 

 observed in the facts of radio-activity. It gives in 

 fact a rational though preliminary view of the 

 hypothetical evolution of all matter, which many 

 known circumstances now tend to support; and it 

 accounts in a kinetic fashion for the immense store 

 of intra-atomic energy. Nevertheless it is very far 

 from being an established theory, and another view 

 that can be taken of the rest of the atom is : 



(4) That it consists of a kind of interlocked 

 admixture of positive and negative electricity, 

 indivisible and inseparable into units, and incapable 

 of being appreciably sheared by applied forces, but 

 incorporated together as a continuous mass ; in the 

 midst of which one or more isolated and indi- 

 vidualised electrons may move about and carry on 



