On the Recent Theories of Electricity. 197 



a physical problem, as if. is incapable of verification by 

 experience. This does not mean that such questions should 

 not be discussed, but the method of their discussion and the 

 results obtained are properly the method and results of 

 metaphysics and are not in the category of physical phe- 

 nomena and laws. 



As the purpose of this article is to show that we may 

 retain the idea of the mechanical nature and invariable 

 inertia of matter, and at the same time account for the 

 electromagnetic momentum and other properties of elec- 

 trified matter by considering electricity as an attribute of 

 matter rather than the converse, it is convenient to state 

 and discuss a few postulates beforehand which bear on the 

 subject. 



We shall assume length, mass, and time to be the funda- 

 mental units of measure. These quantities and their deriL 

 vatives are continuous or, at least, indefinitely divisible. 

 The continuity of space and time is generally accepted ; 

 without this belief it is impossible to establish the geometrical 

 laws founded on the point, line, and surface or the analytical 

 laws of the calculus. But the divisibility of matter is not 

 usually supposed to be infinite. Indeed, the denial of this 

 assertion is the foundation of all atomic theories. Yet it is 

 difficult to see how mathematics can be anything but abstract 

 logic, or how it can be applied to physical problems unless 

 this third fundamental quantity, which is as it were the con- 

 necting link between the abstract and the concrete, be al>o 

 indefinitely divisible. How, otherwise, can we replace finite 

 bodies by mathematical centres of inertia? In this con- 

 nexion Professor Sir Joseph Larmor * says : a The difficulty 

 of imagining a definite uniform limit of divisibility of matter 

 will always be a philosophical obstacle to an atomic theory, 

 so long as atoms are regarded as discrete particles moving 

 in empty space. But as soon as we take the next step in 

 physical development, that of ceasing to regard space as 

 mere empty geometrical continuity, the atomic constitution 

 of matter (each ultimate atom consisting of parts which are 

 incapable of separate existence, as Lucretius held) is raised 

 to a natural and necessary consequence of the new stand- 

 point." This is clearly an attempt to reconcile the two 

 incommensurable antinomies of continuity and discontinuity, 

 which are usually attached to the names of Descartes and 

 Lucretius. This Sir J. Larmor tries to do by postulating 

 the existence of a true matter, which is a continuous plenum 

 and imperceptible to our senses, and relegating sensible 



* ' .Ether and Matter,' p. 76. 



