loo POPULAR SCIENCE MONTHLY. 



at any place produce a state called electric displacement or ether strain, 

 as we can produce compression or rarefaction in air; and, just as the 

 latter changes are said to be created by mechanical force, so the former 

 is said to be due to electric force. We can not define more clearly the 

 nature of this ether strain or displacement until we know much more 

 about the structure of the ether than we do at present. We can picture 

 to ourselves the operation of compressing air as an approximation of 

 the air molecules, but the difficulty of comprehending the nature of 

 an electric wave arises from the fact that we can not yet definitely 

 resolve the notion of electric strain into any simpler or more familiar 

 ideas. 



We have to be content, therefore, to disguise our present ignorance 

 by the use of some descriptive term, such as electric strain, electro- 

 static strain or ether strain, to describe the directed condition of the 

 space around a body in a state of electrification which is produced by 

 electric force. This electric strain is certainly not of the nature of a 

 compression in the ether, but much more akin to a twist or rotational 

 strain in a solid body. 



For our present purpose it is not so necessary to postulate any 

 particular theory of the ether as it is to possess some consistent hy- 

 pothesis, in terms of which we can describe the phenomena which will 

 concern us. These effects are, as we shall see, partly states of electri- 

 fication on the surface or distributions of electric current in wires or 

 rods, and partly conditions in the space outside them, which we are 

 led to recognize as distributions of electric strain and of an associated 

 effect called magnetic flux. 



We find such a theory at hand at the present time in the electronic 

 theory of electricity, which has now been sufficiently developed and 

 popularized to make it useful as a descriptive hypothesis.* This theory 

 has the great recommendation that it offers a means of abolishing the 

 perplexing dualism of ether and ponderable matter, and gives a definite 

 and, in a sense, objective meaning to the word electricity. In this 

 physical speculation, the chief subject of contemplation is the electron, 

 or ultimate particle of negative electricity, which, when associated in 

 greater or less number with a matrix of some description, forms the 

 atom of ponderable matter. To avoid further hypotliesis, this matrix 

 may be called the co-electron ; and we shall adopt the view that a single 

 chemical atom is a union of a co-electron with a surrounding envelope 

 or group of electrons, one or more of the latter being detachable. 

 We need not stop to speculate on the structure of the atomic core or co- 

 electron, whether it is composed of positive and negative electrons or 



* For a more detailed account of this hypothesis, the reader is referred to 

 an article hy the present writer entitled: 'The Electronic Theory of Electricity,' 

 published in the Popular Science Monthly for May, 1902. 



