a most important constant about which we shall have much to say later. As for “div” and “curl,” they represent mathematical operations of a peculiar sort. At any rate, the reader need not be alarmed at these equations, for it is not necessary that we understand them. Suffice it to say that (2) represents Faraday’s law of induction, while (4) constitutes the hypothetical law postulated by Maxwell in order to ensure symmetry. Prior to Maxwell’s investigations the fourth equation would have been written “
”; hence it is the adjunction of the term
which constitutes the originality of the theory.
From his field equations, Maxwell by purely mathematical means was able to deduce the two additional ones:
where
represents a particular species of mathematical operation. In ordinary language, these last two equations connote that varying electric and magnetic intensities will be propagated through the ether in wave form with a velocity