Electromagnetic Theory: Volume 3

PREFACE TO VOL. III.

Long ago I had the intention, if circumstances were favourable, of finishing the third vohinie of this work about 1904, and the fourth about 1910. But circumstances have not been favourable. That is all that need be said about it here, save to add that I have excluded parts of the third volume, and included parts of the fourth.

It would be as wrong to love your enemies as to hate your friends. Nevertheless, '' the way of life is wonderful; it is by renunciation." Especially when prodding is no longer necessary. If my life is spared, I hope to be able to present a bust of the eminent electrician who invented everything worth mentioning to the Institution over which he once ruled, to

be placed under that of Faraday.

Oliver Heaviside.

August 23, 1912.
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CHAPTER IX.

WAVES FEOM MOVING SOURCES.

Adagio. Andante. Allegro moderato.

§ 450. The following story is true. There was a little boy, and his father said, ** Do try to be like other people. Don't frown." And he tried and tried, but could not. So his father beat him with a strap; and then he was eaten up by lions.

Reader, if young, take warning by his sad life and death. For though it may be an honour to be different from other people, if Carlyle's dictum about the 30 millions be still true, yet other people do not like it. So, if you are different, you had better hide it, and pretend to be solemn and wooden-headed. Until you make your fortune. For most wooden-headed people worship money; and, really, I do not see what else they can do. In particular, if you are going to write a book, remember the wooden-headed. So be rigorous; that will cover a multitude of sins. And do not frown.

There is a time for all things : for shouting, for gentle speaking, for silence ; for the washing of pots and the writing of books. Let now the pots go black, and set to work. It is hard to make a beginning, but it must be done.

Electric and magnetic force. May they live for ever, and never be forgot, if only to remind us that the science of electromagnetics, in spite of the abstract nature of the theory, involving quantities whose nature is entirely unknown at present, is really and truly founded upon the observation of real Newtonian forces, electric and magnetic respectively. I VOL. m. B



cannot appreciate much the objection that they are not forces; because they are the forces per unit electric and magnetic pole. All the same, however, I think Dr. Fleming's recent proposal that electric force and magnetic force shall be called the voltivity and the gaussivity a very good one ; not as substitutes for with abolition of the old terms, but as alternatives; and beg to recommend their use if found useful, even though I see no reason for giving up my own use of electric and magnetic force until they become too antiquated.

Having thus got to the electric and magnetic forces, it is only a short step farther to near the end of the book— namely, to the simple cases in which they occur simultaneously. It does not follow that the matter which comes towards the end of a treatise—for instance. Maxwell's great work—is harder than that in the first chapter of his Vol. I. On the contrary, some parts of it are easier out of all comparison. In the course of the next generation many treatises on electromagnetics will probably be written; and there is no reason whatever (and much good reason against it) why the old-fashioned way of beginning with electrostatics (unrelated to the general theory) should be followed. After all, should not the easier parts of a subject come first, to help the reader and widen his mind ? I think it would be perfectly practical to begin the serious development of the theory with electro-magnetic waves of the easy kind. First of all, of course, there should be a good experimental knowledge all round, not necessarily very deep. Then, considering the structure of a purely theoretical work to co-ordinate the ...