Electromagnetic Theory

Abstract

THE basis of Mr. Heaviside's treatise is the inter-linked magnetic and electric circuits. This is taken from Maxwell, but it is much more fully developed, and the analogy between the electric and magnetic circuits is followed out with great care, and is insisted upon at every turn. That you can have a conductor charged electrically, while you cannot have a single magnetic pole, destroys the perfection of the analogy but little. There is a more serious hiatus in the absence of the magnetic analogue to an electric conductor. Mr. Heaviside, however, completes the analogy by imagining such things as magnetic conductors and magnetic currents. The magnetic displacement and convection currents of course exist, but magnetic conduction current, with its corresponding magnetic conductivity, is a most useful notion. The ideas of the magnetic current must not be confused with the unscientific notions of magnetomotive force and magnetic resistance, which are supposed to bring electromagnetism within the intellectual reach of the benighted practical man. At first Mr. Heaviside uses the hypothetical magnetic current as a means of giving his readers a thorough grasp of the interlinked circuits, and of completing the analogy between them. Later, however, in dealing with submarine messages, he shows that magnetic conductivity outside the wires, which is easy to treat mathematically, would have the same effect on the messages as electric resistance in the cable itself, which would be more difficult.

Electromagnetic Theory.

By Oliver Heaviside Vol. I. (London: The Electrician Printing and Publishing Company, Limited, 1893.)