In my previous post, The Point-atoms of Ruđer Josip Bošković: The Key to the Fields of Michael Faraday, I wrote that I intend to write about the replacement of the electrodynamics of Wilhelm Eduard Weber with that of James Clerk Maxwell. In this post, I will show how he, in the Preface to the First Edition of his A Treatise on Electricity and Magnetism,1 wrote explicitly on the subject of action-at-a-distance versus propagation of forces through Faraday’s fields.
Clerk Maxwell begins by acknowledging the great advances in electrical science conducted by first Carl Gauss, then Weber and colleagues, mainly in Germany, all presupposing action-at-a-distance. If I am not mistaken, the “J. and C. Neumann” should read “F. and C. Neumann”, and so the enumerated scientists then would be Carl Friedrich Gauss, Wilhelm Eduard Weber, Bernhard Riemann, Franz Ernst Neumann, his son Carl Gottfried Neumann, and the Dane Ludvig Lorentin Lorenz.
Great progress has been made in electrical science, chiefly in Germany, by cultivators of the theory of action at a distance. The valuable electrical measurements of W. Weber are interpreted by him according to this theory, and the electromagnetic speculation which was originated by Gauss, and carried on by Weber, Riemann, J. and C. Neumann, Lorenz, &c., is founded on the theory of action at a distance, but depending either directly on the relative velocity of the particles, or on the gradual propagation of something, whether potential or force, from the one particle to the other. The great success which these eminent men have attained in the application of mathematics to electrical phenomena, gives, as is natural, additional weight to their theoretical speculations, so that those who, as students of electricity, turn to them as the greatest authorities in mathematical electricity, would probably imbibe, along with their mathematical methods, their physical hypotheses. [p.x]
However, Clerk Maxwell makes it clear that he cannot accept the principle of action-at-a-distance, and that his treatise will demonstrate that the use of the electric and magnetic fields have the same, if not better, explanatory power.
These physical hypotheses, however, are entirely alien from the way of looking at things which I adopt, and one object which I have in view is that some of those who wish to study electricity may, by reading this treatise, come to see that there is another way of treating the subject, which is no less fitted to explain the phenomena, and which, though in some parts it may appear less definite, corresponds, as I think, more faithfully with our actual knowledge, both in what it affirms and in what it leaves undecided.
He does acknowledge that the two methods should be compared, however, he also makes it clear that in no way is he playing judge, but, rather, an advocate for one side.
In a philosophical point of view, moreover, it is exceedingly important that two methods should be compared, both of which have succeeded in explaining the principal electromagnetic phenomena, and both of which have attempted to explain the propagation of light as an electromagnetic phenomenon and have actually calculated its velocity, while at the same time the fundamental conceptions of what actually takes place, as well as most of the secondary conceptions of the quantities concerned, are radically different.
I have therefore taken the part of an advocate rather than that of a judge, and have rather exemplified one method than attempted to give an impartial description of both. I have no doubt that the method which I have called the German one will also find its supporters, and will be expounded with a skill worthy of its ingenuity. [pp.x-xi]
To better understand these issues, we will have to go back to the arguments of the seventeenth and eighteenth centuries, starting with Galileo, Descartes, Huygens, Newton and Leibniz.
James Clerk Maxwell. A Treatise on Electricity and Magnetism, vol.1. Dover, 1954. Unabridged, slightly altered, republication of the third edition, published by the Clarendon Press in 1891.
Hi John Plaice,
I tag along because I have an inner interest in these subjects. But tag is all I can do. I don't have the chops to really understand what is written here. Or what was written by those of yesteryear. Though I have tried.
Please keep writing, it is deeply appreciated. Though I see through a glass most dimly.