Michael Faraday, His Life and Work

by Silvanus P. Thompson

The paper on the “Physical Character of the Lines of Magnetic Force” recapitulated the points established in the twenty-ninth series of “Researches,” and emphasis is laid upon the logical necessity that time must be required for their propagation. The physical effects in a magnetic field, as equivalent to a tendency for the magnetic lines to shorten themselves, and to repel one another laterally, are considered, and are contrasted with the effects of parallel electric currents. Commenting on the mutual relation between the directions of an electric current and of its surrounding magnetic lines, he raises the question whether or not they consist in a state of tension of the æther. “Again and again,” he says, “the idea of an electrotonic state has been forced on my mind. Such a state would coincide and become identified with that which would then constitute the physical lines of magnetic force.” Then he traces out the analogy between a magnet, with its “sphondyloid” (or spindle-form field) of magnetic lines, and a voltaic battery immersed in water, with its re-entrant lines of flow of circulating current. Incidentally, while discussing the principle of the magnetic circuit, he points out that when a magnet is furnished at its poles with masses of soft iron, it can both receive and retain a higher magnetic charge than it does without them, “for these masses carry on the physical lines of force, and deliver them to a body of surrounding space, which is either widened, and therefore increased, in the direction across the lines of force, or shortened in that direction parallel to them, or both; and both are circumstances which facilitate the conduction from pole to pole.”

NOVELTY OF FARADAY’S VIEWS.

Thus closed, with the exception of two fragmentary papers, one on “Physical Lines of Force,” and the other on “Some Points in Magnetic Philosophy,” in the years 1853 and 1854 respectively, the main life-work of Faraday, his “Experimental Researches.” Their effect in revolutionising electric science, if slow, was yet sure. Though the principle of the dynamo was discovered and published in 1831, nearly forty years elapsed before electric-lighting machinery became a commercial product. Though the dependence of inductive actions, both electromagnetic and electrostatic, upon the properties of the intervening medium was demonstrated and elaborated in these “Researches,” electricians for many years continued to propound theories which ignored this fundamental fact. French and German writers continued to publish treatises based on the ancient doctrines of action at a distance, and of imaginary electric and magnetic fluids. Von Boltzmann, a typical German of the first rank in science, says that until there came straight from England the counter-doctrines amidst which Faraday had lived, “we (in Germany and France) had all more or less imbibed with our mothers’ milk the ideas of magnetic and electric fluids acting direct at a distance.” And again, “The theory of Maxwell”—that is, Faraday’s theory thrown by Maxwell into mathematical shape—“is so diametrically opposed to the ideas which have become customary to us, that we must first cast behind us all our previous views of the nature and operation of electric forces before we can enter into its portals.” The divergence of view between Faraday and the Continental electricians is nowhere more clearly stated than by Faraday’s great interpreter, Maxwell, in the apologia which he prefixed in 1873 to his “Treatise on Electricity and Magnetism,” wherein, speaking of the differences between this work and those recently published in Germany, he wrote:—

One reason of this is that before I began the study of electricity I resolved to read no mathematics on the subject till I had first read through Faraday’s “Experimental Researches on Electricity.” I was aware that there was supposed to be a difference between Faraday’s way of conceiving phenomena and that of the mathematicians. So that neither he nor they were satisfied with each other’s language. I had also the conviction that this discrepancy did not arise from either party being wrong. I was first convinced of this by Sir William Thomson [Lord Kelvin], to whose advice and assistance, as well as to his published papers, I owe most of what I have learned on this subject.

As I proceeded with the study of Faraday, I perceived that his method of conceiving the phenomena was also a mathematical one, though not exhibited in the conventional form of mathematical symbols. I also found that these methods were capable of being expressed in the ordinary mathematical forms, and thus compared with those of the professed mathematicians.

For instance, Faraday, in his mind’s eye, saw lines of force traversing all space where the mathematicians saw centres of force attracting at a distance. Faraday saw a medium where they saw nothing but distance. Faraday sought the seat of the phenomena in real actions going on in the medium; they were satisfied that they had found it in a power of action at a distance impressed on electric fluids.

When I had translated what I considered to be Faraday’s ideas into a mathematical form, I found that in general the results of the two methods coincided, so that the same phenomena were accounted for and the same laws of action deduced by both methods, but that Faraday’s methods resembled those in which we begin with the whole and arrive at the parts by analysis, while the ordinary mathematical methods were founded on the principle of beginning with the parts and building up the whole by synthesis.

I found, also, that several of the most fertile methods of research discovered by the mathematicians could be expressed much better in terms of ideas derived from Faraday than in their original form.

The whole theory, for instance, of potential, considered as a quantity which satisfies a certain partial differential equation, belongs essentially to the method which I have called of Faraday....

If by anything I have here written I may assist any student in understanding Faraday’s modes of thought and expression, I shall regard it as the accomplishment of one of my principal aims: to communicate to others the same delight which I have found myself in reading Faraday’s “Researches.”