Historical research guide · 0952 · 1855

Michael Faraday — Experimental Researches in Electricity (lines of force)

Michael Faraday

In one minute

Faraday spent twenty years turning an invisible thing into something he could count. In 1831, in the first series of these researches, he noticed that a wire sitting inside a changing magnetic influence is not in its ordinary condition at all — it is under a kind of tension, before any current flows — and he named that the electro-tonic state. Twenty years later, in the twenty-eighth series read to the Royal Society in 1851, he defined a line of magnetic force exactly, and showed by experiment that the amount of force crossing any slice of a bundle of those lines is the same at every slice, inside the magnet as well as out in the air. Then, in a June 1852 paper he deliberately published as speculation rather than as a Philosophical Transactions result, he asked whether those lines physically exist in the space between magnets — and answered that he thinks they do, and that whatever constitutes them is the same electro-tonic state he had glimpsed in 1831.

Connection

Chapter 10 is built on the vector potential, and this is where the vector potential comes from: Maxwell took Faraday’s electro-tonic state and wrote it as the quantity we now call A, which is the thing Aharonov and Bohm later showed a shielded electron can feel. Chapter 1 gets the model for how a claim climbs the ladder — Faraday states the measured part as fact, labels the speculative part as speculation on the same page, and names the measurement that would decide it.

From the source

A line of magnetic force may be defined as that line which is described by a very small magnetic needle when it is moved along its own length so that the needle stays tangent to the path; or as that line along which a transverse wire may be moved in either direction with no tendency to form any current in it, while motion in any other direction does produce such a tendency.Series XXVIII, paragraph 3071
The lines represent a determinate and unchanging amount of force: the sum of power contained in any one section of a given portion of the lines is exactly equal to the sum of power in any other section of the same lines, however altered in form, and however convergent or divergent they may be at the second place — and this holds inside the magnet as well as outside it.Series XXVIII, paragraphs 3073, 3109 and 3121
Whilst a wire is subject to either volta-electric or magneto-electric induction it appears to be in a peculiar state, resisting the formation of a current that would otherwise be produced, and able to originate a current when left uninfluenced — an electrical condition of matter not hitherto recognised, which Faraday named the electro-tonic state.Series I, section 3, paragraph 60
The lines of magnetic force incline Faraday to the opinion that they have a physical existence correspondent to that of their analogue, the electric lines; and again and again the idea of an electro-tonic state has been forced on his mind, a state which would coincide with, and become identified with, that which constitutes the physical lines of magnetic force.On the physical character of the lines of magnetic force, paragraph 3269
The current developed in a wire moved across the lines cannot have its entire foundation in the mere fact of motion; there must be a previous state, a state of tension or a static state as regards the wire, which, when motion is superadded, produces the dynamic state or current of electricity.On the physical character of the lines of magnetic force, paragraph 3270
There is one question in relation to gravity which, if we could ascertain or touch it, would greatly enlighten us — whether gravitation requires time; if it did, it would show undeniably that a physical agency exists in the course of the line of force.On the physical character of the lines of magnetic force, paragraph 3246

The way in

https://www.gutenberg.org/ebooks/14986

Historical source-access record. This guide links to the original; it does not reproduce the paper text.

PUBLICATION. Experimental Researches in Electricity was issued in three volumes: volume 1 in 1839 (Richard and John Edward Taylor, London), volume 2 in 1844, volume 3 in 1855 (Richard Taylor and William Francis). The registry identifier 18391855 is the span of the three volumes, not a book number. Faraday numbered every paragraph of the whole work in one unbroken sequence from 1 to 3430, and those paragraph numbers — not pages — are the locators used throughout this page and throughout the literature. PUBLIC DOMAIN. The work is out of copyright everywhere by age; Michael Faraday died on 25 August 1867. It may be read, copied and reproduced freely. WHAT WAS READ, 2026-09-08. Volume 1 was read from the Project Gutenberg edition, ebook 14986, prepared from the Bibliothèque nationale de France Gallica images — that is the source of paragraph 60 below. Volume 3 was read from the Internet Archive scan of the 1855 first edition, identifier experimentalres04faragoog — that is the source of Series XXVIII, read to the Royal Society on 27 November and 11 December 1851 and printed in the Philosophical Transactions for 1852, and of the paper On the physical character of the lines of magnetic force, which Faraday published in the Philosophical Magazine for June 1852 and signed at the Royal Institution on 6 March 1852. WHAT IS REPRODUCED. Selected paragraphs only, chosen for the argument this site teaches from; the complete three volumes run to well over half a million words and are free at both sources. Nothing is paraphrased inside the passages — where a paragraph is given, it is given whole. TEXT REPAIRS. Both files are optical character readings of nineteenth-century typesetting. Long-s and ligature damage has been repaired, running heads, signature marks and the scanner’s own Digitized by Google interruptions removed, and Faraday’s italics rendered as emphasis. Two specific repairs are worth naming: the Gutenberg transcription of paragraph 60 prints the coined term as electro-ionic, which is a transcription error — Faraday’s word, used everywhere else in the same section and reused by him at paragraph 3269, is electro-tonic, and it is given correctly here; and the volume 3 scan renders phaenomena inconsistently, which is normalised. Cross-references in parentheses are Faraday’s own paragraph pointers and are left as he wrote them. RELATED PAGES on this site: the vector potential that Maxwell built directly out of Faraday’s electro-tonic state runs through Aharonov and Bohm’s 1959 paper at /library/stm-6ec95a6893, Tonomura’s electron-holography confirmation at /library/stm-bc13f9b9e6 and the completely shielded 1986 experiment at /library/stm-d084b3d3cb; Whittaker’s two potential-function papers of 1903 and 1904 are at /library/stm-b69d1c5209 and /library/stm-db53a69c6c; and Terence Barrett’s Topological Foundations of Electromagnetism, which extends Maxwell theory along the same line, is at /library/stm-b373bceb75.

How to cite it

Michael Faraday (1855) Michael Faraday — Experimental Researches in Electricity (lines of force) https://www.gutenberg.org/ebooks/14986

Where it sits in the curriculum

Scalar waves and the field behind the fields