Mémoire sur l'action mutuelle de deux courans électriques, sur celle exise entre un courant électrique et un amiant ou le globe terrestre, et celle de deux aimans l'un sur l'autre. Lus à l'Academie royale des Sciences. (Extrait des Annales de Chimie et de Physique, 15).

Paris: l’Academie royale des Sciences, [1820].

First edition, very rare offprint issue, of Ampère’s “first great memoir on electrodynamics” (DSB). In this memoir Ampère “demonstrated for the first time that two parallel conductors, carrying currents traveling in the same direction, attract each other; conversely, if the currents are traveling in opposite directions, they repel each other” (Sparrow, Milestones, p. 33). “It was the discovery of electromagnetism by Hans Christian Oersted in the spring of 1820 which opened up a whole new world to Ampere and gave him the opportunity to show the full power of his method of discovery. On 4 September 1820 Franqois Arago reported Oersted’s discovery to an astonished and skeptical meeting of the Académie des Sciences. Most of the members literally could not believe their ears; had not the great Coulomb proved to everyone's satisfaction in the 1780's that there could not be any interaction between electricity and magnetism? Ampere's credulity served him well here; he immediately accepted Oersted’s discovery and turned his mind to it. On 18 September he read his first paper on the subject to the Académie; on 25 September and 9 October he continued the account of his discoveries. In these feverish weeks the science of electrodynamics was born” (DSB). Ampere’s two papers appeared in the same volume of the Annales de Chimie et de Physique, but not consecutively (pp. 59-76 & 170-218). The present offprint contains both papers and is separately-paginated. OCLC lists four copies, none in US. ABPC/RBH lists five copies: Sotheby’s New York, 13 December 2002, $9500 (inscribed); Christie’s New York, 10 December 1999, $850; Christie’s, New York, 29 October 1998, $9500 (Norman copy, inscribed); Doerling, 23 November 1983, $186 (disbound); Sotheby’s, 30 October 1978, $1304 (Honeyman copy).

“There is some confusion over the precise nature of Ampère 's first discovery. In the published memoir, "Mémoire sur 1’action mutuelle de deux courants électriques,” he leaped immediately from the existence of electromagnetism to the idea that currents traveling in circles through helices would act like magnets. This may have been suggested to him by consideration of terrestrial magnetism, in which circular currents seemed obvious. Ampère immediately applied his theory to the magnetism of the earth, and the genesis of electrodynamics may, indeed, have been as Ampère stated it. On the other hand, there is an account of the meetings of the Académie des Sciences at which Ampère spoke of his discoveries and presented a somewhat different order of discovery. It would appear that Oersted's discovery suggested to Ampere that two current-carrying wires might affect one another. It was this discovery that he announced to the Académie on 25 September. Since the pattern of magnetic force around a current-carrying wire was circular, it was no great step for Ampère the geometer to visualize the resultant force if the wire were coiled into a helix. The mutual attraction and repulsion of two helices was also announced to the Académie on 25 September. What Ampère had done was to present a new theory of magnetism as electricity in motion …

Ampère’s first great memoir on electrodynamics was almost completely phenomenological, in his sense of the term. In a series of classical and simple experiments, he provided the factual evidence for his contention that magnetism was electricity in motion. He concluded his memoir with nine points that bear repetition here, since they sum up his early work.

  1. Two electric currents attract one another when they move parallel to one another in the same direction; they repel one another when they move parallel but in opposite directions.
  2. It follows that when the metallic wires through which they pass can turn only in parallel planes, each of the two currents tends to swing the other into a position parallel to it and pointing in the same direction.
  3. These attractions and repulsions are absolutely different from the attractions and repulsions of ordinary [static] electricity.
  4. All the phenomena presented by the mutual action of an electric current and a magnet discovered by M. Oersted … are covered by the law of attraction and of repulsion of two electric currents that has just been enunciated, if one admits that a magnet is only a collection of electric currents produced by the action of the particles of steel upon one another analogous to that of the elements of a voltaic pile, and which exist in planes perpendicular to the line which joins the two poles of the magnet.
  5. When a magnet is in the position that it tends to take by the action of the terrestrial globe, these currents move in a sense opposite to the apparent motion of the sun; when one places the magnet in the opposite position so that the poles directed toward the poles of the earth are the same [S to S and N to N, not south-seeking to S, etc.] the same currents are found in the same direction as the apparent motion of the sun.
  6. The known observed effects of the action of two magnets on one another obey the same law.
  7. The same is true of the force that the terrestrial globe exerts on a magnet, if one admits electric currents in planes perpendicular to the direction of the declination needle, moving from east to west, above this direction.
  8. There is nothing more in one pole of a magnet than in the other; the sole difference between them is that one is to the left and the other is to the right of the electric currents which give the magnetic properties to the steel.
  9. Although Volta has proven that the two electricities, positive and negative, of the two ends of the pile attract and repel one another according to the same laws as the two electricities produced by means known before him, he has not by that demonstrated completely the identity of the fluids made manifest by the pile and by friction; this identity was proven, as much as a physical truth can be proven, when he showed that two bodies, one electrified by the contact of [two] metals, and the other by friction, acted upon each other in all circumstances as though both had been electrified by the pile or by the common electric machine [electrostatic generator]. The same kind of proof is applicable here to the identity of attractions and repulsions of electric currents and magnets.

“Here Ampère only hinted at the noumenal background. Like most Continental physicists, he felt that electrical phenomena could be explained only by two fluids and, as he pointed out in the paper, a current therefore had to consist of the positive fluid going in one direction and the negative fluid going in the other through the wire. His experiments had proved to him that this contrary motion of the two electrical fluids led to unique forces of attraction and repulsion in current-carrying wires, and his first paper was intended to describe these forces in qualitative terms. There was one problem: how could this explanation be extended to permanent magnets? The answer appeared deceptively simple: if magnetism were only electricity in motion, then there must be currents of electricity in ordinary bar magnets.

“Once again Ampère’s extraordinary willingness to frame ad hoc hypotheses is evident. Volta had suggested that the contact of two dissimilar metals would give rise to a current if the metals were connected by a fluid conductor. Ampère simply assumed that the contact of the molecules of iron in a bar magnet would give rise to a similar current. A magnet could, therefore, be viewed as a series of voltaic piles in which electrical currents moved concentrically around the axis of the magnet. Almost immediately, Ampère’s friend Augustin Fresnel, the creator of the wave theory of light, pointed out that this hypothesis simply would not do. Iron was not a very good conductor of the electrical fluids and there should, therefore, be some heat generated if Ampère’s views were correct. Magnets are not noticeably hotter than their surroundings and Ampère, when faced with this fact, had to abandon his noumenal explanation.

“It was Fresnel who provided Ampère with a way out. Fresnel wrote in a note to Ampère that since nothing was known about the physics of molecules, why not assume currents of electricity around each molecule. Then, if these molecules could be aligned, the resultant of the molecular currents would be precisely the concentric currents required. Ampere immediately adopted his friend's suggestion, and the electrodynamic molecule was born. It is, however, a peculiar molecule. In some mysterious fashion, a molecule of iron decomposed the luminiferous ether that pervaded both space and matter into the two electrical fluids, its constituent elements. This decomposition took place within the molecule; the two electrical fluids poured out the top, flowed around the molecule, and reentered at the bottom. The net effect was that of a single fluid circling the molecule. These molecules, when aligned by the action of another magnet, formed a permanent magnet. Ampere did not say why molecules should act in this way; for him it was enough that his electrodynamic model provided a noumenal foundation for electrodynamic phenomena” (DSB).

Dibner 62; Norman 43; Sparrow 8: Wheeler Gift 763a.

8vo (194 x 122 mm), pp. 68 with five folding engraved plates, stiched as issued, without wrappers.

Item #4775

Price: $12,500.00

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