FOOTNOTES:

FOOTNOTES:[19]Wilcke, a Swedish investigator of electric phenomena, constructed in 1762 two machines involving the principle of the electrophorus.—(Brother Potamian.)[20]Brother Potamian has called my attention to the fact that Volta's work on the origin of electricity from two different metals when, though connected, they were yet separated by some moist medium, was curiously anticipated by an observation described by Sulzer, in a book called Nouvelle Théorie des Plaisirs, 1767. In this he states that, if a silver and a lead coin, placed one above and the other under the tongue, be brought in contact a sour taste develops, which he considers to be due to vibrations set up by the contact of the two metals. He seems also to have had a dash of light before the eyes, so that all the elements necessary for the discovery of the voltaic pile were in his hands, and indeed he was making what has since become one of the classical experiments, by which certain physiological effects of the electric current are demonstrated.

[19]Wilcke, a Swedish investigator of electric phenomena, constructed in 1762 two machines involving the principle of the electrophorus.—(Brother Potamian.)

[20]Brother Potamian has called my attention to the fact that Volta's work on the origin of electricity from two different metals when, though connected, they were yet separated by some moist medium, was curiously anticipated by an observation described by Sulzer, in a book called Nouvelle Théorie des Plaisirs, 1767. In this he states that, if a silver and a lead coin, placed one above and the other under the tongue, be brought in contact a sour taste develops, which he considers to be due to vibrations set up by the contact of the two metals. He seems also to have had a dash of light before the eyes, so that all the elements necessary for the discovery of the voltaic pile were in his hands, and indeed he was making what has since become one of the classical experiments, by which certain physiological effects of the electric current are demonstrated.

Great discoverers in science must usually be satisfied with having their names attached to some one phase of scientific development, be it an instrument, a law, a unit of measurement, a process of investigation or some phenomenon which they first observed. The originality of Coulomb's genius will be better appreciated, since besides having a unit of electricity named after him, there is also a law in electro-magnetics and a torsion-balance that will always be associated with his name. Few men have been more ingenious in their ability to put complex ideas into practical shape and give them simple mechanical expression by instrumental methods. While his name is to be forever associated with the science of electrostatics, he was profoundly interested in other departments of physics, and for him to be interested always meant that he would illuminate previous knowledge by practical hints and suggestions and carry the conclusions of his predecessors a little farther into science than they had ever gone before. His was typically an experimental genius, and he must be considered one of the men of whom not more than half a dozen are born in a century, who are, in Kipling's strong term, "masterless"; who do not need to be taught, but who find for themselves a path into the domain of the unknown.

Coulomb investigated the fundamental law in electricity and magnetism, that attractions and repulsions are inversely as the square of the distances, and showed that it held accurately for point-charges and point-poles. He demonstrated that these interesting phenomena were not chance manifestations of irregular forces, but that they represented a definite mode of action of force, thus setting this department of knowledge on a scientific basis. While in practical significance Ohm's Law, discovered nearly a half century later, is of much more import, Coulomb's discoveries are fundamental in character and, coming in the very beginnings of modern electrical science, did much to guide the infant science in the ways it should follow. The establishing of this law contributed very largely to the rapid development of the twin sciences of electricity and magnetism. It is experimental observation that means most for a rising science; and, in fact, that Coulomb should have been the pioneer in it stamps him as possessed not only of great originality, but also of the power of independent thinking, which is perhaps the most precious quality for the man of science.

The French investigator succeeded in demonstrating his law by two distinct methods which are still used for illustration purposes in our physical laboratories. In the first, he employed the torsion-balance devised by Michell, and re-invented by himself, an instrument of exact measurement which, in his hands, yielded as invaluable results as it did in those of Faraday half a century later. The instrument depends on the principle first established by Coulomb himself, that when a wire is twisted, the angle of torsion is directly proportional to the force of torsion. In the application of this principle, a fine wire is suspended in a glass case, on the sides of which there is a graduated scale to measure the degree of repulsion between two like poles of a magnet or between similarly electrified bodies.

In his second research on the law of the inverse square, Coulomb used what is known as the method of oscillations. A magnetic needle swinging under the influence of the earth's magnetism is known to act like a pendulum, and as such obeys the laws of pendular motion. In applying this method, Coulomb caused the magnetic needle to oscillate, first, under the influence of the earth's magnetism alone and then under the combined influence of the earth and the magnet placed at varying distances from the needle. The most interesting feature of this work is the manner in which Coulomb succeeded in eliminating the important factor of the earth's magnetism from the problem. It is so simple and ingenious that it commands the admiration of investigators, who employ it in their laboratory work even to the present day.

It is clear, then, that the International Committee which selected the term coulomb for the electromagnetic unit of electrical quantity gave honor where it was eminently due. Coulomb stands out as a man of precision and accuracy, whose methods of exact measurement revolutionized the rising science, and whose researches and discoveries in physics and mechanics furnish ample justification for giving him a place among the makers of electricity. He was one of the gifted men whose original works ushered in so gloriously the nineteenth century, and who laid the deep and firm foundations on which the last three generations have built up the magnificent temple ofelectrical science.

Charles Augustin de Coulomb was born at Angoulême, June 14th, 1736. His ancestors for several generations had been magistrates, and were looked upon as representatives of the country nobility. He made his university studies in Paris, and while still young, entered the army. From the very beginning, however, his genius for mathematics was recognized, and he was employed in the capacity of military engineer. To Americans, it will be interesting to know that his first engineering project was undertaken at Martinique, where he constructed Fort Bourbon. His sterling character and remarkable ability secured him rapid advancement in the service. In spite of the fact that the climate did not agree with him, he remained for three years on the island, because he would not employ the political influence that might have secured his recall, since he thought it his duty to serve his country in an important colonial post. Nearly all his comrades perished by fever. It is the irony of fate that after his return to France a change in the ministry deprived him of the just recompense of his devotion to country, and he did not receive the special extraordinary promotion which he had earned in this special detail.

During a short stay that he made at Paris after his return, he sought the society of men of science as far as possible, and succeeded in getting in touch with all that was most promising in scientific progress at the time. He was already known rather favorably by many of the scientific men of the capital because of the paper on The Statics of Vaults, a monograph on static problems in architecture, which he presented to the Academy of Sciences in 1779. His next military assignment was toRochefort. Here he composed his monograph on "The Theory of Simple Machines," which carried off the double prize that had been offered by the Academy of Sciences for the solution of problems connected with this important question. This attracted the attention not only of the scientific world, but also of his military superiors. As a result, he was sent successively to Cherburg and to the Isle of Aix, to direct engineering works, and accomplished the tasks involved with success.

Two years later, when he was about forty-five years of age, he was elected member of the Academy of Sciences by a unanimous vote. He was a man of great personal magnetism, and all those who came in contact with him learned to like him for his straightforward character and for the absolute righteousness of his life. Few men have made firmer friends than Coulomb, as few have ever shown more unselfish devotion to duty and to conscience than he, though under circumstances that were neither spectacular nor theatrical. It was harder to face the deadly climate of Martinique than it would have been to take one's place at the head of a forlorn hope in an outburst of enthusiastic courage; and Coulomb was to have other trials of quite as deterrent a nature, and was to meet them with the same imperturbed sense of duty.

Graft is sometimes supposed to be temptation peculiar only to our own times, but the opportunities for it have always been present in such work as Coulomb had to oversee, and the army engineer of all ages has had to stand or fall before it. It was proposed, about this time, to build a system of government canals in Brittany. Such a canal-system would, as is easy to understand, cost an enormous sum of money and give magnificent opportunities for speculation of various kinds. No small objection had been made to the project, on the score that it would not confer all the benefits on the region that were claimed for it, and Coulomb was commissioned by the Minister of Marine to determine the question of the advisability of constructing the canals, and of the probable effect which they would have on the commerce of the country.

After careful investigation, he came to the conclusion that the advantages which were expected to accrue from the project would not compensate for the enormous expense that would be entailed. This decision aroused the angry protest of a strong political faction, who expected to reap wealth and personal advantages of many kinds from the scheme, and who protested bitterly against Coulomb's report. He was able to support his conclusions in the matter, however, with such unanswerable mathematical and engineering arguments, that his opinion prevailed and the project was given up.

As a consequence, instead of the opportunity to serve a political party with every avenue to preferment and, above all, to wealth open for him, he found himself, for the time being, deprived even of the opportunity to devote himself further to his favorite occupations in military engineering. The excuse given for this interruption in his career, for there has always been an excuse for such action, was that proper representations for permission to make the report had not been made to the Minister of Marine; and instead of commendation, Coulomb received what was practically a reprimand.

Wounded by this injustice, which was manifestly due to the fact that his honest report had displeased those who expected to reap personal benefit from the canal project, and disgusted with a service in which such things were possible, Coulomb sent in his resignation. The Minister of Marine realized that the acceptance of the proffered resignation would surely expose the ministry at least to suspicion as to the reasons why Coulomb's report was not accepted with good grace. Permission to retire from the service was refused, as this would insure his silence. He was ordered back to Brittany to continue his work there, possibly with the idea that this unfavorable experience would be sufficient of itself to make him understand what was expected of him and render him a little more complacent to the wishes of those in authority. If any such ideas were entertained, they were destined to grievous disappointment. Coulomb was not of those who, seeing duty plainly, refuse to follow it because some personal advantage or disadvantage intervenes. Selfish reasons did not appeal to his character nor obscure the issues.

He went back to Brittany, ready to express his firm opinion in the matter and with integrity of soul untouched. The consequence was that the provincial authorities, recognizing their true interests, acknowledged the error they had come near falling into, and now wished to reward the engineer handsomely for his unswerving devotion to duty. Coulomb as promptly refused a reward for doing his duty as he had ignored even the appearance of a bribe to avoid it. Only after considerable pressure was he prevailed upon to accept the best timepiece they could procure, on which the arms of the province were engraved. It had what was quite rare in those days, a second's hand, and he constantly made use of this in all his experimental work thereafter. A French biographer says that, never was a souvenir better chosen nor more suitably employed. Coulomb's merits were recognized by the government authorities not long after, and he was made superintendent of the fountains of France. A few years later, he was promoted to the position of Curator of Plans and Relief Maps of the Military Staff of France, and was chosen as one of the commission of the French Academy of Sciences who went to England in order to study hospital conditions there. At this time, he was at the acme of his career. His grade was that of Lieutenant Colonel of Engineers, a position much higher in the foreign armies at that time than would be the post with the corresponding title in our army. He had been made a Chevalier of St. Louis, and it looked as though a brilliant future were opening out before him. Each year, for a decade, had seen the publication of one or more memoirs on important subjects, nearly every one of which contained some original material of the highest value, destined not only to add to Coulomb's reputation, but to furnish basic information for the further development of science.

In 1789, however, the Revolution broke out, and there was an end to all Coulomb's opportunities for work. He was utterly out of sympathy with the movement, the worst consequences of which he foresaw from the beginning, and he at once handed in his resignation of the various positions that he occupied under the government. He went into almost absolute retirement, devoting himself to the education of his children. During this time, however, he did not cease to cultivate science, inasmuch as he gave the finishing touch to various papers which he had previously outlined. Unfortunately, however, his departure from Paris made it impossible for him to continue his investigations in electricity for want of apparatus, and so there is a ten years' interruption in his life of scientific activity and of original work. Besides, it cannot be surprising that he should not have had the heart to go on with his work under the awful social conditions that prevailed. Many of his friends lost their lives during the stormy period of the Revolution; most of the others were banished or were in hiding. His beloved country had gone into an unfortunate eclipse, as he could not help but consider it; most of the nations of the earth were indeed in league against her, and the end was not yet in sight. It would be too much to expect of human nature that it should devote itself to abstruse problems in science at moments of such disturbance as this, and so some of the possibilities of Coulomb's original genius were lost to science during that calamitous period.

Like many of the great discoveries of science, Coulomb's most important work was done in the course of other investigations, and came by what might be called a happy accident. He had been investigating the qualities of wire of various kinds, especially with regard to their elasticity, so as to be able to determine the limits of their use in various engineering projects. When he discovered that the elasticity of torsion of a wire was a constant property, he proceeded to utilize it in the calculation of such delicate phenomena as those of electric and magnetic forces. The first instrument for this purpose that he constructed consisted simply of a long magnetized needle suspended horizontally by a fine wire. Supposing this needle to be at rest, if one moves it away from the magnetic meridian by a certain numberof degrees, the twisted wire will have a definite tendency to untwist and to bring back the needle to its original position by a series of oscillations whose frequency can be readily observed.

For such observations, it is possible to obtain the value of the force acting on the needle and causing it to move to and fro at a given rate. This was the underlying idea which received very simple expression in the ingenious instrument which Coulomb devised and called a torsion-balance. With it, he set about determining the law which governs the mutual action of magnets and of electrified bodies with regard to distance, and found it to be the same as that which Newton found to hold for bodies distributed throughout the universe, that is, that attraction and repulsion vary inversely as the square of the distance. He also proved, with the aid of his torsion-balance, that the forces of attraction and repulsion vary as the product of the strength of the poles in one case and as the product of the electric charges in the other. These were the important discoveries of Coulomb's life; they served to earn for him the right to have his name given to the unit of electrical quantity, thecoulomb.

Coulomb did not stop here, however, but proceeded to apply his laws to various other phenomena. He proved that electricity distributes itself entirely over the surface of a body without penetrating the mass of the conductor, and he showed by calculation that this result was a necessary consequence of the law of repulsion.

A list of the papers which he published on electricity and magnetism, the titles of which, with French accuracy of expression, furnish an excellent idea of their contents, shows the thoroughly progressive and scientificspirit of the man, and how well he proceeded from the known to the less known, always widening the bounds of knowledge. Suffice it to say here that the observations of Coulomb were not only original, but that they concerned some of the most difficult questions in electricity, and that he was clearing the ground for others in such a way as to make future work and quantitative measurements in electricity reliable and comparatively easy. It is because of this pioneer work that Coulomb deserves so much praise. It was not long before Coulomb's observations were confirmed by others, and then the beginnings of the modern development of electricity became manifest, owing not a little to the researches and inventions, the genius and ingenuity of this French military engineer.

Some phases of electrical development attributed to others really belong to Coulomb. A typical example of this detraction from his merit is the attribution to Biot of the solution of the problem of the complete discharge of an electrified sphere by means of two hollow hemispheres. This experiment is fully described by Coulomb, and he even emphasizes the fact that the external discharging bodies need not necessarily be of the same shape as the charged sphere. Some of what Coulomb accepted as principles in electricity have proved in the course of time, not to be the realities that he thought them; but the progress that has led to such contradictions of his opinions has been mainly rendered possible by his own discoveries. The fable of the eagle stricken by the arrow containing some of its own feathers, is so old that one might think that, when the progress of a science due to a scientist brings men beyond the position he occupied, they would not blame himfor backwardness. This is, however, one of the curious critical methods in the history of science that has most frequently to be deprecated by the historian who is tracing origins and developments.

Coulomb's papers, with the exception of his memoir on "Problems in Statics Applied to Architecture," his "Researches on the Methods of executing Works under Water without the Necessity of Pumping," his "Theory of Simple Machines," and his researches "On Windmills," which form separate monographs, were all published together in a single volume by the French Physical Society in 1884.[21]

This volume contains, besides his investigations on the best way of making magnetic needles, his theoretic and experimental investigations on the force of torsion and on the elasticity of metallic threads, which were undertaken in order to enable him to make his electric torsion-balance something more than mere guess-work. All the other papers are concerned directly with electricity or magnetism, and show how actively, nearly a hundred and twenty-five years ago, a great mind was engaged with problems in electricity which we are apt to consider as belonging more properly to our own time. The list of papers published in these memoirs, arranged in chronological order, gives a good idea of the development of electrical science in Coulomb's own mind. There is a logical as well as a chronological order to be observed in them.

In 1785, when he was just approaching his fiftieth year, there were three subjects with regard to whichCoulomb's experimental observations enabled him to set down some definite principles. The first of these was the construction and use of an electric balance, founded on the property which wires have of exhibiting a torque proportional to the angle of torsion. The second was the determination of the laws, according to which the magnetic and electric "fluids," as Coulomb and investigators in electricity called them at that time, act both as regards repulsion and attraction. The third was the determination of the quantity of electricity which an insulated body loses in a given time from contact with air more or less moist.

In 1786, he published a paper in which he demonstrated what he considered the principal properties of the electric fluid. These are, that this fluid does not spread itself on a substance by any chemical affinity or any elective attraction, but that it distributes itself over various bodies that are placed in contact, entirely in accordance with their shape; and also that in electrical conductors, the charge is limited to the surface of the conductor and does not penetrate to any appreciable depth.

In 1787, his only paper was on the manner in which the electrical fluid divides itself between two conducting bodies placed in contact, and on the distribution of this fluid over the different parts of the surface of these bodies. He continued his investigations into this subject in 1788, and also succeeded in determining the density of the electricity at different points on the surface of conducting bodies.

In 1789, he began to work more particularly on magnetism. His first paper on the subject was published that year. Unfortunately, as we have said, the Revolutioninterrupted his scientific investigations at this point, and for the next eleven years we have nothing from his pen. As a nobleman, he was compelled to leave Paris, and this not only put him out of touch with scientific work generally, but deprived him of the opportunities of using such apparatus as was necessary to carry on his experiments. That he acted prudently in leaving Paris, the careers of other scientists amply prove. Lavoisier continued to carry on his chemical investigations during the stormy times of the Revolution, but his stay in the capital eventually cost him his life. Abbé Haüy, the father of crystallography,[22]who, because of his contributions to the science of pyro-electricity, is of special interest to us, continued to work at his crystals throughout even the Reign of Terror. When thrown into prison, he asked and obtained permission to have his crystals with him. His friends saved him from Lavoisier's fate, but not without an effort, as his life was seriously endangered.

It is easy to understand, however, that a member of the nobility like Coulomb, whose life had been spent in military affairs, should not be able to devote himself seriously to scientific matters while his country was in such a turmoil.

In 1801, he resumed his investigations once more, but now they are concerned more particularly with magnetism. The first was a theoretical and practical determination of the forces which hold different magnetic needles, magnetized to saturation, in the magnetic meridian. This was followed, in the same year, by a paper which, like its predecessor, was published among the memoirs of the Institute of France, which had replacedthe Royal Academy of Sciences, to which body many of Coulomb's papers of the former time had been presented, and in whose publications they originally appeared. This second paper detailed his experiments on the determination of the force of cohesion of fluids and the law of resistance in them, when the movements were very slow.

When the French Institute was organized under Napoleon in 1801, Coulomb was named among its first members. It is believed that he was even chosen to occupy a place in the first government of the state, but a man more interested in politics obtained the place, a fortunate circumstance for science. Coulomb was named, however, one of the inspectors of public instruction, then the highest place in the education department, and he did much to restore to France the educational system that had been destroyed during the Revolution. In this rather trying work he was noted for the kindliness yet firmness of his character, while his absolute fairness and sense of justice were recognized on all sides.

Unfortunately Coulomb was not long spared to continue his work. He took up his experimental and mathematical investigations, on his return to the capital, with great enthusiasm, but his health had been undermined and his work had been rudely interrupted. After 1801, no further paper by him appears to have been published until 1806. This gave the result of different methods employed in order to produce in blades and bars of steel the greatest degree of magnetism. For some time preceding this, in spite of increasing ill-health, he had continued his experiments on the influence of temperature on the magnetism of steel.His work on this subject was not destined to be completed, for not long after passing his seventieth year, in June of this year, his health gave way completely, and he died August 23d, 1806. His final observations were gathered by Biot, carefully preserved, and assigned a place in the volume of Coulomb's Memoirs, issued by the French Physical Society.

Personally, Coulomb was noted for great seriousness of character, though with this was mingled a gentleness of disposition that made for him some cordial friendships among his scientific contemporaries. He had but few friends, but those who were admitted to his intimacy made up by the depth of their affection for the smallness of their number. Even those who had occasion to meet him but once or twice, carried away from their meeting an affectionate remembrance of his kindliness and courtesy and readiness to help wherever he could be of service. He was extremely happy in his family relations, and this proved to be a great source of consolation to him during the years when the progress of the French Revolution took him away from science and made him almost despair of his country.

It is not surprising that Biot, the great French physicist, in writing of Coulomb in his Mélanges Scientifiques et Littéraires, Vol. III. (Paris, 1858), should have held Coulomb up as a model of the simple, earnest, helpful life and as a man of the most exemplary character. He says: "Coulomb lived among the men of his time in patience and charity. He was distinguished among them mainly by his separation from their passions and their errors, and he always maintained himself calm, firm and dignifiedin se totus teres atque rotundus, as Horace says, a complete, perfect and well-rounded character."Few men have deserved so noble a eulogy as this, written nearly fifty years after his death, by one who had known Coulomb himself and his contemporaries well; it has none of the exaggeration of a funeral panegyric, and is evidently founded on details of knowledge with regard to the great electrician which had become a tradition among French scientists, and which Biot has forever crystallized into the history of science by his emphatic expression.

One could scarcely wish for a better epitaph than Biot's summing up of Coulomb's personal character: "All those who knew Coulomb know how the gravity of his character was tempered by the sweetness of his disposition, and those who had the happiness to meet him at their entrance into a scientific career have kept the most tender remembrance of his gentle good-heartedness."

FOOTNOTES:[21]Collection de Memoires relatifs à La Physique Publiés Par la Société Française de Physique. Tome I., Mémoires de Coulomb. Paris. Gauthier-Villars, Imprimeur-Libraire Du Bureau des Longitudes, de L'École Polytechnique, Quai des Augustins, 55, 1884.[22]Catholic Churchmen in Science, the Dolphin Press, Philadelphia, 1906.

[21]Collection de Memoires relatifs à La Physique Publiés Par la Société Française de Physique. Tome I., Mémoires de Coulomb. Paris. Gauthier-Villars, Imprimeur-Libraire Du Bureau des Longitudes, de L'École Polytechnique, Quai des Augustins, 55, 1884.

[22]Catholic Churchmen in Science, the Dolphin Press, Philadelphia, 1906.

Hans Christian Oersted

Whatever may be thought of the value of controversy in other departments of knowledge, it has certainly proved useful in the progress of experimental science. Witness the animated and prolonged discussion which took place between Volta and Galvani, and which led to enduring results for the welfare of mankind. Wishing to prove the correctness of his theory of electrification by contact against Galvani's animal electricity, Volta devoted himself unremittingly to experimentation until, in the century year 1800, his brilliant work culminated in the invention of the "pile" or electric battery which bears his name.

A suspicion had been growing for many years in the minds of physicists, that there must be some degree of relationship, probably an intimate one, between magnetism and electricity, between magnetic and electric forces. In the year 1785, van Swinden, a celebrated Dutch physicist, published a work on electricity in which he described and commented upon a number of analogies which he had observed between the two orders of phenomena; but, voluminous as was the work, it threw no light on the nature of the suspected relationship.

It was well known, in the case of houses and ships struck by lightning, that knives, forks and other articles made of steel were often found to be permanently magnetized.Following up this pregnant observation, experimenters often sought to impart magnetic properties to steel needles by Leyden-jar discharges, but with indifferent success. Sometimes there would be a trace of magnetism left and sometimes none. In no case was it possible to say beforehand which end of the knitting-needle would have north polarity and which south.

Though we are better equipped to-day for research work than were our predecessors in the electrical field fifty years ago, we are still unable to predict the polarity that will result in a bar of iron from a given condenser discharge. The uncertainty arises from the fact disclosed by Joseph Henry in 1842 and well known to-day that, under ordinary circumstances, all such discharges consist of a rush of electricity to and fro, that is, they give rise to an oscillatory current of exceedingly short duration. Were it otherwise, that is, were the discharge unidirectional, the needle would always be magnetized to a degree of intensity proportional to the energy released; and it would be possible in every case to foretell with certainty the resulting polarity which the needle would acquire.

With the advent of the voltaic battery, a generator which supplies a steady flow of current in one direction, the interesting problem of relationship between electric and magnetic forces was again attacked; and this time with considerable success.

Probably the earliest investigator afield was Romagnosi, an Italian physician residing in Trent (Tyrol), who, in the year 1802, published in the "Gazetta" of his town an account of an experiment which he had made, and which showed that he was working on promising lines. What he did was this: having connectedone end of a silver chain to a voltaic pile, and having carried the chain through a glass tube for the purpose of insulation, he presented the free end, terminating in a knob, to a compass-needle, also insulated. At first, the needle was attracted; and, after contact, repelled. Whatever Romagnosi thought of his experiment and its theoretical bearing, the attraction and subsequent repulsion of the compass-needle which he said he observed were electrostatic and not electromagnetic effects. The Italian physician was indeed on the verge of a great discovery; but he halted in his course and lost his opportunity.

Mojon, Professor of chemistry in Genoa, was a little more fortunate, though he, too, failed to improve his opportunities. In 1804, he sought to magnetize steel needles by placing them for a period of twenty days in circuit with a battery of one hundred elements of the crown-of-cups type, and had the satisfaction of finding them permanently magnetized when withdrawn from the circuit. Unlike the electrostatic effect of his fellow-countryman Romagnosi, this was unquestionably an electromagnetic effect, the first link in the long chain connecting electricity with magnetism.

That this result attracted wide attention at the time, as it well deserved, is evident from the notice given by Izarn in his "Manuel du Galvanisme," and by Aldini in his "Essai Théorique et expérimental sur le Galvanisme," both of which were published in Paris in the same year, 1804.

Though the manuals of Izarn and Aldini served to give a fresh impetus to the quest of the relationship between electricity and magnetism, it was not, however, until the year 1820 that the cardinal discovery was madeby one philosopher and the intimate relationship revealed by another. Then all Europe rang with the names of Oersted, the fortunate discoverer of the "magnetic effect" of the electric current, and Ampère, whose masterly analysis disclosed the nature of the long-sought-for connection. In the delight of the hour, men called Oersted the Columbus, and Ampère the Newton, of electricity.

Though a philosopher of a high order and lecturer of interest and brilliancy, Oersted was, nevertheless, a poor experimentalist. He was fine in the abstract, awkward in the concrete. Often did he call for the assistance of a student to perform an experiment for the class under his direction. Hansteen, who is celebrated for his very fine work in terrestrial magnetism, often had this privilege, for he was clear of mind and deft of hand. Writing to Faraday, he said: "Oersted was a man of genious, but very unsuccessful as a demonstrator, for he could not manipulate instruments."

In seeking for some evidence of a physical interaction between electricity and magnetism, Oersted on one occasion, placed a wire conveying a current vertically across a compass-needle; and, on obtaining no result, seemed greatly disappointed. He evidently expected the needle to respond in some way to the energy of the current; and so it would have responded had he placed the wire in any other position than the particular one which he selected. The Danish philosopher now hesitates; and for lack of coolness, patience and resourcefulness, runs the risk of losing the crowning glory of his life. He is disappointed at his failure; and for the nonce, contents himself with brooding over it.

Fig. 22The Magnetic Effect of an Electric Current. Oersted, 1820

On another occasion, having a stronger battery at his disposal, he determined to try the experiment again, in the hope that the greater energy at his command would provoke the magnet to respond. This time, he stretched the wire over and parallel to the compass needle, when, to his intense delight, the magnet turned aside as soon as the circuit was closed. The result was pronounced and instantaneous. The Professor, an enthusiast by nature, waxed warm over his good fortune, and well might he do so, as the discovery which he had just made was destined to revolutionize existing modes of transmitting intelligence to distant parts and bring remotest countries into direct, and immediate relation with one another.

That Oersted fell into ecstasy over his success was but natural, though it is not stated that he exhibited his enthusiasm by the performance of any unusual feat. When Lavoisier made a discovery, he was wont to take hold of his assistant and go dancing around with him for sheer joy. After making a certain successful experiment in his laboratory, Gay-Lussac gave vent to his feelings by dancing round the room, and clapping his hands the while. It is related that, when Davy saw the first globules of potassium burst through the crust of potash and take fire, his delight knew no bounds. He also took to dancing, and some time had to elapse before he was sufficiently composed to continue his work. Eventhe cool and self-possessed Faraday occasionally waxed warm on seeing his efforts crowned with success. It is said that, when he got a wire conveying a current to revolve round the pole of a magnet, he rubbed his hands vigorously and danced around the table, his face beaming with delight: "There they go, there they go; we have succeeded at last," he said. He then gleefully proposed to cease work for the day and spend the evening at Astley's seeing the feats of well-trained horses!

Having realized that his experiment was one of fundamental importance in physical theory, our philosopher proceeds to repeat it under varying conditions. He places the wire conveying the current in front of the needle, behind it, under it, across it; he reverses the current in each case, and notices the direction in which the needle turns. Though he states results very clearly, he gives no general rule whereby the direction of the deflection may be foretold from that of the current. Amemoria technicato meet all cases that may occur was needed, and was promptly supplied by Ampère, who, with a flash of genius, devised the rule of the little swimmer. Others have been added since, such as the cork-screw rule and the rule involving the outspread right hand; but the swimmer appeals in a manner quite its own to the fancy of the youthful student. It pleases while it instructs; it is ingenious while yet remarkably simple.

It has been said that the Philosopher of Copenhagen was led by mere accident to the experiment which will hand his name down the ages; but inasmuch as he was looking, during thirteen years, for a result analogous to the one which he obtained, it is only right to give him full credit for the success which he achieved. It hasbeen well remarked, that the seeds of great discoveries are constantly floating around us, but take root only in minds well prepared to receive them. Accidents of the Oersted type happen only to men who deserve them, as was the case with Musschenbroek and Galvani in the eighteenth century, and with Roentgen in the nineteenth. The electrification of a flask of water, the twitching of frogs' legs in response to electric sparks, and the blackening of a sensitive screen by a distant, shielded Crookes's tube, led to the electrostatic condenser in the first case, to "galvanism" in the second, and to the photography of the invisible in the third.

Writing of Oersted's discovery, Faraday said that "It burst open the gates of a domain in science, dark till then, and filled it with a flood of light."

The discovery of 1820 was hailed throughout Europe by an extraordinary outburst of enthusiasm. Oersted was complimented and congratulated on all sides. Honors were showered upon him: the Royal Society of London awarded him the Copley medal; the French Academy of Sciences gave him its gold medal for the physico-mathematical sciences; Prussia conferred upon him the Ordre pour le Mérite, and his own country made him a Knight of the Daneborg.

Oersted lost no time in preparing a memoir on the subject of his work, a copy of which was sent to the learned societies and most renowned philosophers of Europe. The memoir, which was written in Latin and dated July 21st, 1820, consisted of four quarto pages with the title "Experiments on the effect of the electric conflict on the magnetic needle."

A perusal of this paper brings home the conviction that Oersted realized fairly well the forces which came into play in his experiment; for in one place, he speaks of the effect as due to a transverse force emanating from the conductor conveying the current, and again as a conflict acting in a revolving manner around the wire. A complete statement of the nature of the mechanical force exerted by a conductor conveying a current on a magnetic needle was given almost immediately by Ampère, a master analyst and accomplished experimentalist.

Fig. 23Magnetic Field Surrounding a Conductor Carrying a Current

It will stand for all time in the history of science, that in less than two months after the publication of Oersted's memoir, Ampère succeeded in showing the mechanical effect in magnitude and direction of an element of current not only on the magnetic needle itself, but also on a similar element of an adjacent conductor conveying a current, thereby founding a new science in the department of physics, the science of electro-dynamics.

Oersted does not appear to have given thought to the practical possibilities of his discovery. While appreciating the utilitarian in science, he evidently preferred the pursuit of knowledge for its own sake. In a discourse which he delivered in 1814 before the University of Copenhagen, he put himself on record when he said that "The real laborer in the scientific field chooses knowledge as his highest aim."

So said Plato ages before, and so said Archimedes, who held that it was undesirable for a philosopher to seek to apply the discoveries of science to any practical end. The screw which he invented, his catapults and burning mirrors, show, however, that when necessary the Syracusan mathematician could come down from the serene heights of investigation to the prosaic arena of application.

Before Oersted spoke of "the real laborer," Thomas Young had affirmed that "Those who possess the genuine spirit of scientific investigation are content to proceed in their researches without inquiring at every step what they gain by their newly discovered lights, and to what practical purposes they are applicable."

Fig. 24Magnetic Whirl Surroundinga Wire Through Which a Current is Passing

Young's most illustrious successor in the Royal Institution, Michael Faraday, devoted himself calmly but unflinchingly to research work, in the conviction that no discovery, however remote in its nature, from the subject of daily observation, could with reason be declared wholly inapplicable to the benefit of mankind. After discovering in 1831 that electric currents could be produced by the relative motion of magnets and coils of wire, a discovery which is the basis of all the electric engineering of our day, Faraday constructed several experimental machines embodying this principle, and then turned away abruptly from the work, saying, "I had rather been desirous of discovering new facts and new relations dependent on magneto-electric induction than of exalting the force of those already obtained, being assured that the latterwould find their full development hereafter."

Our own Joseph Henry, whose sterling merit is universally recognized, beautifully said in this connection: "He who loves truth for its own sake feels that its highest claims are lowered by being continually summoned to the bar of immediate and palpable utility."

Oersted seems to have shared the opinion largely held by the scientific men of his day, that electricity is mainly a magnetic phenomenon. Ampère, for one, did not think so, as is evident from the beautiful theory which he devised to explain the magnetism of a bar by minute electric currents flowing round each individual molecule of the iron. To the French physicist, magnetism was purely an electrical phenomenon.

Fig. 25Ampère's Molecular Currents

Though propounded more than eighty years ago, this theory is still in harmony with all facts and phenomena in the domain of magnetism known to-day. It is important to remember, when thinking of this physical theory, that the Amperian currents in question are confined to the molecule, and that they do not flow from one molecule to another. Critics have urged against the theory that the molecules must be heated by the circulation of these elementary currents, to which objection it has been replied that, as we know nothing of the nature of the molecule, we cannot say that it offers any resistance to the current; and, therefore, we cannot affirm that there is any development of heat due to the circulation of these elementary currents.

It is to Ampère's credit that he was also the first to propose a practical application of Oersted's discovery, an application that was nothing less than the electric telegraph itself. He suggested that the deflection of the magnetic needle could be used for the transmission of signals from one place to another by means of as many needles and circuits as there are letters in the alphabet. If Ampère had only recalled the optical and mechanical telegraphs in use in his day, such as the swinging of lanterns by night and wigwagging of flags and the movements of semaphores by day, he might have reduced his twenty-four circuits to one, using the two elements, viz., motion of the needle to the right and motion to the left, to make up the entire alphabet. Morse substituted the dot and the dash for these deflections, and thus rendered the reception of messages automatic and permanent.

In connection with this proposal to use a magnetic needle for the transmission of intelligence, the reader will no doubt recall the lover's telegraph, so beautifully described by Addison in the "Spectator" for December 6th, 1711; but ingeniously conceived as it was, this magnetic telegraph was purely and simply a creation of the imagination.

This canny conceit has been attributed to Cardinal Bembo, the elegant scholar and private secretary to Pope Leo X.; but it was his friend Porta, the versatile philosopher, who made it widely known by the vivid description which he gave of it in his celebrated work on "Natural Magic," published at Naples in 1558.

This sympathetic telegraph consisted, we are told, of a magnetic needle poised in the center of a dial-plate, with the letters of the alphabet written aroundit. The two fortunate individuals privileged to holdwirelesscorrespondence with each other having agreed as to the day and the hour, proceed to the room in which the wonderful instrument is kept, where, as soon as one of them turns the needle of his transmitter to a letter, the distant needle turns at once in sympathy to the same letter on its dial!

Such is the power of magnetic sympathy, that the instruments will work successfully though hills, forests, lakes or mountains intervene! Porta has it: "To a friend at a distance shut up in prison, we may relate our minds; which, I do not doubt, may be done by means of compasses having the alphabet written around them."

Back to Index Next