Popular Science Monthly/Volume 40/February 1892/Sketch of William Edward Weber
|SKETCH OF WILLIAM EDWARD WEBER.|
WITH the death of Weber, June 23, 1891, passed away, as M. Mascart, of the Central Meteorological Bureau of France, has well said, the last representative of that generation of men of science that cast so much luster on the first half of this century. He was also the last survivor of that group of experimenters in Europe and America whose labors gave the world the electric telegraph; the one among them who first demonstrated that communication by electricity was possible and practicable.
William Edward Weber was born in Wittenberg, Prussia, October 24, 1804. He was the second of three sons of the learned theologian, Michael Weber, Professor of Theology at Wittenberg. The other two sons became doctors, both contributed to science, and both co-operated with the subject of this sketch in some important investigation. Weber studied at the Frankean School and the University of Halle, received his doctor's degree in 1826, became privat-docent at Halle in the next year, and Professor-Extraordinary of Physics there in 1828. In 1831 he was appointed to succeed John Tobias Mayer as Professor of Physics in the University of Göttingen. Ho remained there till 1837, when a political event caused his retirement. On the death of King William IV of England and Hanover, the kingdom of Hanover was separated from England by the operation of the Salic law, and fell to Ernest Augustus, Duke of Cumberland, uncle of King William. Ernest was a believer in the supreme right of kings, and set aside the Constitution which William had granted in 1833. At the same time he called on the public officers of the country, including the professors in the university, to take an oath of allegiance to him and of obedience to his new rule. Weber with six of his fellow-professors—Jacob and William Grimm, Dahlmann, Albrecht, Gervinus, and Ewald—protested against the arbitrary act, and refused to conform to it. "The entire effect of our work," they said, "depends not more surely on the scientific value of our teaching than on our personal freedom from reproach. So soon as we appear before the students as men who trifle with their oaths, our efficiency is at an end. And what would the oath of our fidelity and homage be worth to his Majesty the King, if it came from men who had just frivolously set aside another sworn obligation?" For this refusal the seven professors—"the Göttingen seven" they are called—were removed from their chairs, and three of them (Gervinus, Dahlmann, and Jacob Grimm) were expelled from the country. After this event Weber lived in retirement as a private teacher in Göttingen till 1843, when he was called to be Professor of Physics in the University of Leipsic. According to a German biographer, he never felt quite at home in Leipsic, and gladly accepted an invitation in 1849 to his old place in the Georgia Augusta at Göttingen, where he spent the rest of his life, "with rare fullness of enjoyment pursuing his learned work, never anxious about the show of success, but finding complete satisfaction in the peculiar joys of scientific achievement, furnishing thus a shining example in opposition to the restlessness of our age."
With his eldest brother, Ernst Heinrich, who, a physician, with particular devotion to anatomy and physiology, had become interested in the solution of certain difficult questions in physics, Weber engaged in the investigation of some of the phenomena of wave-motion. The result was the publication, in 1825, when Weber was twenty-one years old, of the book Die Wellenlehre auf Experimente gegrundet (The Doctrine of Waves, based on Experiments), a volume of five hundred and seventy-four pages, with eighteen copper plates, mostly engraved by the authors. One of the striking results of the investigations was the discovery that, when a regular series of waves follow each other along the surface of water, the particles at the surface describe vertical circles, the plane of which is parallel to the direction of propagation of the waves, and those lower down ellipses, of which the vertical axis becomes smaller and smaller with increasing depth. The work was, according to the declaration of the authors, the result of such constant and intimate communication between them with regard to all the parts that it was impossible to assign to either of them the separate authorship of any distinct portions.
A few years afterward, at Göttingen, Weber was engaged in another investigation with his brother Eduard Friedrich, who was also a doctor interested in physical studies, of the mechanism of walking, the results of which were published in the book Mechanik der menschlichen Gehwerkzeuge. The salient feature of this work, in which many novel facts were brought out, was the enunciation of the fact that the pressure of the air is a factor in holding the bones in place in the joints.
For several years Weber was occupied mainly with questions of acoustics, on which, as well as upon electricity, heat, and light, he published many important papers.
His title to be regarded as one of the masters in science rests chiefly on his researches in electricity and magnetism. His position as professor at Göttingen brought him into close association with Gauss, who was as devoted to mathematics as Weber was to physics. The two assisted and complemented one another: Weber needed calculations to bring out the bearings of his experimental results, and Gauss was ready to take up any serious problem that needed solution.
Gauss, according to M. Mascart, besides his work in analysis and celestial mechanics, had given his attention to the mathematical theory of electricity and magnetism, in which he found many analogies with that of universal attraction. He had published a memoir describing an experimental method superior to that of Coulomb for verifying the law of magnetic actions, and a general theory of the magnetism of the globe and the relations between the results obtained at different stations. He established a magnetic observatory, where the methods of calculation he had devised were applied; and with Weber's collaboration an extensive association was formed, including the directors of the principal observatories, chiefly in Germany, for making a systematic study, under a common plan, of the continual variations of terrestrial magnetism. The results of this great enterprise were published by Weber from year to year, and collected in a magnetic atlas of the globe. In memory of this initiative, the Meridian of Göttingen is still preserved as the point of departure in a large number of general studies on the distribution of terrestrial magnetism. This common labor led to the installation, by the two co-workers, in 1834, of the first electric telegraph, by which an important date is marked in the history of telegraphy.
The idea of telegraphing by means of electricity was not entirely novel then. Samuel Thomas von Sömmering, of Munich, had experimented upon it with some success in 1809. Ampère, in 1820, and Fechner, in 1829, had proposed the utilization of the magnetic needle for making signals. But none of these efforts had advanced beyond the experimental stage, and they were only of historical value. They illustrate the general principle that a great discovery hardly ever springs from the thought of a single man. But the fact that there were preceding tentatives does not diminish the fame of the man who gathers up and combines the previous results and completes what they had left unfinished. Weber was the first who established a permanent workable telegraph line, and thereby demonstrated the practical value of the electric telegraph. Weber's house in the city was connected with the astronomical and magnetic observatories by a line between three and four kilometres (over two miles) in length. The signals were made by the deviations of the needle of a galvanometer to the right and left and were interpreted according to a conventional alphabet. The use of interrupted or reversed currents did not permit the transmission of more than one or two words a minute, but the speed was increased to seven or eight words by the use of induced currents.
The following first notice of this telegraphic connection was published in one of the numbers of the Göttingischen gelehrten Anzeigen (or Göttingen Scientific Notes) for 1834: "We can not omit to mention an important and, in its way, unique feature in close connection with the arrangements we have described [of the Physical Observatory], which we owe to our Prof. Weber. He last year stretched a double connecting wire from the cabinet of physics over the houses of the city to the observatory; in this a grand galvanic chain is established, in which the current is carried through about nine thousand feet of wire. The wire of the chain is chiefly copper wire, known in the trade as No. 3. The certainty and exactness with which one can control by means of the commutator the direction of the current and the movement of the needle depending upon it were demonstrated last year by successful application to telegraphic signalizing of whole words and short phrases. There is no doubt that it will be possible to establish immediate telegraphic communication between two stations at considerable distances from one another."
Weber's general magnetic and electrical researches, by which his place in the history of science is most conspicuously marked, are described in the Resultate aus den Beobachtungen des magnetischen Vereins (Results from the Observations of the Magnetic Union), published by Gauss and Weber from 1837 to 1843, and in Weber's Elektrodynamische Maasbestimmungen (Electrodynamic Measurements), published from 1846 to 1874. Of these, M. Mascart says that "the thought of measures in mechanical unities was naturally applicable to the reactions which take place between conductors traversed by electric currents and between currents, the laws of which, had been established by Ampère for the permanent effects, and by Faraday for the transient effects produced by currents of induction. Weber found in them a new road and a personal glory. The series of memoirs in the Elektrodynamische Maasbestimmungen constitute an imperishable scientific monument, in which the extent of the descriptions may sometimes appear long to the reader eager to get on, but the attentive study of which is ever fruitful. It is impossible to give an adequate estimate of this work in a short analysis; we shall only point out a few of its salient traits. The invention of electrodynamometry, which depends on the reciprocal action of currents, permitted Weber to subject Ampère's law to a vigorous testing by a method that differed from that of Gauss only by the substitution of coils for magnets. The close study of the deviations produced in galvanometric apparatus by permanent or temporary currents furnished him with a means of devising precise methods of observation, of measuring quantities of electricity corresponding to the discharge by the impulse impressed by them on the magnetic needle, and of estimating the approximate duration of the discharges by a combination of the galvanometer and the electrodynamometer.
In the course of his experimental researches, Weber made known an important formula which includes in a single expression Coulomb's laws of electrostatics. Ampère's laws on the reciprocal action of currents, and the phenomena of induction described by Faraday. Gauss seems not to have been a stranger to the selection of this formula, and the theoretical conceptions which are its basis may give occasion to discussion; but Weber has the merit of having shown all its consequences by establishing for the first time a close connection between phenomena that appear independent. Weber's labors are particularly distinguished by the introduction of the absolute measures which have contributed for several years to the rapid progress of electricity as a subject of pure science and in its industrial applications. To him, in fact, we owe the suppression of a vague terminology in which currents were estimated by the kind of piles and number of couples, the length and size of circuits, or the deviation produced in a dynamometer of which only the number of turns of wire was indicated. The inestimable services that have been derived from the employment of absolute measures justify the attribution of the name of weber to the unity of the current as defined by its electromagnetic action, for which the mechanical unities of Gauss—the millimetre, the milligramme, and the second of mean time—are adopted.
Weber's biographer in Nature gives Sir William Thomson the credit of having been one of the first men of science to recognize the fundamental cliaracter and far-reaching importance of "Weber's work; and, owing mainly to his clear-sighted advocacy of the absolute system of measurement, this system was from the first adopted as the basis for the operations of the British Association Committee on Electrical Standards, appointed originally in 1862. "This system has now become so familiar to electricians, and is taken so much as a matter of course, that it requires some mental effort to recall the state of science when it did not exist, and to appreciate the intellectual greatness of the man to whom it is due. If we consider method and point of view, rather than acquired results, it is not too much to say that the idea of absolute measurements, underlying as it does the conception of the conservation of energy, constitutes the most characteristic difference between modern physics and the physics of the early part of our century. And to no one man is so large a share in this great step due as to Wilhelm Eduard Weber."
Weber, in conjunction with Kohlrausch, determined the relations between electrical and magnetic measurements expressed in the same unities, concerning which there seems to have been some confusion. He determined the chemical actions by electrolysis which correspond with the passage of a unity of current in a second, and by this furnished a practical means of reconstituting that unity in experiments. He pointed out and put in practice some of the most precise methods for determining the numerical value, as related to the fundamental unities, of the electrical resistance of a conductor. His name is also associated with numerous labors for fixing the value of the practical unity of resistance, or the ohm, in terms of the mercurial column.
So retired was Weber's life in his later days that, though his fame had not diminished, the world had almost forgotten that he was still in it; and it is said that when, at the meeting of the German naturalists in Berlin a few years ago, the name of Weber was read in the list of those who had taken part in the first meeting held there in 1828, surprise was expressed at recognizing in their octogenarian friend one who had sat there with Berzelius and Ohm and Heim.
Weber was a corresponding member of the Institute of France, and had been a foreign member of the Royal Society since 1850.