him a special interest, such as a point of science to discuss or error to combat, than he was seen to put forth a boldness, a force of intellect, an eloquence which would scarcely have been suspected from his modest exterior and reserved demeanor.

He first traversed a great part of Germany, passed six months at Berlin, and sojourned for some time at Friburg, Jena, and Munich. A new life then animated that country. Poets and philosophers of eminence had there given to the human mind an unexpected impulse. This movement bore especially on the natural sciences, and that assemblage of somewhat vague ideas which was called the philosophy of nature was in process of development. Oersted, with his philosophic and poetic views on the unity and the beauty of nature, was sufficiently disposed to lend attention to the new German doctrines, and he himself avows their influence by saying, in the preface of one of his works, published in 1813: "The philosophy of nature, which has been cultivated within 20 years in Germany, might also assert its claim to some of the views which we are about to offer." Yet he never allowed himself to be turned aside from the severe and positive study of facts and of experiment.

He enjoyed constant conversations with Klaproth, Hermstadt, Paul Erman, Trommsdorff, with Kielmeyer, the master and friend of Cuvier, with the celebrated Werner, at Friburg, and with the profound mineralogist and crystallographer Weiss. He met also Fichte, Schelling, Franz Baader, Schleiermacher, Tieck, and the two Schlegels. But he associated himself more particularly with the ingenious physicist Ritter, already celebrated for his experiments in galvanism, in which he had established, among other things, that a constant development of electricity accompanies the phenomena of life. They executed in common a series of remarkable experiments, and Oersted conceived from that time a high opinion of the scientific capacity of his collaborator, which frequently appears in his writings, and particularly in the following passage of the preface of his Researches on the Identity of Chemical and Electrical Forces, published in 1813: "Ritter may, in this respect, be regarded as a creator. His grand conceptions, and his labors encountered with a zeal which obstacles and sacrifices were incapable of subduing, have shed light on almost all parts of the science." Oersted often expressed the opinion that, with more of sequence in his labors, Ritter would have discovered the electric pile before Volta. Unfortunately Ritter joined with a very ingenious mind great eccentricity, which crippled his pursuits and abridged his days.

After sojourning some time at Munich with Ritter, Oersted published at Ratisbon, in 1803, a small work entitled Materials for a Chemistry of the XIXth Century, in which occur highly interesting views respecting the new horizons opened to chemistry by the discovery of the Voltaic pile. Before parting with Ritter, who remained at Munich, Oersted had rendered him services which could only have been inspired by a warm and sympathizing friendship. He proceeded afterwards to Paris and passed there 15 months in habitual intercourse with Cuvier, Hauy, Vanquelin, Charles, Berthollet, Biot, Guiton-Morveau, Thenard; assiduously following the courses of the distinguished professors and sometimes making communications, on his own experiments, to the Philomathic Society. During his stay at Paris he translated into French a German memoir of Ritter on the pile à charger, or secondary pile, (Ladung's Säule). This translation, accompanied by notes on the experiments made by himself, was presented to the first class of the Institute and printed in the Journal de Physique, number for Brumaire, an XII, (1803.) Ritter, who had co-operated in the translation by an uninterrupted correspondence with Oersted, was fully satisfied with it, and even avowed that he comprehended himself in the French version better than in his own original German text. He died soon afterwards, and Oersted, independ*See Researches sur l'Indentité des Forces Chimiques et Électriques, by M. Oersted, translated from the German by M. Marcel de Serres, 1813, p. 10.

ently of his own original ideas, remained the representative and, in some sort, the heir of those of Ritter, of whom he had been the last collaborator and interpreter. Some prepossessions, whatever their origin, perhaps the fear of being received with a certain superciliousness, had led Oersted to pass almost the whole time of his sojourn in Paris without going to present to the celebrated Fourcroy, professor of chemistry at the Polytechnic School, a letter of professor Manthey, of Copenhagen. He decided at last to do so at the instance of the chargé d'affaires of Denmark. The elegance, the clearness, the authority with which Fourcroy discharged the functions of professor, gave him great ascendency over his pupils; but, out of the chair, he did not always sufficiently divest himself of the magisterial dignity. He congratulated the young and modest Oersted on having come to Paris and having acquired a knowledge of so many remarkable men, superior beyond doubt to all the chemists of the north. "I must acknowledge," replied Oersted, "that you possess at Paris more dexterity than exists elsewhere in chemical manipulations; but there is scarcely to be found in the north a single chemist who cannot read in the original the Système des connaissances chimiques of M. de Fourcroy, which few French chemists could do for works written in the Scandinavian languages." To the question, if he had seen the Polytechnic School, Oersted replied of course affirmatively, and Fourcroy having made him duly sensible that this school gave to Paris a great superiority over Denmark, Oersted rejoined, with perhaps too ingenuous a confidence: "I admit that my country wants much which is needed for the fruitful development of chemistry, but I do not despair of contributing hereafter to establish there something not unlike the Polytechnic School." Upon which, Fourcroy begged him, somewhat ironically, to be sure to preserve, when he returned home, a kind recollection of the French chemists. This Oersted did not fail to do, and I shall show further on how he proved it.

In returning to Denmark, Oersted traversed Holland, and, at Harlem, made a great number of electrical experiments with the learned physicist Van Marum. At Bremen he contracted a friendship with the astronomer Olbers, and with Treviranus, celebrated for his labors in physiology and comparative anatomy, and finally re-entered his country in the month of January, 1804. On his return, the duty, at first temporary and limited to three years, of delivering lectures on physics at the University of Copenhagen was confided to him; in 1806 he was named professor extraordinary of physics in the same university. He had here the first opportunity of combining his scientific views in a systematic shape, the outline of which he preserved during his entire life, only modifying certain parts according to the progress of science.

His lectures commanded a large attendance; they bore a form which was peculiar to himself. The skillful professor usually commenced in a subdued tone, with particular considerations and explanations; frequently, indeed, with the definition of certain expressions, turning on the translation of technical words into the Danish language. Assured thenceforth of being fully understood, he followed the logical course of ideas, and warming by degrees, collected the facts into groups, and these groups into a whole still more comprehensive. The animation of the lecture, in giving more freedom to his delivery, called forth his favorite thoughts on the unity, the beauty of nature, and figures and images presented themselves which keenly interested his auditors, especially the younger portion of them, for those who had already followed other lectures were more surprised at still finding something unusual in his.

It was sometimes objected to Oersted that he saw or imagined in nature combinations much more rational than those which can be expected to occur in an assemblage of material objects; but he replied that nothing is too rational to be attributed to the supreme reason which has created everything. On such a theme it would be easy to argue a long time without coming to an understanding. It would be to plunge into the depths of those German discussions in which so

many a subtle genius has exhausted itself without exhausting the subject. But the obscurity of these depths is sometimes quite à la mode on the shores, always a little foggy, of the Baltic sea.

It seems certain, however, that the lectures of Oersted were well received by the youth and the public of Copenhagen, for they were always much frequented, and they secured for the professor an eminent position among his fellow-citizens. He was not long in establishing agreeable relations with persons of the highest position in the capital of Denmark, and even with the princes of the royal family. But a part of his success might also be attributed to his lively and intellectual conversation, to the frequent articles which he put forth on various subjects, and to the works which he published at this epoch, such as his Considerations on the history of chemistry, his Experiments respecting the figures produced by nodal lines on vibrating surfaces, a subject to which Chladni had already devoted an important work; and a Discourse on the pleasure produced by sound, a discourse in which he developed, under a point of view peculiar to himself, the laws of the beautiful.

He thus continued to publish, as he had done from his youth, a multitude of memoirs and articles of more or less extent on different subjects relating to the natural sciences and to philosophy, all of which met with appreciative readers. Nevertheless, Copenhagen was not a center to which everything converged as is Paris or London. In a city of secondary importance one may keep himself informed of what is written, but the inconvenience is soon felt of not knowing what is talked about in the learned world. Oersted, who had need of direct communication with entire Europe, felt himself impelled to undertake new expeditions. He set out for Berlin May 7, 1812, where he passed three months and gave to the press, in the German language, one of his most important works, entitled "Views of the chemical laws of nature," (Ansichten der chemischen Naturgesetze.) In passing through Germany he visited Oken, Schweiger, and Hegel, and established friendly relations with the ingenious physicist Seebeck, who, some years afterwards, made the discovery of thermo-electricity. He then revisited Paris, where he made quite a long stay, and, about the middle of the year 1813, returned to Copenhagen, there to receive anew from his countrymen tokens of the cordial consideration which he had long before inspired.

In 1814 Oersted published, in the programme of the university, an essay on a chemical nomenclature common to all the Germano-Scandinavian languages. The names proposed were so happily appropriate to the genius of those tongues that they were generally adopted, and are still in use in all the countries of the north. In 1815 the Royal Society of Sciences of Copenhagen, having lost its excellent secretary, Bugge, Oersted was chosen to replace him, and, the same year, the King named him a chevalier of the order of Danebrog. Two years afterwards the university conferred on him the title of professor in ordinary, (professor ordinarius,) a title superior to that of professor extraordinary which he had borne for more than 10 years.

About this time Oersted undertook a remarkable series of experiments on the compressibility of water, and found almost exactly, though by new means of his own invention, the numbers which the celebrated English physicist Canton had obtained half a century before.

In 1818 and 1819 he undertook, with MM. Esmarch and Forschhanımer, explorations in the island of Bornholm, for the purpose of examining its geological constitution with reference to the working of the coal and iron ore which are found there, and he made these investigations the subject of several publications. This was the commencement of a geological study of Denmark, established on new scientific bases. Oersted, however, was unable to prosecute this operation, which, continued by M. Forschhammer, has given to Denmark the excellent geological chart well known to this Academy.

The journeys to Bornholm did not interrupt the habitual course of Oersted's

publications on science and philosophy. Among his memoirs on physics should be particularly cited one on the trough-battery, executed in conjunction with his friend, Professor Esmarch. Another work, entitled Principles of the New Chemistry, which appeared at Copenhagen in 1820, had been composed for the auditors of his course, with a view to placing within their reach the doctrines taught in his numerous writings on chemistry and electricity, and particularly in his Views of the chemical laws of nature. First printed at Berlin, as I have said, this exposition of his favorite ideas had been translated into French by M. Marcel de Serres, and published at Paris, in 1813, with the concurrence of its author and that of our distinguished colleague, M. Chevreul, under the title of Researches on the identity of chemical and electric forces, a title which clearly defined its object.

This learned and ingenious work, dedicated to the author of the Statique Chimique, our illustrious Berthollet, was in truth the principal fruit of the labors and meditations of Oersted from his earliest youth. A citation of some passages of this admirable book will suffice to give an idea of the profound and original views which had presided over its composition: The chemical part of the natural sciences," says Oersted, "is far from having attained the perfection which their mechanical part has reached, and cannot, like the latter' deduce from a small number of principles, already connected with one another, all the other principles; but it has been obliged to seek each particular proposition, each particular law, by means of experiments undertaken solely with that particular view. Now the greater part of these laws have hitherto so little enabled us to see the bonds which unite them, that it was necessary to be convinced, by general considerations, of the unity which exists in all the works of nature, in order not to be deceived as regards that unity.

"The actual state, in 1813, of the chemical part of the natural sciences might be compared to that of their mechanical part before Galileo, Descartes, Huyghens, and Newton had taught us to reduce the more compound movements to their most simple principles. Before these illustrious physicists, it is true, a great number of important facts were known, even some remarkable series of facts, but that great principle of unity to which science owes its present high degree of perfection had not yet been arrived at.

*

# *

Oersted saw this great principle of unity in the uniformity of the general laws of mechanics, and he found an example of the duality, which also he everywhere sought, in the two forces which concur in producing circular or curvilinear motion. To find examples of the confusion which had preceded the discovery of these forces, it is sufficient, he said, "to read what was written on the classification of motions by the celebrated Bacon, who, although a cotemporary of Galileo, still speaks of a violent and natural motion, and of so many other kinds of motions, which he knew no better how to reduce to a single principle than do the chemists at the present time know how to reduce the affinities of the alkalies, acids, earths, oxides, combustible bodies, and oxygen to one identical primitive action. *

"By referring all motions to their fundamental laws, the mechanical part of the natural sciences," adds Oersted, "has been raised to that present degree of perfection which embraces all the movements of the universe as one great mechanical problem, whose solution enables us to calculate in advance an infinitude of particular phenomena. In order to prepare the chemical part of the natural sciences for a like perfection, we must endeavor to reduce all chemical actions to the primitive forces which produce them; we shall then also be in a position to calculate all the chemical properties of the primitive forces and their laws. Thus, chemistry being only occupied with these properties, this whole science will be converted into a theory of forces, to which mathematics may be applied, and it will thereby acquire perhaps new capacities, like those which have been derived from the application of mathematics to movement.

*

# *

"The discoveries which have been made since the commencement of this century may so far contribute to advance chemistry towards this state of perfection that I have thought it would be useful" (it is still Oersted who speaks) "to collect here the scattered materials, in order to attempt the formation of a system. A first attempt of this kind can, doubtless, be but imperfect; but it must at last be necessary to take this first step, and I have judged it proper not to defer taking it, for the investigator of nature will make no great discovery except in so far as he shall have a certain idea which leads him to propound, so to say, his questions to nature, as well as a determinate scope for his observations. The object, therefore, of the system which we here present is chiefly to draw attention to certain important problems, and to serve as preliminary to other more perfect systems which the rapid progress of science will not fail soon to call forth. It is only by the united efforts of a great number of savants, and after some generations, that chemical science can attain that degree of perfection which, with perhaps too much boldness, we have ventured to anticipate.

"It will not be useless, at our first step in this undertaking, to cast a glance over the space which we shall have to traverse. We shall commence our researches by a general classification of all the inorganic bodies according to their chemical nature. We shall then present some considerations on the chemical actions best known, in order to prove that all the chemical phenomena which have been studied up to this time may be attributed to two forces diffused through all nature. We shall show that these forces act not only in the immediate contact between two bodies, but that they can also be transmitted, by some medium, from one to the other. This will lead us to discover, independently of electrical considerations, the chemical action which we have recognized in galvanism. By means of these successive approaches we shall be able finally to present the chemical forces in the state in which they are most free, and to render evident, at the same time, the identity of those forces with electrical forces."*

I should have abridged this long passage still more than I have done, had I not desired that it should be comprehended to what extent, according to Oersted, is to be found in the general uniformity of the laws of chemical composition that great principle of unity which, agreeably to his philosophical conceptions, exists in all nature, and, at the same time, the duality which he also sought there in the two electricities, positive and negative. "Finally," Oersted continues, "we shall endeavor, in order still better to prove the universality of the two chemical or electrical forces, to show that they also produce the magnetic phenomena and the principal changes in organic nature." These lines already contained, so to say, the programme of the great discovery which he was on the point of making. In this work, as in his earlier essays of 1799, Oersted placed aluminium in the rear of the alkaline earths, ‡ as less alkaline than all these latter, and indeed almost an acid. After aluminium came silicium, more acid than alkaline; while glass, he said, might be considered as a salt.§ It will be admitted that from thence to the theory of the silicates there was but a step; this new advance was achieved some time afterwards by Smithson Tennant; but, as every one knows, it was Berzelius, beyond all others, who developed the theory of the silicates.

The work of Oersted, which the limits prescribed to this notice do not permit me completely to analyze, contains a multiplicity of views; all equally marked by justness of thought, and more than one of which offers even at this day something of the piquancy of novelty.

In another passage, seeking to find among authors already become antiquesuch as Winterl, Ritter, &c.-the first rudiments of the ideas which occupied him, and which it was the object of his book to develop, Oersted added: "The * See Recherches sur l'identité des forces chimiques et électriques, p. 2.

+Ibid, p. 9.

+ Ibid., p. 57.

§ Ibid., p. 60.