One of the most interesting phenomena in connection with physical science is what is called the polarization of light. "If," says Sir D. Brewster, they felt that every moment's delay was bringing them into imminent jeopardy. In the meanwhile, a change had taken place in the government of Algiers; the new Dey, instead of continuing to M."we transmit a beam of the sun's light Arago the protection which his predecessor had so kindly granted, resolved upon securing his services as a slave, and he appointed him to the post of interpreter on board one of the cruisers which still infested the Mediterranean. The French consul had to exert all his influence, for the purpose of averting the danger which now threatened M. Arago from the quarter, where he had before found so much courtesy, and such ready assistance. At length the secretary of the Board of Longitudes finally left Africa, and after very narrowly escaping capture by an English vessel, he landed at Marseilles. So much labour, such perseverance, such devotedness to the interests of science, demanded and obtained an acknowledgment: the Institute for once infringed upon its own regulations, and elected M. Arago, although he was not yet twenty-three years old. He was also named to a professorship in the Ecole Polytechnique, and he delivered there a course of lectures upon geometry and analysis, which he continued till his début in the political career, during the parliamentary session of 1831. M. Arago attracted the notice of the Emperor, who was always more partial to scientific men than to littérateurs, or as he called them idéologues. It is very well known that when, after the battle of Waterloo, Napoleon thought of retiring to the United States, and there devoting his time exclusively to the pursuits of science, he intended to take with him Arago as his companion. This was no slight honour; a distinction of such a character must say much for the person upon whom it is conferred. We must now direct attention to the principal discoveries made by M. Arago in natural philosophy, and, in doing so, shall endeavour to be as concise, and at the same time as clear, as the subject will allow. The axioms or the deductions of electricity, for instance, cannot be made to read like a fashionable novel; and even whilst avoiding for mulæ and equations, we are conscious that a summary of scientific facts must seem comparatively dull. We shall do our best, however. through a circular aperture into a dark It is found that in all bodies where there seems to be a regularity of structure, as salts, crystallized minerals, all animal and vegetable bodies, on light passing through them, it is divided into the law of rotation of simple-coloured rays. His researches on that subject will be found in the Mémoires de l' Institut for 1812 and 1818. Circular polarization has discovered differences in the composition of substances that the utmost art of the analytical chemist could not detect; for, by this light, it is not the mere structure but the nature of the particles that is elucidated. Hence the construction of an instrument called the polariscope, which is used by the sugar manufacturer to ascertain the quantity of saccharine matter in the juice of the beet-root; by the brewer, to learn the amount of sugar in the wort; and by the medical professor, the extent of sugar in the secretions of the diabetic patient. two distinct pencils. Now, M. Arago observed, that when a polarized ray was made to traverse at right angles, a plate of rock crystal (quartz) cut perpendicularly to the axis of double refraction, on analyzing the emergent ray by a doubly refracting prism, the two images had complementary colours, and that these colours changed when the doubly refracting prism was made to revolve; so that, in the course of a half-revolution, the extraordinary image (for example) which at first was red, became in succession orange, yellow, yellow-green, and violet, after which the same series of tints would of course recur. It is evident that this is just what would take place, supposing the several coloured rays at this convergence from the rock crystal to be polarized in different planes; We turn now to another subdivision and to this conclusion M. Arago came. of natural philosophy, and will endeaHe wrote a couple of extremely inter-vour to say a few words concerning M. resting papers on what has since been Arago's investigations in the comparacalled the phenomena of circular polari- tively new science of electro-magnetism. zation, and read them before the Insti- We find his name here associated with tute, in the year 1811. those of Ampère and Biot in the development of a series of theories and ex fessor Oersted, of Copenhagen, was the first who described the analogies between magnetism and electricity. In 1819, by bringing a magnetic needle in the direction of a voltaic current, he ascertained that the conducting wire is itself magnetic. He found also that the nature of the conducting medium is immaterial to the result, and that whether the voltaic circuit be compelled through metals or through a fluid, the magnetic needle is equally affected; being deflected in one direction when placed over the conductor, and in the opposite direction when under it. New facts are constantly being added to the accumulated data of natural phi-periments singularly interesting. Prolosophy. M. Arago's discovery has consequently followed the general law, and been applied more extensively than it was at first; some of the most beautiful experiments that can be exhibited in the course of a scientific conversazione, are based upon the labours of the French philosopher, and very useful results have been deduced from what may appear at first glance a merely idle investigation. If with a plate of tourmaline we examine a polarized ray of white light, as it passes through a crystalized substance, having a single axis, there are seen rings of various prismatic colours, which change as the position of the tourmaline is altered. On the axis of the tourmaline being brought into the plane of polarization, a rich black cross is seen crossing the coloured rings; gradually, as the tourmaline is turned, the black cross fades away; and when in the opposite direction, the white one supplies its place, and the second image is complementary to the previous one. M. Biot resumed and investigated more thoroughly still the subject of rotatory or circular polarization, as introduced by his learned colleague. He observed the phenomena not only in solids but in liquids, such as oil of turpentine, alcohol, oil of laurel; and he ascertained The discovery was no sooner made known than all those who were engaged in scientific researches throughout Europe pursued the inquiry with diligence, and continually elicited additional facts, which bestowed increased importance on this branch of electric science. M. Arago's experiment is as follows. He strewed a quantity of iron filings on a table; then, after having connected by a wire the ends of a galvanic battery, he brought that connecting wire near the filings; they were immediately affected by the action of the battery, some few flying towards the wire and adhering to it as to a magnet; and if the wire was brought into actual contact with current is the only one which has secured for the electric telegraph all its efficiency. them, a very considerable quantity could be taken up by it, exactly the same as the extremity of a bar magnet; but the moment the contact was broken, the M. Arago's discoveries in the science filings fell. This fact proved, not only of magnetism were rewarded in England that the wire had the power of acting on by the gift of a gold medal presented to bodies already magnetized, but that it him in the year 1829. He was one of was itself capable of developing mag- the most eminent members of the netism in iron that did not previously Académie des Sciences, and besides a possess this power. The same attrac- variety of memoirs, reports, notices, tion took place with wires of brass, silver, éloges, etc., he had established, together platina, etc., and was so strong as to act with Gay-Lussac, a periodical well known on the filings when the wire was under the title, Annales de Physique et brought near them without actual con- Chimie. But upon his appointment to tact. It was shown not to belong to the Paris observatory as director and any permanent magnetism in the wire manager in chief, he struck into quite a or filings, by the inactivity of both when new path, and evinced in his duties as the connection was not made with the an astronomical lecturer powers equal, if battery; and it was proved not to be not superior, to those he had hitherto electrical attraction, by the connecting displayed. For M. Arago's writings on wire having no power over filings of magnetism, on light, on electricity, copper, or brass, or over saw dust. though remarkably suggestive and full When soft iron was used, the magnetism of interest for those who have already given was only momentary; but on re- mastered thoroughly the points dispeating the experiment with some modi-cussed, are comparatively of little value fication, M. Arago succeeded completely to the great generality of readers. You in magnetizing a sewing needle perma- must come to them prepared by a knownently. ledge of algebraic processes, and it is Without going farther into the sub-impossible to understand the complete ject, we may just notice that in the pro- bearing of any theory introduced, if you cess of the various investigations under- cannot follow it through all the expres taken by M. Arago he had the benefit sions of the mathematical language. of the directions and advice of the As a teacher of astronomy, on the concelebrated M. Ampère, whose labours as trary, M. Arago is pre-eminently a man a natural philosopher have ensured to for the masses. With him the reader him a European reputation. A spirit of should take for granted all the calcularivalry was aroused between the savans tions of Newton and Laplace. He should of various nations, and whilst the mem-admit theorems which others have setbers of the French Institute pursued tled for his benefit, and assent to the their researches with strenuous ardour, laws of the solar system with the most Sir Humphry Davy, Professor Faraday, childlike confidence. The great object and others in England endeavoured of a lecturer who treats astronomy as likewise to expand the facts discovered M. Arago treated it, is clearness in his by Oersted. exposition, and simplicity in his statements. He must not dazzle, he must not be afraid of repetitions, he must not think that homely illustrations and an un-scientific terminology are below his dignity. In that respect the only writer we would compare to M. Arago is the veteran Humboldt. Without for a moment wishing to disparage what we designate as scientific astronomy, we must allow that descriptive cosmography is at all events the only way of conveying to the minds of the majority truths which are still useful, still interesting, if even it cannot be seen how they have been elicited. After a long life devoted to the study of the heavens, when Ptolemy wrote on the walls of the temple It will appear evident to all those who consider the subject with the slightest care, that the invention of the electric telegraph follows as the natural consequence upon a knowledge of the laws which regulate electro-magnetism. No wonder, therefore, if M. Arago felt interested in the general application of a communicating medium which is likely to be so useful for the purposes of geography and physical science. He organized with Professor Airy, the Astronomer Royal, a plan for corresponding by means of electricity between Greenwich and Paris, and it may safely be affirmed that the method he introduced for obtaining a powerful magnetizing M. Arago gathered his hearers from all classes of society; - clerks, commercial men, mechanics, ladies even crowded around him; those who could not venture as far as the Observatoire, read his works and studied the year-book published under his superintendence by the Board of Longitudes. He thoroughly convinced all that a sufficient knowledge of astronomy is within the reach of the humblest individual; and that every one who does direct his attention to that science can contribute even by the most simple observations to its progress. of Serapis at Canopus, the principal that he is uniformly accurate. We have results of his labours, he enunciated noticed amongst other blunders a most descriptively the elements of the solar extraordinary one which disfigures the system. éloge of Condorcet prefixed, in 1847, to a magnificent reprint of that philosopher's complete works. Condorcet, it is well known, published an edition of Pascal's thoughts, for the express pur pose of proving that he was tainted with incurable scepticism. Comparing this edition with that given a short time after Pascal's death by the Messieurs de Port-Royal, M. Arago designates the latter as d'Arnaud's edition. Now, this cannot be a misprint, for the name d'Arnaud is twice repeated, and no erratum points it out as a blunder. We must conclude, therefore, that M. Arago, with all his leaning, managed to mistake the great divine, Antonio Arnaud, for a third-rate scribbler, Baculard d'Arnaud, who died in the year 1805! This, unfortunately, is not all. We are sorry to add that M. Arago felt it necessary to defend Condorcet on the most objectionable grounds. Condorcet was an infidel; we might pity him deeply for that, and still respect, to a great extent, a conscientious man struggling for spiritual life amidst the wrecks of his belief. But Condorcet may be described as an irreligious fanatic, who never scrupled to employ the vilest means in his attacks against Christianity. Condorcet was a Voltairian monomaniac, and that is the only excuse we can give for him. On the subject of religion he was non compos mentis. How can M. Arago have had the courage to stand by him in this indefensible position? How did he not perceive, that, whilst pronouncing a panegyric upon the mathematician and the writer, he was in no way compelled to carry his apology farther? Speaking of M. Arago brings naturally to our recollection the name of another writer well known in France as a popular writer on the same science; we allude to Fontenelle. His Entretiens sur le Pluralité des Mondes, published in 1686, was nothing else but a work destined to introduce the primary truths of astronomy in an attractive form before the inmates of drawing-rooms and the votaries of fashion. The lady who said one day that M. de Cassini would be kind enough to begin the eclipse over again if she was too late, was the type of Fontenelle's admirers. Our dandies now-a-days are not quite so ignorant, it must be confessed; they require a teacher a little more accurate than the affected predecessor of M. Arago in the secretaryship of the Académie des Sciences. Fontenelle, so to speak, dressed up Copernicus in the costume of Mademoiselle de Scudéry, in order to render him acceptable; M. Arago has only brought him within our reach. We have elsewhere remarked when speaking of Cuvier, the harmonious blending of the various elements which constitute the scientific investigator and the man of letters. M. Arago is another instance of the same fact. He does not, perhaps, write with the same power as the great naturalist; but his style is clear, and his imagination singularly brilliant. The life of Carnot, published not very long ago, is a masterly production: the writer found there a capital opportunity, not only for expounding scientific principles, but also for holding up for public admiration the great political doctrines applied by the French Revolution. But, if M. Arago is always interesting as a writer, we cannot say In 1831, M. Arago took his seat in the chamber, of deputies, and distinguished himself throughout his parliamentary career as one of the leaders on the opposition benches. Some of the speeches he delivered are masterpieces, and we would particularly allude to that pronounced when the bill for the construction of the forts round Paris was under discussion. The following passage from M. de Cormenin's Livre des Orateurs contains, we believe, a very fair appreciation of M. Arago's oratorical powers: Whenever Arago ascends the tribune, the chamber, attentive and anxious, be comes still, and listens eagerly. The spectators hang over the galleries to see him. His stature is lofty, his hair is naturally curled and flowing, and his fine southern head rises over the assembly. In the muscular contractions of his temples there is a power of will and of thought which reveals a noble spirit. Unlike those speakers who address the house on every occasion, and who, nine times out of ten, are ignorant of what they talk about, Arago does not speak except on questions already prepared, and which combine the interest of the circumstance with the attractions of science. His speeches are, therefore, quite to the purpose as well as general, and appeal at once to the reason and the passions of his auditory. In this manner he soon comes to master them. The very moment he enters on his subject, he concentrates on himself the eyes and the attention of all. He takes science, as it were, between his hands; he strips it of asperities and its technical forms, and he renders it so clear that the most ignorant are astonished, as they are charmed at the ease with which they understand its mysteries. There is something perfectly lucid in his demonstrations. His manner is so expressive that light seems to issue from his eyes, from his lips, from his very fingers. He interweaves in his discourse the most caustic appeals to ministers-appeals which defy all answer; the most piquant anecdotes, which seem to belong naturally to the subject, and which adorn without overloading it. When he confines himself to the narration of facts, his elocution has all the graces of simplicity. But, when he is, as it were, face to face with science, he looks into its very depths, draws forth its inmost secrets, and displays all its wonders; he invests his admiration of it with the most magnificent language, his expressions become more and more ardent, his style more coloured, and his eloquence is equal to the grandeur of his subject. When the events of 1848 once more brought to a crisis the destinies of France, M. Arago joined heartily in the republican movement. He became a member of the Provisional Government, and subsequently minister of marine. But he never entertained the least sympathy for the Red party, and when he saw that the opinions of Ledru Rollin and Louis Blanc were likely to prevail, he began to despair of republican institutions, in so far, at least, as they were applicable to his own country. During the terrible days of June, he took an active part against the insurgents, at the head of the national guard. After December, 1852, M. Arago felt that he could not hold any post under a ruler for whom he had no respect; he sent in his resignation. Louis Napoleon very generously refused it, and dispensed with the veteran astronomer's taking the oath of obedience to the new imperialist dynasty. M. Arago then devoted himself exclusively to science, and determined to wear out the remaining portion of his life in the pursuit of those studies which had procured for him his greatest reputation. But disease was already hard at work upon his constitution, and every throe of the moral agony under which France was writhing found a corresponding echo in his patriotic mind. He gradually sank without any hope of recovery, and, after a journey to the South, from which he only derived a temporary benefit, breathed his last on Sunday, the 2nd of October, 1853. It is melancholy to notice that, of the men who rose into political notoriety with the revolution of 1848, two already have carried to the grave their blighted hopes and bitter disappointments. Armand Marrast and Arago have paid dearly for their political experience. G. M. JOSEPH SMITH. "THE Mormon Prophet an illustrious man!" We can fancy the exclamation as the eye glances on his name, and will not attempt to parry its force by elaborate quibbling. If ignorance, raising itself from obscurity to promulgate its opinions throughout the world-if perseverance in the face of severe persecution and zeal, despite numerous obstacles, that issues in success and stamps its |