«Sir, you are inclined to punish me simply because I have by nature the gift of languages. I readily learn the dialects of the various countries where I carry on my trade. For example, I know the dialect of Iviza.' <<<Well, I will take you at your word. Here is a soldier who comes from Iviza. Talk to him.' «Very well; I will even sing the goat-song.' "The verses of this song (if one may call them verses) are separated by the imitated bleatings of the goat. I began at once, with an audacity which even now astonishes me, to intone the song which all the shepherds in Iviza sing: Ah graciada Señora, No sera gaiva pulida, Bè bè bè bè. "Upon which my Ivizan avouches, in tears, that I am certainly from Iviza. The song had affected him as a Switzer is affected by the 'Ranz des Vaches. I then said to the officer that if he would bring to me a person who could speak French, he would find the same embarrassment in this case also. An emigré of the Bourbon regiment comes forward for the new experiment, and after a few phrases affirms without hesitation that I am surely a Frenchman. The officer begins to be impatient. «Have done with these trials: they prove nothing. I require you to tell me who you are.' "My foremost desire is to find an answer which will satisfy you. the son of the innkeeper at Mataro.' "I know that man: you are not his son.' I am «You are right: I told you that I should change my answers till I found one to suit you. I am a marionette player from Lerida.' "A huge laugh from the crowd which had listened to the interrogatory put an end to the questioning." Finally it was necessary for Arago to declare outright that he was French, and to prove it by his old servant Pablo. To supply his immediate wants he sold his watch; and by a series of misadventures this watch subsequently fell into the hands of his family, and he was mourned in France as dead. After months of captivity the vessel was released, and the prisoner set out for Marseilles. A fearful tempest drove them to the harbor of Bougie, an African port a hundred miles east of Algiers. Thence they made the perilous journey by land to their place of starting, and finally reached Marseilles eleven months after their voyage began. Eleven months to make a journey of four days! The intelligence of the safe arrival, after so many perils, of the young astronomer, with his packet of precious observations, soon reached Paris. He was welcomed with effusion. Soon afterward (at the age of twenty-three years) he was elected a member of the section of Astronomy of the Academy of Sciences, and from this time. forth he led the peaceful life of a savant. He was the Director of the Paris Observatory for many years; the friend of all European scientists; the ardent patron of young men of talent; a leading physi.cist; a strong Republican, though the friend of Napoleon; and finally the Perpetual Secretary of the Academy. In the latter capacity it was part of his duty to prepare éloges of deceased Academicians. Of his collected works in fourteen volumes, 'Œuvres de François Arago,' published in Paris, 1865, three volumes are given to these 'Notices Biographiques.' Here may be found the biographies of Bailly, Sir William Herschel, Laplace, Joseph Fourier, Carnot, Malus, Fresnel, Thomas Young, and James Watt; which, translated rather carelessly into English, have been published under the title 'Biographies of Distinguished Men,' and can be found in the larger libraries. The collected works contain biographies also of Ampère, Condorcet, Volta, Monge, Porson, Gay-Lussac, besides shorter sketches. They are masterpieces of style and of clear scientific exposition, and full of generous appreciation of others' work. They present in a lucid and popular form the achievements of scientific men whose works have changed the accepted opinion of the world, and they give general views not found in the original writings themselves. Scientific men are usually too much engrossed in advancing science to spare time for expounding it to popular audiences. The talent for such exposition is itself a special one. Arago possessed it to the full, and his own original contributions to astronomy and physics enabled him to speak as an expert, not merely as an expositor. The extracts are from his admirable estimate of Laplace, which he prepared in connection with the proposal, before him and other members of a State Committee, to publish a new and authoritative edition of the great astronomer's works. The translation is mainly that of the 'Biographies of Distinguished Men' cited above, and much of the felicity of style is necessarily lost in translation; but the substance of solid and lucid exposition from a master's hand remains. Arago was a Deputy in 1830, and Minister of War in the Provisional Government of 1848. He died full of honors, October 2d, 1853. Two of his brothers, Jacques and Étienne, were dramatic authors of Another, Jean, was a distinguished general in the service of Mexico. One of his sons, Alfred, was favorably known as a painter; another, Emmanuel, as a lawyer, deputy, and diplomat. note. Edward S. Holden THE LAPLACE HE Marquis de Laplace, peer of France, one of the forty of the French Academy, member of the Academy of Sciences and of the Bureau of Longitude, Associate of all the great Academies or Scientific Societies of Europe, was born at Beaumont-en-Auge, of parents belonging to the class of small farmers, on the 28th of March, 1749; he died on the 5th of March, 1827. The first and second volumes of the 'Mécanique Céleste' [Mechanism of the Heavens] were published in 1799; the third volume appeared in 1802, the fourth in 1805; part of the fifth volume was published in 1823, further books in 1824, and the remainder in 1825. The 'Théorie des Probabilités' was published in 1812. We shall now present the history of the principal astronomical discoveries contained in these immortal works. Astronomy is the science of which the human mind may justly feel proudest. It owes this pre-eminence to the elevated nature of its object; to the enormous scale of its operations; to the certainty, the utility, and the stupendousness of its results. From the very beginnings of civilization the study of the heavenly bodies and their movements has attracted the attention of governments and peoples. The greatest captains, statesmen, philosophers, and orators of Greece and Rome found it a subject of delight. Yet astronomy worthy of the name is a modern science: it dates from the sixteenth century only. Three great, three brilliant phases have marked its progress. In 1543 the bold and firm hand of Copernicus overthrew the greater part of the venerable scaffolding which had propped the illusions and the pride of many generations. The earth ceased to be the centre, the pivot, of celestial movements. Henceforward it ranged itself modestly among the other planets, its relative importance as one member of the solar system reduced almost to that of a grain of sand. Twenty-eight years had elapsed from the day when the Canon of Thorn expired while holding in his trembling hands the first copy of the work which was to glorify the name of Poland, when Würtemberg witnessed the birth of a man who was destined to achieve a revolution in science not less fertile in consequences, and still more difficult to accomplish. This man was Kepler. Endowed with two qualities which seem incompatible,- a volcanic imagination, and a dogged pertinacity which the most tedious calculations could not tire,- Kepler conjectured that celestial movements must be connected with each other by simple laws; or, to use his own expression, by harmonic laws. These laws he undertook to discover. A thousand fruitless attempts-the errors of calculation inseparable from a colossal undertakingdid not hinder his resolute advance toward the goal his imagination descried. Twenty-two years he devoted to it, and still he was not weary. What are twenty-two years of labor to him who is about to become the lawgiver of worlds; whose name is to be ineffaceably inscribed on the frontispiece of an immortal code; who can exclaim in dithyrambic language, "The die is cast: I have written my book; it will be read either in the present age or by posterity, it matters not which; it may well await a reader since God has waited six thousand years for an interpreter of his works"? These celebrated laws, known in astronomy as Kepler's laws, are three in number. The first law is, that the planets describe ellipses around the sun, which is placed in their common focus: the second, that a line joining a planet and the sun sweeps over equal areas in equal times; the third, that the squares of the times of revolution of the planets about the sun are proportional to the cubes of their mean distances from that body. The first two laws were discovered by Kepler in the course of a laborious examination of the theory of the planet Mars. A full account of this inquiry is contained in his famous work, 'De Stella Martis' [Of the Planet Mars], published in 1609. The discovery of the third law was announced to the world in his treatise on Harmonics (1628). To seek a physical cause adequate to retain the planets in their closed orbits; to make the stability of the universe depend on mechanical forces, and not on solid supports like the crystalline spheres imagined by our ancestors; to extend to the heavenly bodies in their courses the laws of earthly mechanics, such were the problems which remained for solution after Kepler's discoveries had been announced. Traces of these great problems may be clearly perceived here and there among ancient and modern writers, from Lucretius and Plutarch down to Kepler, Bouillaud, and Borelli. It is to Newton, however, that we must award the merit of their solution. This great man, like several of his predecessors, imagined the celestial bodies to have a tendency to approach each other in virtue of some attractive force, and from the laws of Kepler he deduced the mathematical characteristics of this force. He extended it to all the material molecules of the solar system; and developed his brilliant dis covery in a work which, even at the present day, is regarded as the supremest product of the human intellect. The contributions of France to these revolutions in astronomical science consisted, in 1740, in the determination by experi ment of the spheroidal figure of the earth, and in the discovery of the local variations of gravity upon the surface of our planet. These were two great results; but whenever France is not first in science she has lost her place. This rank, lost for a moment, was brilliantly regained by the labors of four geometers. When Newton, giving to his discoveries a generality which the laws of Kepler did not suggest, imagined that the different planets were not only attracted by the sun, but that they also attracted each other, he introduced into the heavens a cause of universal perturbation. Astronomers then saw at a glance that in no part of the universe would the Keplerian laws suffice for the exact representation of the phenomena of motion; that the simple regular movements with which the imaginations of the ancients were pleased to endow the heavenly bodies must experience numerous, considerable, perpetually changing perturbations. To discover a few of these perturbations, and to assign their nature and in a few rare cases their numerical value, was the object which Newton proposed to himself in writing his famous book, the 'Principia Mathematica Philosophiæ Naturalis' [Mathematical Principles of Natural Philosophy]. Notwithstanding the incomparable sagacity of its author, the 'Principia' contained merely a rough outline of planetary perturbations, though not through any lack of ardor or perseverance. The efforts of the great philosopher were always superhuman, and the questions which he did not solve were simply incapable of solution in his time. Five geometers-Clairaut, Euler, D'Alembert, Lagrange, and Laplace shared between them the world whose existence Newton had disclosed. They explored it in all directions, penetrated into regions hitherto inaccessible, and pointed out phenomena hitherto undetected. Finally and it is this which constitutes their imperishable glory-they brought under the domain of a single principle, a single law, everything that seemed most occult and mysterious in the celestial movements. Geometry had thus the hardihood to dispose of the future, while the centuries as they unroll scrupulously ratify the decisions of science. |