Page:Encyclopædia Britannica, Ninth Edition, v. 9.djvu/508

476 F O U F IT After an education received chiefly at home, he studied medicine, which, however, he speedily abandoned for physical science, the improvement of Daguerre s photo graphic processes being the object to which he first directed his attention. During three years he was experimental assistant to M. Donne" in his course of lectures on micro scopic anatomy. With M. Fizeau he carried on a series of investigations on the intensity of the light of the sun, as compared with that of carbon heated in the voltaic arc, and of lime in the flame of the oxyhydrogen blowpipe ; on the interference of heat rays, and of light rays differing greatly in lengths of path ; and on the chromatic polariza tion of light. In 1849 he contributed to the Comptes Rendus of the Academy of Sciences, t. xxviii., a description of an electromagnetic regulator for the electric lamp, and, in conjunction with Regnault, a paper on binocular vision. By the use of a revolving mirror similar to that used by Wheatstone for measuring the rapidity of electric currents, but having a concave mirror centred in its axis, he was enabled in 1850 to demonstrate the greater velocity of light in air than in water, and to establish the law deduced from the undulatory theory that the velocity of light in different media is inversely as the refractive indices of the media. In the same year he was created a chevalier of the Legion of Honour. For his demonstration in 1851 of the diurnal motion of the earth by the rotation of the plane of oscillation of a freely suspended, long, and heavy pendulum in an E.S.W, direction, exhibited by him at the Pantheon in Paris, and again in the following year by means of his invention the gyroscope, he in 1855 received the Copley medal of the Royal Society of London, He was also in 1855 made physical assistant in the imperial observatory at Paris. In September of that year he discovered that the force required for the rotation of a copper disc moving in its own plans becomes greater, the disc at the same time growing hotter, when the disc is made to rotate with its rim between the poles of a horse-shoe magnet. Foucault invented in 1857 the polarizer which bears his name, and in the succeeding year a method of giving to the speculum of reflecting telescopes the form of a spheroid or a para boloid of revolution. His reflector for the great telescope in ths Paris observatory was mounted in June 1859. With Wheatstone s revolving mirror he in 1862 deter mined the absolute velocity of light to be 298,000 kilometres (about 185,000 miles) a second, or 10,000 kiloni. less than that obtained by previous experimenters. He was created in that year a member of the Bureau des Longitudes and an. officer of the Legion of Honour, in 1864 a foreign member of the Royal Society of London, and next year a member of the Mechanical Section of the Institute. In 1805 appeared his papers on a modification of Watt s governor, upon which he had for some time been experiment ing with a view to making its period of revolution constant, and on a new apparatus for regulating the electric light ; and in the following year (Compt. Rend. Ixiii. ) he showed how, by the deposition of a transparently thin film of silver on the outer side of the object glass of a telescope, the sun could be viewed without injuring the eye by excess of light. Foucault died of paralysis, February 11, 1868. From the year 1815 he edited the scientific portion of the Journal des Debats. His chief scientific papers are to be found in the Comptes Rendus, t. xxv., 1847 Ixix., 1869. See Revue Cours Sclent, vi., 1869, pp. 484-489; Proc. Roy. Soc. xvii., 1869, pp. Ixxxiii.-lxxxiv. ; Lissayous, Notice historiquc sur la vie ct les travaux de Leon Foucault, Paris, 1875. FOUCHE, JOSEPH (1763-1820), duke of Otranto, minister of police under Napoleon I., was born in a small village near Nantes, 26th May 1763. He was the son of a ship captain, and at the age of nine years began the study of mathematics at the college of his native place, with the view of entering the merchant marine. That such a call ing would have proved congenial to him is not very probable, and at any rate it presented so little attraction to his youthful fancy that he induced his father to consent to the abandonment of this intention, and to permit him to continue his studies at Paris under the superintendence of the principal of the oratory. He afterwards taught successively in the colleges of Juilly, Arras, and Vendume ; and at the time of the Revolution he was prefet des etudes at Nantes. He now renounced his connexion with the ecclesiastical profession, and in 1792 succeeded in being- chosen one of the national deputies for Loire-Inferieure. In this capacity he made a violent speech in support of the execution of Louis XVI., without respite and without appeal to the people, taunting those who hesitated to adopt such an extreme measure with "trembling before the shade of a king." In the midst of the political chaos he determined to " ride on the whirlwind and direct the storm :" though he had little or no interest in moral speculation, he became an ardent asserter of atheism; and, though devoid of all political predilections, and actuated in his political purposes simply by a cool calculation of advantages that was seldom if ever surprised or ruffled even by the most critical contingencies, he soon manifested a zeal for republicanism which exceeded that of the wildest enthusiasts of that exceptional time. Having at the end of 1793 been commissioned to put in operation the law des suspects in the department of Nievre, then one of the centres of the royalist sympathizers, he not only succeeded in completely crushing all insurrectionary symptoms, but initiated the movement for the spoliation of the churches, by which the treasury was supplied with money for the campaign of 1794; and he also further inaugurated the age of reason by suppressing the priests and causing to be inscribedouthe doors of the cemeteries a sentence afterwards generally adopted for this purpose La mort est un sommeil cternel. In November of the same year he was appointed, along with Collot d Herbois, to execute the decree of the convention against the royalist city of Lyons; and here he vied with his colleague in a mania for destruction and bloodshed, inditing bombastic regrets that the mine and the guillotine did their work too slowly to accord with the impatience of the republic, or to express the omnipotence of the people. This devoted enthusiasm for freedom led to his being elected president of the Jacobin Club, 4th June 1794, soon after his return to Paris. He now so far allowed his audacity to overcome his discretion as to make some derisive allusions to the part played in the fete de 1 Etre Supreme by Robespierre, who on that account denounced him as an impostor and peculator, and procured his exp.il.sion from the society. Fouche had erred, however, only by a too quick anticipation of public opinion, for the execution of Robespierre fol lowed on the 25th July. The star of Fouche^ was thus for a short time again in the ascendant ; but having awakened distrust by some new intrigues, lie was denounced as a terrorist, expelled the convention 9th August 1795, and placed under arrest. He obtained his freedom by the amnesty of the 26th October following; and having obtained the confidence of the socialist Babeuf, and revealed his conspiracy to Barras, then president of the directory, lie was rewarded by an interest in the contracts of the army, and by being appointed in 1798 ambassador to the Cis alpine republic. Soon afterwards his intrigues against the directory of Milan led to his recall, but when the party of Barras again came into power he was appointed to the Hague. There he remained only a few months, returning to Paris to enter upon his famous career as minister of police, In this capacity he for some years exercised an influence on the internal affairs of France perhaps greater than that of