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 tired, however, of the lighter muse, and in 1774, to Gleim’s grief, left Halberstadt, and for two years (1774–1776) edited at Düsseldorf the Iris, a quarterly for women readers. Meanwhile, he wrote many charming lyrics, distinguished by exquisite taste and true poetical feeling. In 1784 he became professor of literature at the university of Freiburg im Breisgau, a post which he held until his death there on the 4th of January 1814. In addition to the earlier Iris, to which Goethe, his brother F. H. Jacobi, Gleim and other poets contributed, he published, from 1803–1813, another periodical, also called Iris, in which Klopstock, Herder, Jean Paul, Voss and the brothers Stollberg also collaborated.

Jacobi’s Sämmtliche Werke were published in 1774 (Halberstadt, 3 vols.). Other editions appeared at Zürich in 1807–1813 and 1825. See Ungedruckte Briefe von und an Johann Georg Jacobi (Strassburg, 1874); biographical notice by Daniel Jacoby in ''Allg. Deutsche Biographie; Longo, Laurence Sterne und Johann Georg Jacobi'' (Vienna, 1898); and Leben J. G. Jacobis, von einem seiner Freunde (1822).

JACOBI, KARL GUSTAV JACOB (1804–1851), German mathematician, was born at Potsdam, of Jewish parentage, on the 10th of December 1804. He studied at Berlin University, where he obtained the degree of doctor of philosophy in 1825, his thesis being an analytical discussion of the theory of fractions. In 1827 he became extraordinary and in 1829 ordinary professor of mathematics at Königsberg, and this chair he filled till 1842, when he visited Italy for a few months to recruit his health. On his return he removed to Berlin, where he lived as a royal pensioner till his death, which occurred on the 18th of February 1851.

His investigations in elliptic functions, the theory of which he established upon quite a new basis, and more particularly his development of the theta-function, as given in his great treatise Fundamenta nova theoriae functionum ellipticarum (Königsberg, 1829), and in later papers in Crelle’s Journal, constitute his grandest analytical discoveries. Second in importance only to these are his researches in differential equations, notably the theory of the last multiplier, which is fully treated in his Vorlesungen über Dynamik, edited by R. F. A. Clebsch (Berlin, 1866). It was in analytical development that Jacobi’s peculiar power mainly lay, and he made many important contributions of this kind to other departments of mathematics, as a glance at the long list of papers that were published by him in Crelle’s Journal and elsewhere from 1826 onwards will sufficiently indicate. He was one of the early founders of the theory of determinants; in particular, he invented the functional determinant formed of the n2 differential coefficients of n given functions of n independent variables, which now bears his name (Jacobian), and which has played an important part in many analytical investigations (see ). Valuable also are his papers on Abelian transcendents, and his investigations in the theory of numbers, in which latter department he mainly supplements the labours of K. F. Gauss. The planetary theory and other particular dynamical problems likewise occupied his attention from time to time. He left a vast store of manuscript, portions of which have been published at intervals in Crelle’s Journal. His other works include Commentatio de transformatione integralis duplicis indefiniti in formam simpliciorem (1832), Canon arithmeticus (1839), and Opuscula mathematica (1846–1857). His Gesammelte Werke (1881–1891) were published by the Berlin Academy.

See Lejeune-Dirichlet, “Gedächtnisrede auf Jacobi” in the Abhandlungen der Berliner Akademie (1852).

JACOBINS, THE, the most famous of the political clubs of the French Revolution. It had its origin in the Club Breton, which was established at Versailles shortly after the opening of the States General in 1789. It was at first composed exclusively of deputies from Brittany, but was soon joined by others from various parts of France, and counted among its early members Mirabeau, Sieyès, Barnave, Pétion, the Abbé Grégoire, Charles and Alexandre Lameth, Robespierre, the duc d’Aiguillon, and La Revellière-Lépeaux. At this time its meetings were secret and little is known of what took place at them. After the émeute of the 5th and 6th of October the club, still entirely composed of deputies, followed the National Assembly to Paris, where it rented the refectory of the monastery of the Jacobins in the Rue St Honoré, near the seat of the Assembly. The name “Jacobins,” given in France to the Dominicans, because their first house in Paris was in the Rue St Jacques, was first applied to the club in ridicule by its enemies. The title assumed by the club itself, after the promulgation of the constitution of 1791, was Société des amis de la constitution séants aux Jacobins à Paris, which was changed on the 21st of September 1792, after the fall of the monarchy, to Société des Jacobins, amis de la liberté et de l’égalité. It occupied successively the refectory, the library, and the chapel of the monastery.

Once transferred to Paris, the club underwent rapid modifications. The first step was its expansion by the admission as members or associates of others besides deputies; Arthur Young was so admitted on the 18th of January 1790. On the 8th of February the society was formally constituted on this broader basis by the adoption of the rules drawn up by Barnave, which were issued with the signature of the duc d’Aiguillon, the president. The objects of the club were defined as (1) to discuss in advance questions to be decided by the National Assembly; (2) to work for the establishment and strengthening of the constitution in accordance with the spirit of the preamble (i.e. of respect for legally constituted authority and the rights of man); (3) to correspond with other societies of the same kind which should be formed in the realm. At the same time the rules of order and forms of election were settled, and the constitution of the club determined. There were to be a president, elected every month, four secretaries, a treasurer, and committees elected to superintend elections and presentations, the correspondence, and the administration of the club. Any member who by word or action showed that his principles were contrary to the constitution and the rights of man was to be expelled, a rule which later on facilitated the “purification” of the society by the expulsion of its more moderate elements. By the 7th article the club decided to admit as associates similar societies in other parts of France and to maintain with them a regular correspondence.

This last provision was of far-reaching importance. By the 10th of August 1790 there were already one hundred and fifty-two affiliated clubs; the attempts at counter-revolution led to a great increase of their number in the spring of 1791, and by the close of the year the Jacobins had a network of branches all over France. It was this widespread yet highly centralized organization that gave to the Jacobin Club its formidable power.

At the outset the Jacobin Club was not distinguished by extreme political views. The somewhat high subscription confined its membership to men of substance, and to the last it was—so far as the central society in Paris was concerned—composed almost entirely of professional men, such as Robespierre, or well-to-do bourgeois, like Santerre. From the first, however, other elements were present. Besides Louis Philippe, duc de Chartres (afterwards king of the French), liberal aristocrats of the type of the duc d’Aiguillon, the prince de Broglie, or the vicomte de Noailles, and the bourgeois who formed the mass of the members, the club contained such figures as “Père” Michel Gérard, a peasant proprietor from Tuel-en-Montgermont, in Brittany, whose rough common sense was admired as the oracle of popular wisdom, and whose countryman’s waistcoat and plaited hair were later on to become the model for the Jacobin fashion. The provincial branches were from the first far more democratic, though in these too the leadership was usually in the hands of members of the educated or propertied classes. Up to the very eve of the republic, the club ostensibly supported the monarchy; it took no part in the petition of the 17th of July 1790 for the king’s dethronement; nor had it any official share even in the insurrections of the 20th of June and the 10th of August 1792; it only formally recognized the republic on the 21st of September. But the character and extent of the club’s influence cannot be gauged by its official acts alone, and long before it emerged as the principal focus of the Terror, its character had been profoundly changed by the secession of its more moderate elements, some to found the Club of 1789, some in 1791—among them Barnave, the Lameths, Duport and Bailly—to