796 DEMONOLOGY tion of psalms, litanies, prayers, and adjura- tions, are used to expel the evil spirits who by divine permission, it is believed, not only tempt the soul, but sometimes also possess the body. At the time of the reformation, the power of casting out devils was claimed, like the power of working miracles, as one of the tests of the Catholic church, and the Jesuits denied that heretical teachers had ever exhibited such power. There was also a popular belief in charms and talismans. To attribute certain nervous maladies and mysterious diseases to demoniacal agency has been as universal as the belief in demons. The phenomenon of preter- natural and involuntary activity is often pre- sented, followed by a cataleptic or trance-like state. The mania is often contagious, con- straining the beholder, by a sort of fascination, to become an actor. At the commencement of our era this belief was general throughout the known world, and was recognized in the Gospels, where Christ is represented as casting out demons. Avicenna first designates as ly- canthropia the madness of men who lie hid by day, and howl about graves and deserts in the night, and will not be persuaded that they are not wolves. This hallucination spread through the whole of central and southern Europe. Voltaire relates that in the district of the Jura, between 1598 and 1600, more than 600 lycanthropes were put to death by a single judge. Amid the festivities of midsummer day at Aix-la-Chapelle, in 1374, a large troop of men and women from the adjacent country rushed into the city, and in the public squares and churches danced in circles with the utmost violence for hours together, apparently uncon- scious of the presence of spectators, till at last they sank to the ground exhausted, groaning fearfully. In this state they professed to see visions of good and evil spirits, whose names they shouted out. Incredulous spectators, who came to witness the phenomenon, were themselves seized with an irresistible im- pulse, and danced and became ecstatic in their turn. The epidemic spread in a few months through the Netherlands and the Rhenish provinces, and exorcism was power- less. The dances were performed in honor of St. John, and were designated accordingly {chorea Sancti Johannis). The authorities of the Rhenish provinces having decided to ban- ish every person who was attacked, the dis- ease soon subsided. It reappeared at Stras- burg in 1418, and the afflicted, according to Paracelsus, could do nothing but dance until they were dead or cured. Sufferers entitled this malady St. Yitus's dance (chorea Sancti Viti), and were accustomed to appeal to that saint for healing. The disease continued in Germany, and Paracelsus boasts of the number he had cured. About the middle of the 15th century a rumor spread through the Pays de Vaud that the environs of Bern and Lausanne were filled with sorcerers and cannibals. Per- sons being arrested and tortured confessed that DE MORGAN they were possessed by devils, and great num- bers of them were executed. In 1549 many of the inhabitants of Artois were charged with sorcery, and confessed not only the murder and bewitching of infants and adults, but also participation in the orgies of the sabbat and association with the horrible incubi and suc- cubi. In spite of tortures and burnings, the epidemic of bewitchment spread before the close of the century through Mentz, Treves, Ravensburg, Constance, and Salzburg. In 1491 the nuns of Cambrai were seized with demonomania, and for four years ran like dogs across the country, sprang into the air like birds, climbed trees like cats, hung on the branches, imitated the cries of animals, and divined hidden things. At last the exorcists forced the devil to confess himself the cause of these things. The schools, convents, and nunneries were long favorite localities of the malady, which in these assumed its most hys- terical forms. (See WITCHCRAFT.) Among the best treatises on the subject are: Horst, Ddmonomagie (Frankfort, 1817) ; Ukert, Uebcr Damonen, Heroen und Genien (Leipsic, 1850); Bodin, Demonomanie (Paris, 1579) ; Colin de Plancy, Dictionnaire infernal (3d ed., Paris, 1844) ; Sir Walter Scott, "Letters on Demonol- ogy and Witchcraft " (1830) ; Catharine Crowe, " The Nightside of Nature " (London, 1848) ; Henry Christmas, " The Phantom World " (London, 1850) ; " The Occult Sciences " (Lon- don, 1855) ; and Michelet, La sorciere (Brus- sels, 1862). DE MORGAN, Augustus, an English mathemati- cian, born on the island of Madura, East Indies, in 1806, died in London, March 18, 1871. His father was an officer in the British army, and he was educated at Trinity college, Cambridge, where he graduated in 1827. He had begun his studies for the bar when, in 1828, on the foundation of the university of London, he was appointed professor of mathematics in that institution. He resigned this post in 1831, but returned to it on the death of his successor in 1836, and retained it till 1866, when he again resigned. He was a frequent contributor to the "Penny Cyclopedia," the "Athenaaum," and other periodicals, and to the transactions of various learned societies of which he was a member. He published " Elements of Arith- metic " (1830), " Elements of Algebra " (1835), " Connection of Number and Magnitude " (1836), "Elements of Trigonometry" (1837), " Essay on Probabilities " (1838), "Differential and Integral Calculus " (1842), " Formal Logic " (1847), "Arithmetical Books" (1847), "Trig- onometry and Double Algebra" (1849), and "Book of Almanacs" (1851). The work on "Formal Logic" gave rise to a controversy with Sir William Hamilton, as to which of them was the discoverer of a new principle in the theory of syllogisms. The "Arithmetical Books " gives the bibliography of the subject from the time of the invention of printing. The "Book of Almanacs" furnishes means by
