IROQUOIS, one of the most intelligent branches of the North American Indians, comprised a confederation of five, afterwards six, tribes, among whom the leading place was taken by the Mohawks; their territory lay inland in what is now New York State and the basin of the St. Lawrence.  Numbering some 25,000, they maintained their own against the hereditary foes by whom they were surrounded; they took kindly to English and Dutch settlers, but were hostile to the French, and in the wars of the 18th century were allies of England against the French; their descendants, about 12,000, in reservations in Canada and New York are a peaceful people, have accepted English religion and culture, and have proved themselves skilful and industrious agriculturists.

IRREDUCIBLE CASE, name given to a cubic equation which cannot be solved by the rule of CARDAN (q. v.).

IRTISH, an enormous river of Western Siberia and chief tributary of the Obi; its course from the Altai Mountains runs NW. through the Siberian plains for 1200 m.; it is navigable almost all the way in summer, and in winter it is a highway for sledge traffic; on its banks stand Semipalatinsk, Omsk, and Tobolsk.

IRVING, EDWARD, a great pulpit orator, born in Annan, Dumfriesshire; bred for the Scotch Church, became in 1819 assistant to Dr. Chalmers in Glasgow, and removed in 1822 to the Caledonian Church, London, where he attracted to his preaching the world of fashion as well as intellect in the city, who soon grew tired of him and left him, after which he took to extravagances which did not draw them back, and drew around him instead a set of people more fanatical than himself, and whose influence over him, to which he weakly yielded, infatuated him still more; the result was that he was deposed from the ministry of the Church that sent him forth, and became for a time the centre of an organisation which still exists, in a modified form, and bears his name; he was the bosom friend in his early days of Thomas Carlyle, and no one mourned more over his aberration than he, for he loved him to the end.  “But for Irving,” he says, “I had never known what the communion of man with man means.  His was the freest, brotherliest, bravest human soul mine ever came in contact with; I call him on the whole the best man I have ever, after trial enough, found in this world, or now hope to find.  Scotland sent him forth,” he says, “a herculean man, but our mad Babylon wore him and wasted him with all her engines, and it took her 12 years”; he died in Glasgow, aged 42, “hoary as with extreme age,” and lies buried in a crypt of the cathedral there (1792-1834).

IRVING, SIR HENRY (John Henry Brodribb), born near Glastonbury; was at first a clerk in London, appeared on the Sunderland stage in 1856, spent three years in Edinburgh, and gradually worked his way at Glasgow and Manchester, till he was invited to London ten years afterwards; his performance of Hamlet at the Lyceum in 1874 established his reputation as a tragedian; since then he has remained at the head of his profession, and both in this country and in America secured many triumphs in Macbeth, Shylock, and other Shakespearian characters, and in roles like those of Matthias in “The Bells,” “Mephistopheles in Faust,” &c.; he has contributed to the literature of Acting, and received knighthood in 1895:  b. 1838.