528 M I T M I T of wrought-iron ware and of white-lead being the most im portant. The river Aa brings Mitau in connexion with the trade of Riga, small vessels carrying goods to the amount of about 150,000 a year. Mitau is supposed to have been founded in 1266 by the grand master Conrad Mandern. It has often changed its rulers. In 1345, when it was plundered by Lithuanians, it was already an important town. In 1561 it became the residence of the dukes of Ctnirland. During the 17th century it was thrice taken by the Swedes. Russia annexed it with Courland in 1795. At the be ginning of this century it was the residence of the count of Provence (afterwards Louis XVIII.). In 1812 it was taken by Napoleon I. MITCHEL, ORMSBY M KNIGHT (1810-1862), American general and writer on astronomy, was born in Union county, Kentucky, August 28, 1810. He began life as a clerk, but, obtaining an appointment to a cadetship at West Point in 1825, he graduated there in 1829, and became assistant professor of mathematics in 1831. Subsequently he was called to the bar, but forsook law to become professor of mathematics and natural philosophy at Cincinnati college. There he established an observatory, of which he became director. From 1859 to 1861 he was director of the Dudley observatory at Albany. He took part in the war as brigadier-general of volunteers, and for his skill and rapidity in seizing certain important strategic points was on April 11, 1862, made major-general. He died of yellow fever at Beaufort, South Carolina, October 30, 1862. Besides making important improvements on several astrono mical instruments, Mitchel was the author of several works on astronomy, the principal of which are The Planetary and Stellar Worlds (1848) and The Orbs of Heaven (1851). See Memoir by Headley (1865). MITCHELL, SIR THOMAS LIVINGSTONE (1792-1855), Australian explorer, was a son of Mitchell of Craigend, Stirlingshire, where he was born, June 16, 1792. From 1808 to the end of the Peninsular War he served in Wellington s army, and for his services received the medal and five clasps, and was raised to the rank of major. He was appointed to survey the battlefields of the Peninsula, and his map of the Lower Pyrenees is still admired. In 1827 he was appointed deputy surveyor-general, and after wards surveyor-general, of New South Wales. He devoted himself to the exploration of Australia, making four expeditions for that purpose between 1831 and 1846. During these expeditions he discovered the Peel, the Namoi, the Gwyder, and other rivers, traced the course of the Darling and Glenelg, and was the first to pene trate into that portion of the country which he named Australia Felix. His last expedition was mainly devoted to the discovery of a route between Sydney and the Gulf of Carpentaria, and during the journey he explored the Fitzroy Downs, and discovered the Balonne, Victoria, Warrego, and other streams. In 1838, while in England, Mitchell published the narrative of his first three journeys, Three Expeditions into the Interior of East Aitstralia (2 vols.). In 1839 he was knighted and made a D.C.L. of Oxford. During this visit he took with him some of the first specimens of gold and the first diamond found in the country. In 1848 the narrative of his second expedition was published in London, Journal of an Expedition into the Interior of Tropical Australia. In 1851 he was sent to report on the Bathurst gold-fields, and in 1853 he again visited England and patented his boomerang propeller for steamers. He died at his residence at Darling Point, Sydney, October 5, 1855. Besides the above works, Mitchell wrote a book on Geographical and Military Surveying (1827), an Australian Geography, and a translation of the Las tad of Camoens. MITE. Mites (Acarina) are minute creatures which form a large division of the Arachnida, distinguished by the absence of any constriction between the cephalothorax and abdomen. Linnaeus included all in the single genus Acarus. They are now divided into several families (mostly containing numerous genera), viz., Trombidiidse, (harvest mites), usually scarlet specks seen running on stones, grass, &c., in hot weather ; Tetra- nychi, which, although not bright red, are the red spider of our green-houses, and are distinguished by feet with knobbed hairs ; fldellidse, long-snouted mites with an- tenniform palpi ; Cheyletidx (fig. 1), the so-called book mites, ferocious, predatory little beings, quite uncon nected with books ; Hydrachnidx, freshwater mites with swimming legs, mostly beautiful creatures of brilliant colours; Limnocaridx, crawling freshwater or mud mites; Halicaridge, chiefly marine ; Gamasidx, hard-skinned brown mites often parasitic on insects, and best known by the females, and young of both sexes, found on the common dung beetle (Geotrupes stercorarius) ; Ixodidse, the true ticks, not to be confounded with the sheep-tick, &.C., which FIG. l. Cheylctusjlaleilifcr. FIG. 2. Leiosoma palmicinclum ; nymph. are wingless flies ; Oribatidx, beetle mites, so called from their resemblance to minute beetles (these are never parasitic; they undergo transformations almost as strange as those of insects, many of the immature forms being quaint and beautiful, see fig. 2); Myobiadse, bizarre para sites of the mouse, &c., with peculiar holding claws ; Tyroglyphidse, the cheese mites; Analgidx, found on the feathers of birds ; Sarcoptidae, the itch mites ; Arctisco>iidr, the water bears ; Demodicidee, found in the sebaceous follicles of the human nose, fec. ; and Phytoptidse, the gall mites, which attack the leaves of plants, making tiny gall- like excrescences. The sexes are distinct individuals; the reproduction is oviparous; the larva is almost always hexapod, though the later stages have eight legs ; that answering to the pupa of insects is active, and is called the nymph. The breathing in the first-named eleven families is tracheal, the position of the stigmata varying greatly ; in the last-named six families it is by the general body surface. No heart or circulation of the blood is known to exist; the alimentary canal is usually somewhat on the insect type, but with csecal prolongations to the stomach, the reproductive organs often more on the crustacean type. There is generally a single very large nerve-ganglion above the oesophagus, sending nerve-branches
to the various parts. The legs have ordinarily five to