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 and from opposite sides of the principality. Eventually Sedgwick founded the Cambrian system for the oldest group of fossiliferous strata, and Murchison the Silurian system for the great group immediately below the Old Red Sandstone. Their systems were found to overlap—Sedgwick's Upper Cambrian and Murchison's Lower Silurian being practically equivalent. Hence arose a painful controversy that has only of late years been terminated by the adoption of Professor C. Lapworth's term Ordovician in place of the Upper Cambrian of Sedgwick and the Lower Silurian of Murchison.

Sedgwick was ever actively interested in the work of his university. His famous Discourse on the Studies of the University of Cambridge, delivered in 1832, was published in expanded form in 1833; it reached a fifth edition in 1850. The studies were reviewed under the headings of (1) The laws of nature, (2) Ancient literature and language, and (3) Ethics and metaphysics; and the volume had so grown that it ultimately consisted of 442 pages of preface, or preliminary dissertation on the history of creation, with arguments against the transmutation of species, and an essay on the evidences of Christianity; the discourse occupied 94 pages; and there was an appendix of notes, &c., that filled 228 pages.

In 1833 Sedgwick was president of the British Association at the first Cambridge meeting, and in 1834 he was appointed a canon of Norwich. In 1836 with Murchison he made a special study of the Culm-measures of Devonshire, which until that time had been grouped with the greywacke, and together they demonstrated that the main mass of the strata belonged to the age of the true Coal Measures. Continuing their researches into the bordering strata they were able to show in 1839, from the determinations of William Lonsdale, that the fossils of the South Devon limestones and those of Ilfracombe and other parts of North Devon were of an intermediate type between those of the Silurian and Carboniferous systems. They therefore introduced the term Devonian for the great group of slates, grits and limestones, now known under that name in West Somerset, Devon and Cornwall. These results were published in the great memoir by Sedgwick and Murchison, “On the Physical Structure of Devonshire” (Trans. Geol. Soc., 1839). Of later published works it will be sufficient to mention A Synopsis of the Classification of the British Palaeozoic Rocks (1855), which contained a systematic description of the fossils by F. McCoy. Also the preface by Sedgwick to A Catalogue of the collection of Cambrian and Silurian Fossils contained in the Geological Museum of the University of Cambridge, by J. W. Salter (1873).

The Wollaston Medal of the Geological Society was awarded to Sedgwick in 1851, and the Copley Medal of the Royal Society in 1863. He continued to lecture until 1872, when ill-health rendered necessary the appointment of a deputy (Professor J. Morris). He died at Cambridge on the 27th of January 1873.

SEDGWICK, JOHN (1813–1864), American general, was born at Cornwall, Connecticut, on the 13th of September 1813, and graduated at West Point in 1837. Amongst his classmates were Joseph Hooker, Braxton Bragg and J. A. Early. He saw active service against the Seminoles in Florida, and took part as an artillery officer in the Mexican War, winning the brevets of captain and major for his conduct at Contreras-Churubusco and Chapultepec. In command first of a brigade and later of a. division in the Army of the Potomac, he took part in the Seven Days' and Maryland campaigns. At the battle of Antietam he was twice wounded, but remained on the field. Soon afterwards he was given command of the VI. corps, in which position he took an important part in the battle of Chancellorsville, capturing the famous lines of Fredericksburg and fighting the severe battle of Bank's Ford. The VI. corps bore a share in the battle of Gettysburg, having made a fine forced march to the field. Sedgwick had been offered the chief command of the army upon Hooker's resignation; but he declined, and retained his command of the VI. corps during the Virginian campaign of the autumn of 1863, being on several occasions placed by Meade in charge of a wing of the army. He was also given the command of the whole army in Meade's absence. At the action of Rappahannock station Sedgwick by a brilliant night attack destroyed two brigades of Early's division (November 7th). When Grant became commanding-general and the Army of the Potomac was reorganized in three corps, the VI. was one of these, and Sedgwick thus led his old corps, now greatly augmented, at the battle of the Wilderness. At the opening of the battle of Spottsylvania Court House, Sedgwick was killed (9th of May 1864) by a shot from a Confederate skirmisher. A monument to his memory, cast from the guns taken in action by the VI. corps, was erected at West Point in 1868.

SEDILIA (the plural of Lat. sedile, seat), in ecclesiastical architecture, the term given to the seats on the south side of the chancel near the altar for the use of the officiating priests. They are generally three in number, for the priest, deacon and sub-deacon. The custom of recessing them in the thickness of the wall began about the end of the 12th century; some early examples consist only of stone benches, and there is one instance of a single seat or arm-chair in stone at Lenham in Kent, thought by some to be a confessional. The niches or recesses in which they are sunk are often richly decorated with canopies and subdivided with moulded shafts, pinnacles and tabernacle work; the seats are sometimes at different levels, the eastern being always the highest, and sometimes an additional niche is provided in which the piscina is placed.

 SEDITION (Lat. se or sed, apart, and ire, to go, a going apart, dissension), in law, an attempt to disturb the tranquillity of the state. In Roman law sedition was considered as majestas or treason. In English law it is a very elastic term, including offences ranging from libel to treason (q.v.). It is rarely used except in its adjectival form, e.g. seditious libel, seditious meeting or seditious conspiracy. “As to sedition itself,” says Mr Justice Stephen, “I do not think that any such offence is known to English law ” (Hist. Crim. Law, vol. ii. chap. xxiv.). The principal enactments now in force dealing with seditious offences were all passed during the last twenty-five years of the reign of George III. They are the Unlawful Oaths Act 1797, prohibiting the administering or taking of unlawful oaths (see ) or the belonging to an unlawful confederacy; the Unlawful Drilling Act 1819–1820 prohibited unlawful drilling and military exercises; and the acts for the suppression of corresponding societies, the Unlawful Societies Act 1799 and the Seditious Meetings Act 1817. No proceedings can be instituted under these last two acts without the authority of the law officers of the crown (Corresponding Societies, &c., Act, 1846). Under the head of statutes aimed at seditious offences may also be classed statutes of Richard II. (1378, 1388) against scandalum magnatum or slander of great men, such as peers, judges or great officers of state, whereby discord may arise within the realm, and a statute of Charles II. (1661) against tumultuous petitioning (see ). There has been no prosecution for many years for seditious words as distinguished from seditious libel, but such words have been admitted as evidence in proceedings for seditious (q.v.), as in the prosecution of O'Connell in 1844 and of C. S. Parnell and others in 1880 (see Reg. v. Parnell, Cox's Criminal Cases, vol. xiv. 508). By the Prison Act 1877, any prisoner under sentence for sedition or seditious libel is to be treated as a misdemeanant of the first division.