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 804 SEXTUS EMPIRICUS SEYMOUR have been made. To the navigator the sex- tant is invaluable ; and in the special work of hydrography along a coast line, where the posi- tion of the boat or vessel is generally deter- mine^ by observing from the boat, the sextant is the only available instrument of precision in use. And yet in its ordinary form it has cer- tain deficiencies which prevent its universality of application. This fails to measure the an- gles between 140 and 180, and the hydrogra- phers of all countries have studied to remedy this defect, with varied success. M. Daussy, a very skilful French hydrographer, and Messrs. Piston and Martius, instrument makers of Ber- lin, have in different ways modified the form of the sextant so as to overcome this difficulty ; but their instruments are embarrassing in their manipulation, especially when the objects are indistinct or the observation must be made from a boat continually disturbed by the action of the waves. Mr. T. J. Lowry of the United States coast survey has succeeded in removing this imperfection in the sextant, and has also made other improvements by which many other difficulties are overcome. The improved instruments are handled with the same facil- ity as the old soxtant, and are equally adapted to rough usage in a boat. By means of some additional glasses and certain improvements in the graduated arcs and verniers, the following objects are accomplished : any angle from to 180 can be measured without inverting the instrument and while reflecting but one object; two angles, one to the right and the other to the left of an object, either angle be- ing any number of degrees from to 120, can be measured at the same instant. By certain additions which are easily made to the ordi- nary sextant, Mr. Lowry makes the instrument capable of measuring two angles, one to the right and the other to the left of the central object, in quick succession, without previously estimating their relative magnitudes, or invert- ing the instrument or lengthening its arc. Lastly, by a modification of M. Daussy's im- provement, Mr. Lowry makes the ordinary sextant capable of measuring an angle and giving an inter-range at the same instant, and also of fulfilling many other conditions which M. Daussy's will not. SEXTUS EMPIRICl'S, a Greek philosopher, a native of Mytilene, in the first half of the 8d century A. D. His medical writings are lost ; but his Pyrrhonia Hypotypoaet, in three books, an exposition of the doctrines of the skeptics, and a treatise against the mathematicians, in 11 books, in which he attacks all the sciences, both physical and metaphysical, remain. An edition of both, with a Latin translation, was prepared by J. A. Fabricius in 1718. Bekker published an amended edition (Berlin, 1842). SEYCHELLES. See MAUBITIUS, vol. xi., p. 293. SF.MH.IT/, or Stldlitz, Friedrirh Wilhelm TOD, a Prussian soldier, born at Ealkar, near Cleves, Feb. 3, 1721, died near Namslau, Silesia, Nov. 7, 1773. He excelled in horsemanship from his boyhood. After serving as a page of the margrave of Schwedt, he entered the Prussian army in 1739, and won the rank of major at Hohenfriedberg, June 4, 1745, and that of ma- jor general at the battle of Kolin, June 18, 1757. In the same year he was put in com- mand of the cavalry, and distinguished him- self at Rossbach, Nov. 5, at Zorndorf and Iloch- kirch in 1758, and especially at Kunersdorf, Aug. 12, 1759, where he was seriously wound- ed, and at Freiberg, Saxony, Oct. 29, 1762. He was then made inspector of the cavalry in Silesia, and in 1767 general of cavalry, to which branch of arms he had imparted a wonderful efficiency. See Leben dea Generals von Seyd- litz, by Varnhagen von Ense (Berlin, 1834), and Der General Friedrich Don Seydlitz, by Count Friedrich Wilhelm von JBismark (1837). SEYFFARTH, Gnstav, a German archaeologist, born at Uebigau, Saxony, July 13, 1796. He studied at Leipsic, where in 1825 he became extraordinary professor of archreology. In 1824 he published De Sonis Litterarum Grce- carum (Leipsic). He edited and continued Spohn's De Lingua et Litteris Veterum JEgyp- tiorum (2 vols., 1825-'31), and published Ru- dimenta Hieroglyph ices (1826). His Grund- siitze der Mythologie (1843) and Untersuch- unyen fiber das Geburttyahr Christi (1846) involved him in bitter controversies. His pe- culiar theory of hieroglyphics he maintained against Champollion, and he now (1875) claims that the Champollionists have passed off his system as their own. In 1855 he emigrated to the United States, and was for six years professor in the Lutheran seminary of St. Louis. In 1857 he published at New York a " Summary of recent Discoveries in Biblical Chronology, Universal History, and Egyptian Archrcology," both in English and German, and in 1860 a pamphlet in German refuting the chiliasts. He has for some time been en- gaged on a work entitled " The actual Histori- cal Chronology of the Romans, Greeks, Baby- lonians," &c. His last publication is " Clavis ^Egyptiaca, a Collection of all Bilingual and some other Hieroglyphic Inscriptions, trans- lated and explained." SEYMOUR. I. Edward, duke of Somerset, an English statesman, known as the protector Somerset, born about 1500, beheaded on Tower hill, London, Jan. 22, 1552. He was the eldest son of Sir John Seymour, and was educated at Oxford. After the marriage of his sister, Jane Seymour, with Henry VIII., he was created Viscount Beauchamp and earl of Hertford, and gradually became one of the most powerful noblemen about the person of the king, his pres- tige being strengthened by military successes in Scotland and France in 1544. He was one of the 16 persons appointed by Henry VIII. in his will to be his executors and the governors of the young king, Edward VI. ; and in Feb- ruary, 1547, he was created duke of Somerset and earl marshal of England. On March 12