SIEMENS, WERNER VON, a celebrated German electrician and inventor, born at Lenthe, Hanover; served in the Prussian artillery, and rendered valuable services in developing the telegraphic system of Prussia; patented a process for electro-plating in gold and silver, and was the first to employ electricity in exploding submarine mines; retired from the army in 1849, and along with Halske established a business in Berlin for telegraphic and electrical apparatus, which has become notable throughout the world, having branches in several cities; made many contributions to electrical science; was ennobled in 1888 (1816-1892).

SIEMENS, SIR WILLIAM (Karl William), younger brother of the preceding, born at Lenthe, Hanover; like his brother took to science, and in 1844 settled in England, naturalising in 1859; was manager of the English branch of the Siemens Brothers firm, and did much to develop electric lighting and traction (Portrush Electric Tramway); his inventive genius was productive of a heat-economising furnace, a water-meter, pyrometer, bathometer, &c.; took an active part in various scientific societies; was President of the British Association (1882), and received a knighthood in 1883 (1823-1883).

SIENNA or SIENA (28), an interesting old Italian city of much importance during the Middle Ages, in Central Italy, 60 m.  S. of Florence, is still surrounded by its ancient wall, and contains several fine Gothic structures, notably its cathedral (13th century) and municipal palace; has a university and institute of fine arts; silk and cloth weaving, and a wine and oil trade are the chief industries.

SIERRA, the name given to a range of mountains with a saw-like ridge.

SIERRA LEONE (75), a British maritime colony since 1787, on the W. coast of Africa, having a foreshore of 180 m. between Rivieres du Sud (N.) and Liberia (S.); includes the peninsula of Sierra Leone proper with its densely-wooded Sugar-Loaf Mountain, and a number of coast islands, and stretches back to a highland eastern frontier ill defined; the climate is hot, humid, and unhealthy; has been called “The White Man’s Grave”; is fertile, but not well exploited by the indolent negro population, half of whom are descendants from freed slaves; ground-nuts, kola-nuts, ginger, hides, palm-oil, &c., are the principal exports.  FREETOWN (q. v.) is the capital.  The executive power is exercised by a governor and council of five.

SIERRA MADRE, the main cordillera system of Mexico, extending in a northerly direction to Arizona, and forming the western buttress of a fertile plateau stretching eastwards; to the W. the States of Sinaloa and Sonora slope downwards to the sea.

SIERRA MORENA, a mountain chain in South Spain, forming the watershed between the valleys of the Gaudiana (N.) and Guadalquivir (S.); has valuable deposits of lead, silver, quicksilver, and other metals.