e 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.

SIERRA NEVADA, 1, a mountain range in South Spain, 60 m. in length;
lies for the most part in Granada, crossing the province E. and W. in
bold, rugged lines, and clad on its higher parts with perpetual snow,
whence the name; Mulhacen (11,660 ft.) is the highest peak. 2, A mountain
system in California, stretching NW. and SE. 450 m., and forming the
eastern buttress of the Great Central Valley; highest peak Mount Whitney
(14,886 ft.). 3, A lofty mountain group in Colombia, South America,
stretching NE. almost to the borders of Venezuela.

SIEYES, ABBE, a c