Henry II. to Prince John who, in 1204, made Hugh Nevill
governor of the castle. In 1216 William Ferrers, earl of Derby, took it
from the rebellious barons, and was made governor by Henry III., who in
1223 granted a charter for a weekly market at the town. In 1328 the
castle was given to John of Gaunt on his marriage with Blanche of
Lancaster, and thus became parcel of the duchy of Lancaster. The castle
has often been used as a prison, and from its position was almost
impregnable.

CASTLETOWN (Manx, _Bully Cashtel_), a town of the Isle of Man, 10 m.
S.W. of Douglas, by the Isle of Man railway. Pop. (1901) 1975. It is
picturesquely situated on both sides of a small harbour formed by the
outflow of the Silver Burn into Castletown Bay. It was the legal capital
of the island until 1862. In the centre of the town stands Castle
Rushen, which is said to owe its foundation to the Danish chief,
Guthred, in 947-960, though the existing building, which is remarkably
well preserved, probably dates from the 14th century. Until the 18th
century it was the residence of the lords of Man, and until 1891 served
as a prison. The massive keep is square, and is surrounded by an outer
wall, with towers and a moat. The council chamber and court-house were
built in 1644. In the neighbourhood of the castle is the old House of
Keys, where the members of the Manx parliament held their sessions until
the removal of the seat of government to Douglas. A lofty Doric column
commemorates Cornelius Smelt, lieutenant-governor of the island (d.
1832), near which there is a remarkable sun-dial with thirteen faces,
dating from 1720. King William's College, situated a mile to the
north-east of the town, was opened in 1833; but a complete restoration
was rendered necessary by fire in 1844, and it was subsequently
enlarged. It is the chief educational establishment in the island. At
Hango Hill near the town William Christian, receiver-general, who had
surrendered the castle, and with it the island, to the parliamentary
forces in 1651, was executed in 1663 at the instance of the countess of
Derby, who had undertaken to defend it for the king. A small shipping
trade is maintained.

CASTOR and POLLUX (Gr. [Greek: Poludeukes]), in Greek and Roman
mythology, the twin sons of Leda, and brothers of Helen and
Clytaemnestra. They were also known under the name of Dioscuri ([Greek:
Dioskoroi], later [Greek: Dioskouroi], children of Zeus), for, according
to