PORTLAND, ISLE OF, a peninsula and parish of Eng-
land, in the county of Dorset, is joined to the land by
Chesil Bank, which is a narrow ridge of clay covered
with shingles, about 10 miles in length. The isle itself is
about 4 miles in length by 2 in breadth; and it terminates
in a rocky promontory called the Bill of Portland, on which
stand two lighthouses,—the one 130, and the other 197
feet above the sea, N. Lat. 50. 3., W. Long. 2. 26. It
consists of oolitic limestone, and slopes gradually from a
height of 490 feet to within 30 feet of the sea. Portland
Isle is approached from the land by a wooden bridge 600
feet long. It contains the castle of Portland, built by
Henry VIII. in 1520; the Bow and Arrow Castle, a rudely-
built tower, said to have been erected by William Rufus;
a convict prison, erected in 1849; and several small villages.
There are also here extensive quarries of Portland stone,
with which many of the public edifices in the kingdom have
been built. A harbour of refuge is in process of being
constructed at Portland by means of a breakwater from the
north end of the isle, partly enclosing Portland road. It
is intended to be 2500 yards long, and to extend to a dis-
tance of 1½ miles from Weymouth pier, thus sheltering
from the S.E. an area of 2107 acres at low-water; while
Chesil Bank forms a natural breakwater on the S.W. The
work was begun August 11, 1847, and up to March 31, 1857,
it had been extended to a length of 5145 feet by the deposi-
tion of 2,667,905 tons of Portland stone. The sum expended,
from the beginning of the works up to March 31, 1857, was
L.627,585. Pop. of the parish of Portland (1851), 5195.