a town of Wales, in the county of Glamorgan and hundred of Newcastle, 187 miles from London. It stands at the foot of a high mountain, where once stood a Cistercian abbey, supposed to have been erected in 1147 by William, duke of Gloucester. The ruins still exist, but one part is entire, a circular apartment, twelve feet in diameter, with twelve pointed windows, and the roof resting on a single pillar in the centre. The population of Margam amounted in 1801 to 1809, in 1811 to 1803, in 1821 to 2047, and in 1831 to 2902.