CASTLEBUOY, or ST. JOHNSTOWN, an extra-parochial liberty, in the barony of ARDES, county of DOWN, and province of ULSTER, 3 miles (N. E.) from Portaferry; containing 744 inhabitants. This place is situated on Cloghy bay, and, according to the Ordnance survey, comprises 1358? statute acres. A commandery or preceptory of St. John the Baptist of Jerusalem, dependent on the priory of Kilmainham, was founded here by Hugh de Lacy, in 1189, which continued till the commencement of the fifteenth century; the building is now in ruins, and the family of Echlin possesses several townlands in freehold which have always enjoyed exemption from tithe and church cess, and also a manor which belonged to the commandery, the court of which is now held once in three weeks. The manor is called Cloghy, and the court has jurisdiction over the liberty of Castlebuoy, the parishes of Slanes and Ballytrustin, and part of Witter, and any sum not exceeding #5 is recoverable in it, either by attachment or civil bill process. The lofty tower of the castle and ruins of the church are situated in one of the most secluded and fertile vales in the Ardes. On a chain of rock in the channel, three miles east from the shore, is the South Rock or Kilwarlin light-house.There is a private school, in which are about 70 boys and 60 girls.