The National Gazetteer of Great Britain and Ireland - 1868
"GERRANS, (or Gerrance), a parish in the hundred of West Powder, county Cornwall, 7 miles S.E. of Truro, and 4 N. of St. Mawe's. It is situated at the upper extremity of St. Mawe's Harbour, being bounded on the E. by the English Channel. It formerly formed part of the demesne of the bishops of Exeter. It includes the hamlets of Porthskaths and Trewithan. The land is rich, and the soil chiefly arable. Slate occurs in some parts. The living is a rectory in the diocese of Exeter, value £258, in the patronage of the bishop. The church is situated on an eminence commanding a fine prospect. It is dedicated to St. Guron, and contains a handsome monument to the Hobbs family. The Independents and Wesleyans have chapels. There is a parochial school. On the estate of Trewithan are remains of an ancient fortress called Dun-gerein, reported by tradition- to have, been the castle of King Gerennius.