sentences:  It was therefore about then that possession of St Mary's Isle was obtained by Lord Selkirk, The 4th Earl, who was seen to gradually add to the St Mary's Isle Estate.In 1786 he transferred management of his estates to his then eldest son, Basil William, The Lord Daer, who conducted his affairs with great success.Dunbar, 4th Earl of Selkirk, died in 1799, and was succeeded by his youngest son Thomas, his other sons having predeceased him, as the 5th Earl of Selkirk.