‘Castle of Doe – or MacSwine’s Castle, is situated on Cannon-point, a peninsula but little broader than its extent, on the bay of Ards, to the demesne of which it appears in various handsome views. It was built by a lady of the name of Quin, who afterwards married one of the Mc’Swine family, a couple of years before the reign of Queen Elizabeth; it was since then fortified with a strong bawn by the grandfather of the present Mr. Mc’Swine of Dunfanaghy; it was only of small extent, but very strong, and surrounded by a deep fosse, which admitted the sea-water on the landside.’
From Statistical Survey of the County of Donegal by Dr James McParlan (1802)

‘The MacSwines held Doe Castle (Dhuv or Black Castle) for ages. It is a lofty round tower, surrounded by high walls, on the northern coast of Donegal, at the entrance of a small bay or estuary. It is in perfect preservation, and is inhabited to the present moment. It contains several good rooms, especially a banqueting-hall, and the view from the top is grand and extensive. Up to the reign of Elizabeth, it was held by the MacSwines. After the rebellion of Sir Cahir [O’Doherty, killed at the Battle of Kilmacrennan, 1608], it came into the hands of captain Harte, or Culmore, and is at the present date the property of lieutenant Harte, R.N., the lineal descendant of the governor of Culmore.
The Hartes retain the property they got to the great extent at Sir Cahir’s death. The present head of the family, lieutenant Harte, resides at Kilderry, near Culmore, and is considered to be worth from £1,500 to £2,000 per annum. His grandfather, General Harte, of the Indian service, lived at Doe Castle and, of course, extraordinary stories of the nabob are circulated freely in the neighbourhood. He was at the taking of Seringapatam, and, if we can credit rumour, made a very considerable “loot” thereat.’
From The Fate and Fortune of Hugh O’Neill, Earl of Tyrone and Rory O’Donel, Earl of Tyrconnel, by the Rev. C.P. Meehan (1868)

‘The Hartes of Culmore and Kilderry were the owners of Doe Castle and the landed property attached up to the year 1866 when it was purchased by Mr. Stewart of Ards. General Harte, of the Indian Service, who was present at the battle of Seringapatam and at the capture of Tipoo Sahib, lived at Doe Castle for many years in true Oriental magnificence. He met with an accident by falling down the steep staircase leading to the tower, from which death ensued afterwards. Captain Harte, his son, who succeeded him, was famous for his hospitality and very popular with the people. Tippp Sahib’s body-servant, a Hindoo, was made prisoner by the General, brought to Ireland and died at Doe Castle. He slept at night at the General’s bedroom door, dressed in oriental costume, and fully armed. The Hindoo’s health started to decline after his master’s death, to whom he was devotedly attached, and in a few years he died broken-hearted. The cannon captured at Seringapatam are yet to be seen on a green lawn sloping downwards to the sea from the outward walls of the castle…’
From Scenery and Antiquities of North-West Donegal by William Harkin (1893)