Griffiths Valuation has 3 William Colquhoun households listed in Ireland. One is in Curraghmulkin, in the parish of Longfield East, in Tyrone. The second is in Edencarnin South, the third nearby in Killydesert, both in the parish of Kilmacrenan, in Co Donegal. These two are close together and could well be owned by the same person, or if not it’s likely to be a relative.
Edencarnin South/Killydesert are a little to the west of the N56 from Letterkenny to Kilmacrenan. In 1858, the main farm is on Edencarnin where William has a house, offices (outbuildings) and 57 acres which he shares with Alex Colquhoun, who also has a separate house and offices. The property in Killydesert is a caretakers house, offices and 5 acres.
http://www.askaboutireland.ie/griffith-valuation/index.xmlIn Curraghmulkin, the William there, in 1859, had a house, offices and 8 acres plus a share of a mountain for grazing etc with some others. Curraghmulkin is beside the Holme Rd, which leads off the B84 Dooish Rd, which is about 10 miles west of Oamgh.
There were no Colquhoun households in Curraghmuklkin by the 1901 census:
www.census.nationalarchives.ie/pages/1901/Tyrone/Drumquin/Cu...No Colquhouns in Killydesert in 1901:
http://www.census.nationalarchives.ie/pages/1901/Donegal/Ede...But there was one family in Edencarnan South:
http://www.census.nationalarchives.ie/pages/1901/Donegal/Ede...Note that the spelling of the surname will vary in Ireland. No-one bothered too much about that in those days. Can’t see any will listed for either family on the PRONI website.
Your next step would be to search local church records. They were probably all Presbyterian. You can see what records exist on the PRONI website:
http://www.proni.gov.uk/index/research_and_records_held/cata...