Ireland as contained in the Government of Ireland Act 1920. It states that "Northern Ireland shall consist of the parliamentary counties of Antrim, Armagh, Down, Fermanagh, Londonderry and Tyrone, and the parliamentary boroughs of Belfast and Londonderry, and Southern Ireland shall consist of so much of Ireland as is not comprised within the said parliamentary counties and boroughs." The border has some distinctive features. Firstly, how irregular it is: the border is about four times the straight-line distance between Lough Foyle and Carlingford Lough. Second, County Donegal is only connected to the rest of the Republic of Ireland by a territorial isthmus wide, making it more convenient for some journeys from Donegal to other parts of the Republic of Ireland to pass through Northern Ireland. Third, for only two relatively short sections of the border does it align with the provincial boundary of nine county Ulster between Fermanagh-Leitrim and Armagh-Louth. And lastly, as the border skirts Tyrone to the west and again to the south east, it encompasses Co. Fermanagh on three sides.