The stronghold of the tribe was the _Dun_ or fort, which the _Ri_ alone had a right to occupy, and of which each king was bound to have at least three. The description given of it is as follows:—‘Seven score feet are the dimensions of the Dun every way; seven feet the thickness of the mound at top; twelve feet at bottom. Then only is he king, when he is encircled by the moat of servitude. Twelve feet is the breadth of its mouth and of its bottom, and its length is the same as the Dun. Thirty feet is its length on the outside.’[168] The average number of fighting men which a tribe turned out on ordinary occasions appears to have been 700.[169] The possessions of the Church within the territory of the tribe varied in extent from half a _Ballyboe_ or ploughgate, till in some cases the Dun itself and the possessions of the king or chief were granted to found a monastery, and in those cases where the monastery was said to have consisted of 3000 monks, the tribe itself appears to have merged in the Church. There came to be a lay and a clerical _progenies_, and the head of the tribe appears to have been chosen alternately from the tribe of the land and the tribe of the patron saint.[170] The free and bond _Ceile_ then became free and bond _Manachs_, their position being substantially the same. [Sidenote: The _Mortuath_.] Such being the aspect in which the tribe is presented to us in the ancient laws of Ireland, it must not be assumed that these tribes, thus possessing a complete organisation in themselves, were at this period independent of each other. From even a much earlier period they seem to have been united in a constitutional framework, by which they formed a kind of federal nation. Several of these _Tuaths_ were grouped together to form a still larger tribe, termed a _Mortuath_ or great tribe, over whom one of the kings presided as _Ri Mortuath_. The normal number forming a _Mortuath_ is in one place stated as three, and in another seven. [Sidenote: The _Cuicidh_ or province.] Then several of these _Mortuath_ formed a province, called in Irish _Cuicidh_, or a fifth. The name is interpreted as implying that the _Mortuath_ thus united were five in number, but the usual explanation is more probable, that as there were five provinces in Ireland—Meath, Leinster, Munster, Connaught, and Ulster—it means that each was the fifth part of Ireland. Over each province was the _Ri Cuicidh_, or provincial king, and then over the whole was the _Ardri_, or sovereign of all Ireland. [Sidenote: The law of Tanistry.]