But, according to the ancient Irish writers, Thomond, or the Country of the Dalcassians, was originally far more extensive, for its extent is described to be from Leim Conchulainn, now Loop Head, to Slighe Dala, now Ballaghmore in the Barony of Upper Ossory a few miles to the north east of Roscrea, and from the Mountain of Echtghe, now Slieve Aughtee, on the confines of the Counties of Clare and Galway, to Sliabh Eibhlinne, now Sliebhte Eilim, or the Twelve Great Hills of Feilim, in the County of Tipperary. The country extending from the Shannon to Galway Bay and the Mountain of Echtghe originally belonged to the Province of Connaught, but Lughaidh Meann, the son of King Conell of the Swift Horses, drove the Connacians out of it and added it to Munster, to which Province it belonged until the reign of Queen Elizabeth, when it was again made a part of Connaught, but it was again added to Munster in the reign of James at the request of the Earl of Thomond.

The best guide to follow in tracing the boundaries of the principality of Thomond as it stood in the middle ages is, with some few exceptions, the Diocese of Killaloe. Thus we are told in the ancient authorities that the Kingdom of Thomond extended eastwards to Birr, to Ballaghmore in Ossory, to Sliabh Eibhlinne and Glankeen; and by turning to Beaufort’s Ecclesiastical Map, we shall find that the boundary of the Diocese of Killaloe meets that of Meath at Birr, that of Ossory at Ballaghmore near Burris in Ossory, and the Archdiocese of Cashel at Glankeen near Burrisoliagh in the County of Tipperary, and the boundary extends across the Mountain of Keeper Hill, which is the largest of the Sliabh Eibhlinne range. From this agreement we may safely conclude that the ancient boundaries of the Kingdom of Thomond are preserved on this east and south east side by those of the present Diocese of Killaloe. But its boundaries on the south side of the Shannon must be obtained from other sources, it having been too extensive a Territory to be placed in one diocese. Let us next try how we can fix its limits on the south side. In Magrath’s Wars of Thomond the extent of the country of O’Brien in the year 1194 is described as follows:-

After the death of his father, the towering warrior Donogh Cairbreach O’Brien assumed a powerful sway over the beauteous and delightful Territories of Thomond. The extent of his kingdom was from the celebrated Leim Conchullin (Loop Head) to Ath Na Boraimhe (Ballina at Killaloe) and from the borders of Birra (now Birr) to Knock Aine Cliach (Knockany near Bruff in the County of Limerick) and from Eoganacht of the smooth plain of Cashel to the north of the white rocky Burren.

We learn however, from more ancient documents preserved in the Books of Lecan and Ballymote, that Thomond or the Country of the Dal Cais was originally even more extensive than it is described (to be) in the Wars of Thomond. In the account of the division of Munster between Eogan Mor and Cormac Cas, it is expressly mentioned that the country of the latter extended southwards as far as the Mountain of Ceann Abhrat Sleibhe Caoin (at Ardpatrick to the south of Kilmallock) and that its boundary extended from a cairn on that mountain called, Carn Fearadhaigh, to Bruree on the River Maigue, and that this river formed the boundary thence to the Shannon.

According to this document all that part of the County of Limerick lying to the east of the River Maigue belonged to the Country of the Dal Cais, but though this may have been the case in the time of Eogan More and Cormac Cas, according to the will of their father Oiliol Olum, I do not believe that the Dal Cais continued to have dominion in the middle ages over all this tract lying to the south of the Shannon and to the east of the Maigue, for we learn from the Life of St. Senanus of Scattery Island that the King of the Hy-Figeinte, who was of the Eugenian line, claimed Scattery Island and all the Islands of Limerick; and the Annals of the Four Masters place the City of Limerick, which is several miles east of the Maigue, in the Territory of Hy-Figeinte.

The Life of St. Senan also places the Church of Donaghmore in the same Territory, which shews that the Hy-Figinte encroached upon the original Territory of the Dal-Cais, but we have no guide to follow in tracing the east boundary of the Country of the Hy-Figinte unless we make it coextensive with the Diocese of Limerick, and by so doing we shall perfectly agree with history and everything will square. But if we make the River Maigue the east boundary of the Hy-Figinte we shall find several passages (in history) to contradict that assumption, for Kilmallock which is east of the Maigue is stated in ancient documents published by Colgan to be situated in the Territory of Cairbre, which was a subdivision of Hy-Figinte, and Drommin Parish which is also east of the River Maigue is called in the Annals of Innisfallen and of the Four Masters, Druimin Ui Chleircin, i.e., the Hill or Ridge of O’Cleircin, who was one of the sub-chiefs of Cairbre in Hy-Figinté. Again, we find that Dermot O’Donovan, the senior of the Hy-Figinte, who, according to history, were located at Croom and Bruree, is said to have possessed all the Barony of Coshma, in the reign of King John, when he built the Castle of Croom. - See Lewis’s Topographical Dictionary.

Dr. Smith, also, in treating of the history of this family says that they came first into the County of Cork from the Barony of Coshma in the County of Limerick, where they built the famous Castle of Croom. Their locality in this Barony is also corroborated by O’Heerin, who states in his Topographical Poem that O’Donovan possessed the Territory of Cairbre Aobhdha free of tribute and had the lands along the Sluggish Maigue, and the plains down to the Shannon:-

By the lands along the Maigue, O’Heerin here evidently means the Barony of Coshma, which means along the Maigue, for the name is in Irish Cois Máighe, i.e., along the Maigue.

It may be urged that “along the Maigue” may mean along that river on the west side, but the situation of the present Barony of Coshma, the greater part of which lies on the east side of the Maigue, is the best evidence of what the ancient Irish meant by the name, and must now be received to prove what O’Heerin meant by “along the Sluggish Maigue.”

From the above reference to the Territory of Hy-Figinte and the families located in it, we may conclude with some safety that it was co-extensive during the middle ages with the present Diocese of Limerick, excepting only that small part of it lying on the north side of the Shannon, and that all the Diocese of Emly was included in the Country of the Dal-Cais.

Having premised so much, I shall venture to define the limits of the Country of the Dal Cais, commonly called Thomond, as follows:-

The principality of Thomond, generally called the Country of the Dal-Cais, comprised the entire of the present Co. of Clare, the Parishes of Iniscaltra and Clonrush in the County of Galway, the entire of Ely O’Carroll, the Baronies of Ikerrin, Upper and Lower Ormond, Owney and Arra, and somewhat more than the western half of the Barony of Clanwilliam in the County of Tipperary; the Baronies of Owenybeg, Coonagh and Clanwilliam, and the eastern halves of the Baronies of Small County and Coshlea in the County of Limerick.

Having thus defined, according to the best historical evidences, the extent and boundaries of Thomond, I shall at once proceed to point out the number and extent of the Territories comprised in that part of it included in the present County of Clare, which was considered in the reign of Queen Elizabeth to be the Country properly called Thomond or North Munster. I shall begin at the north with Burren and Corcomroe and proceed in a south western direction so as to take in all the country which had been occupied by the families of the Rudrician race before they were dispossessed by the O’Briens and other families of the race of Cormac Cas.