| Amolngaid | reigned | 20 | years |
| Ailill Molt | ” | 11 | ” |
| Duach, son of Brian | ” | 20 | ” |
| Eogan | ” | 37 | ” |
| Ailill | ” | 5 | ” |
| Eogan Srem | ” | 27 | ” |
| Duach, son of Fergus | ” | 7 | ” |
| Eochaid | ” | 1 | ” |
| Aed | ” | 25 | ” |
| Total | 153 | ” |
Reckoning back 153 years from A.D. 577, we reach A.D. 424. The date of Dathi’s death was A.D. 428, but if we take into account the conditions of such a calculation, where incomplete years may be set down as full years, the divergence might be consistent with the conclusion that the list was constructed on the initial assumption that Amolngaid succeeded Dathi in 428—which implies that Dathi was king of Connaught (but see below).
We can now see how the chronology was constructed in O’Duinn’s source. It will be simplest, for the purpose of criticism, to tabulate the dates (approximately) implied by that construction:—
| Amolngaid | ceased to reign | 444 |
| Ailill I. | ” | 455 |
| Duach I. | ” | 475 |
| Eogan I. | ” | 512 |
| Ailill II. | ” | 517 |
| Eogan II. | ” | 544 |
| Duach II. | ” | 551 |
| Eochaid | ” | 552 |
| Aed | ” | 577 |
These dates are entirely at variance with the chronology of the Annals. We are entitled to criticise them on the assumption that the dates of the Annals for the battles of Segais, Sligech, and Cuil Conaire are approximately correct. O’Duinn’s figures would place Segais c. 475 instead of 502 (or 500), Sligech c. 512 instead of 543 (or 547), Cuil Conaire c. 517 instead of 550. But if we omit from his list Eogan II. and Duach II., and then reckon back from 577, we get approximately dates assigned in the Annals to the second and third of these three battles, namely, 551 for Cuil Conaire, 546 for Sligech; while the contradiction between the duration of Eogan Bel’s reign and the date of Segais is the same here as in the other sources. If Segais was fought in 502 and Sligech in 546/7, and Eogan Bel reigned thirty-seven years, then seven or eight years are left unaccounted for, and the reign of the second Duach serves to fill this interval. But there is no room for Eogan Srem between the battle of Segais and the death of Aed.
Again, if we take Duach I.’s death at Segais in 502 as a fixed point, and reckon backward with O’Duinn’s figures, we find 482 for the accession of Duach I., 471 for the accession of Ailill Molt, and 451 for the accession of Amolngaid. If Amolngaid followed Dathi in 428, this would imply an error of about twenty-four years.
We have now the clue to the construction of O’Duinn’s list. A period of c. 153 years from the accession of Amolngaid to the death of Aed had to be accounted for. The recorded regnal years were insufficient, and the defect was supplied by an impossible interpolation in the sixth century, whereas it was in the fifth century, in the period anterior to Duach, that the supplement was chiefly needed. Having established this point, we need not consider further the succession of kings subsequent to Duach Tenga Uma.
It is clear that there was a definite tradition assigning to Amolngaid twenty years, to Ailill Molt eleven years, and Duach twenty years; and that the chronologer, whom O’Duinn followed, did not venture to tamper with these numbers in order to account for the missing years. As for Ailill Molt, twenty years are assigned to him in the list in the Book of Leinster. But this may be at once rejected; for twenty years represent the duration of his reign as king of Ireland (462-482), and it is highly improbable that the throne of Connaught became vacant at the same moment as the throne of Ireland. Accepting then eleven years as the genuine tradition, he must have succeeded to Connaught c. 471, as he died in 482, and there is no reason to suppose that he resigned the kingship of Connaught before his death. The interval from 482 to 502 is exactly covered by the twenty years assigned to Duach Tenga Uma. If Amolngaid followed Dathi in 428 and reigned for twenty years, the end of his reign would fall c. 448, which would correspond to the record in the Annals of the Four Masters (449). Thus we should arrive at an interval of about twenty-four years between Amolngaid’s death and Ailill Molt’s succession (448-471), which is unaccounted for. [The confusion of Ailill Molt’s regnal years in Connaught with his twenty regnal years in Ireland served to shorten this period by nine years; and in the list of the Book of Leinster the residue of the chronological error is “corrected” by adding fourteen years to the reign of Amolngaid, to whom thirty-four years are assigned.]
The question therefore is, who reigned in Connaught between Amolngaid and Ailill Molt? Now I think it can hardly be insignificant that in the Annals as well as in the lists Duach Tenga Uma is reduplicated. This must have had some motive, and the most probable explanation seems to be that two Duachs did reign in Connaught, and that O’Duinn is right in distinguishing Duach son of Brian from Duach son of Fergus, though he confuses the order and chronology. For it is clear that he had knowledge of Duach Galach son of Brian, whom he describes as falling in battle with the Cinel Eogain. His notice of this king is as follows (I use the text and translation furnished by Mr. E. J. Gwynn):—