Note 25 — Chapter XXXII

In the "Master of the Rolls" Series, in 1867. "That the work was compiled from contemporary materials," says Dr. Todd, "may be proved by curious incidental evidence. It is stated in the account given of the Battle of Clontarf that the full tide in Dublin Bay on the day of the battle (23rd April, 1014) coincided with sunrise, and that the returning tide at evening aided considerably in the defeat of the enemy. It occurred to the editor, on considering this passage, that a criterion might be derived from it to test the truth of the narrative and of the date assigned by the Irish Annals to the Battle of Clontarf. He therefore proposed to the Rev. Samuel Haughton, M.D., Fellow of Trinity College, and Professor of Geology in the University of Dublin, to solve for him this problem: 'What was the hour of high water at the shore of Clontarf in Dublin Bay on the 23rd of April, 1014.' The editor did not make known to Dr. Haughton the object he had in view in this question, and the coincidence of the result obtained with the ancient narrative is therefore the more valuable and curious."

Dr. Haughton read a paper on the mathematics of this complex and difficult question before the Royal Irish Academy, in May, 1861, in which he proved that the tide—a neap tide—was full along the Clontarf shore at about 5h. 30m. a.m., and that the evening tide was full in about 5h. 55m. p.m. "The truth of the narrative," says Dr. Todd, "is thus most strikingly established. In the month of April the sun rises at from 5h. 30m. to 4h.30m. The full tide in the morning therefore coincided nearly with sunrise; a fact which holds a most important place in the history of the battle, and proves that our author if not himself an eye-witness, must have derived his information from those who were. 'None others,' as Dr. Haughton observes, 'would have invented the fact that the battle began at sunrise and that the tide was then full in. The importance of the time of tide became evident at the close of the day, when the returned tide prevented the escape of the Danes from the Clontarf shore to the north bank of the Liffey.'"