It is usually supposed that true history in Ireland commences with the introduction of Christianity and the mission of St. Patrick, but this date is by no means certain. The author is more inclined to place the separation between those annals which may be depended on as consisting in the main of true history, and those which present the appearance of an artificial construction, into which fragments of history, legendary matter, and fabulous creations, have been interwoven, at the event termed the battle of Ocha, fought in 483. By that battle the dynasty of the Hy Neill was placed on the throne of Ireland. It separates the Pagan kings from the Christian. The marvellous and fanciful events which characterise the previous reigns here drop from the annals, and what follows has an air of probability and reality, and it was undoubtedly viewed as a great era by the older chroniclers; as, for instance, Flann of Bute, who wrote his Synchronisms in 1054, has ‘Forty-three years from the coming of St. Patrick to Erin to the battle of Ocha; twenty years from the battle of Ocha till the children of Erc, son of Echach Muindremair, passed over into Alban.’—_Chron. Picts and Scots_, p. 18. Footnote 18: The author has explained his views as to the authorities for this period of the history more anxiously, because he does not at all sympathise with Mr. Burton in his view of the authority of Tacitus as an historian, and the character of his narrative. The author is unable to see how the credibility of his narrative is impaired by the fact that his Life of Agricola was not included in the first edition of his works, and was unknown to our historians before Hector Boece. Mr. Burton hardly ventures to question the authenticity of the Life of Agricola. The view he appears to hold, that it was written more as a political manifesto than as a plain historical relation of facts, has been hastily adopted from a school of German critics, whose views have not, however, met with acceptance from the sounder class of them. The author holds the authenticity of the Life of Agricola to be unquestionable, and that its fidelity as a narrative cannot be reasonably assailed; and he considers any argument drawn from the presence or absence of local tradition as to the events it records to be irrelevant, as all genuine tradition of this kind in Scotland has perished under the influence of the immense popularity and general acceptance at the time of Hector Boece’s fabulous history, which has, in fact, created a spurious local tradition all over Scotland. BOOK I. _HISTORY AND ETHNOLOGY._ CHAPTER I. ADVANCE OF THE ROMANS TO THE FIRTHS OF FORTH AND CLYDE. [Sidenote: Early notices of the British Isles.]