These earlier retreats served as so many houses of refuge for the poor monks and scholars flying from the fury of the Norsemen, when life and property became insecure at home, in Iona, and elsewhere. It is known that a fresh tide of Gaelic pilgrims set out for the Continent from the time that the new peril appeared, seeking safe custody for themselves and their books among their countrymen abroad. And thus it has come to pass that there are to-day hundreds of Celtic MSS. in Latin and Gaelic widely scattered throughout Europe, in places as far apart as Paris, Brussels, Dresden, Berne, Vienna, Rome, Florence, Milan, Schaffhausen, St. Gall, etc. And while in the British Isles we have only seven of these with Gaelic writing prior to the eleventh century, on the Continent there are as many as twenty. It is surmised that it was in this manner in 825, after the attack on Iona and murder of St. Blathmac, that the famous _Vita Columbæ_ of Adamnan found its way to Reichenau on the Rhine, where it remained for nearly a millennium, till it was ultimately transferred to Schaffhausen. These are two far-reaching and long-lasting effects of the Viking troubles—the arrest of the literary development and the dispersion of the documents, but they by no means exhaust the category. III. We have now to take into account the severance of Ireland from Scotland. Anterior to the Norse invasions the language and literature of both were one. There is no distinction to be made, for they were common to both countries from the time of St. Columba, and there was constant coming and going between Scotland and Ireland. But when the Norsemen came they effectually put a stop to this. For two centuries they kept the kindred realms apart, and never again was the original unity restored. During the period of disjunction the separated parts began to travel on different lines, and when the Viking sway ceased to sever them, the language and literature of each had already taken on a character of its own sufficiently divergent to keep them for ever asunder. The Book of Deer is the first monument of this departure in Scotland, even as the Leabhar Na h’Uidhre and _Liber Hymnorum_ are the earliest in Ireland. The Norse invasions were thus directly responsible for the rise of the Scottish Gaelic and our native vernacular literature as distinct from the Irish. Had it not been for their interception there is no knowing how long the two dialects might have continued as one. As it was, notwithstanding the growing divergence, the written, though not the spoken language of both countries might be regarded as still, for the most part, the same in form till the fourteenth century. After that they ceased to be even apparently identical, and to-day the chief differences between the two tongues are these four:— 1. The Irish has a future in the verb, whereas Gaelic uses the present tense to indicate futurity. 2. Inflection is fuller in written Irish than in written Gaelic.