Angus MacFergus, that the new and disturbing influence mentioned above
appeared in force in Alban. Favoured in their voyages to and fro by
the prevailing winds, which then, as now, blew from the east in
the spring and from the west later in the year, the Northmen,
both Norsemen and Danes, neither being Christians, had, like their
predecessors the Saxons and Angles and Frisians, for some time made
trading voyages and desultory piratical attacks in summer-time on
the coasts of Britain and Ireland, and probably many a short-lived
settlement as well. But as these attacks and settlements are
unrecorded in Cat, no account of them can be given.

In 793 it is on record that the Vikings first sacked Iona, originally
the centre of Columban Christianity but then Romanised, and they
repeated these raids on its shrine again and again within the next
fifteen years. Constantine thereupon removed its clergy to Dunkeld,
"and there set up in his own kingdom an ecclesiastical capital for
Scots and Picts alike,"[1] as a step towards the political union
of his realm, which Norse sea-power had completely severed from the
original home of the Scots in Ulster.

The Northmen now began the systematic maritime invasions of our
eastern and northern and western coasts and islands, which history has
recorded. North Scotland was attacked almost exclusively by Norsemen,
and Norsemen and Danes invaded Ireland. The Danes seized the south of
Scotland, and the north of England, of which latter country, early in
the eleventh century in the time of King Knut, they were destined to
dominate two-thirds, while Old Norse became the _lingua franca_ of
his English kingdom, and enriched its language with hundreds of Norse
words, and gave us many new place and personal names.