By the physical structure of the country, there run out from a solid centre of mountain-land a multitude of rocks, like great prongs, with deep gulfs between them filled from the sea. These are the celebrated Fiords, which send branches or inlets through the mountains on either side, some of them longer than the longest sea lochs of the West Highlands of Scotland. Except in the few places where large rivers make deltas of silt, the rocks run sheer down into deep water, so that vessels can lie close to the land in the smallest crevices or bays. The entrances to wide stretches of fiord are sometimes so narrow, and consequently so easily defended, that the people speak of the stones rolling from the tops of the high rocky banks, and bounding across the water, so as to strike the opposite shore. It was of little consequence to the Vikings that the soil around them was hard and barren, for the value to them of that soil was in protection, not in produce. The only articles they required for home industry were the timber, iron, and pitch, for the building of their vessels, and the fish which abounded in their narrow seas. All their other wants were provided by plunder from the industrious and affluent communities of other lands. In the Hebrides and the sea-lochs of the Highlands they found harbours of retreat the same in character, though not in greatness, as those they left behind them; and we may fairly suppose that it was for these, not necessarily for any temptation in the prospect of plunder, that those districts were frequented by them. Hence it was that the Orkney and other Northern Isles, and even a great part of the north of Scotland, came in hand more naturally to the monarch ruling in Norway than to the king of the Scots. When we find these sea-rovers in the north-west of Scotland and in Ireland, it becomes obvious, and is confirmed by facts, that they took the north-east coast of Scotland and the northern islands in their way. As the Shetland Islands are not more than two hundred miles distant from the mouths of two of their greatest fiords—the Hardanger and the Sogne, it may be inferred that these islands, or Caithness, was their first landfall, where they could swarm off to the Faroes or Iceland, on the one side, or to Scotland, England, and Ireland, on the other. [Sidenote: Great skill as seamen.]