The most southern point of Dunrossness, on Mainland, forms the promontory of Sumburg Head (“Sunnbœjar-höfði”), which, however, is of no very great height; indeed the highest mountain in Shetland is only about fifteen hundred feet above the sea. Although the Shetland Islands, with regard to mountains, are not to be compared with the Faroe Isles, still they exhibit a sort of transition from the flatter Orkneys to the mountainous character of the Faroe group. Before the coasts of Shetland stand many high and ragged rocks, called “stacks” (old Norsk, “stackr”). The coasts themselves are steeper, and the mountains larger than in the Orkneys. On the other hand, however, the valleys are both longer and broader than the mountain valleys of the Faroe Islands. Heath and moorland abound, whilst the corn-fields are small, and the corn harvest in general very uncertain and difficult to gather. Fishing is the most important source of profit for the inhabitants. The Orkneys and the Shetland Isles were, as is well known, completely colonized by Norwegians in the ninth and tenth centuries. They were, however, known and inhabited much earlier. It is possible that the Shetland Islands were the “ultima Thule” spoken of by Roman authors in the first centuries after Christ; but it is certain that the Romans at that time knew the Orkneys by the name of “Orcades:” whence it appears that the primitive root _Ork_, in the later Norwegian name of the islands, is very ancient, and probably of Celtic origin. Before the arrival of the Norwegians, both the Orkneys and the Shetland Islands seem to have been inhabited by the same Pictish or Celtic race that was settled in the rest of Scotland. Of these older inhabitants memorials still exist in different kinds of antiquities of stone and bronze that are dug out of the earth, as well as in numerous ruins of castles, or Pictish towers, originally built of flag-stones laid together, without any cement of loam or mortar. There are also cairns and stone circles; the most prominent amongst which are the “Stones of Stennis,” on each side of Brogar Bridge, in Orkney. They are, like Stonehenge and Abury circle in England, surrounded with ditches and ramparts of earth; and, after Stonehenge, must be regarded as amongst the largest stone circles in the British Islands. The immense masses of erect stones are remarkable evidences both of the strength and of the religious enthusiasm of the old Celtic inhabitants; and it is no wonder that they made in ancient times such an impression on the Norwegians, on their arrival at these islands, as to induce them to call the promontory on which the largest circle stands “Steinsnes” (Stones-naze) and the adjoining firth, “Steinsnesfjördr” (Stones-naze Firth, now Loch of Stennis).