This new jarl, the second founder of the line of Orkney jarls, conquered Caithness and Sutherland as far south as Ekkjals-bakki,[7] which is believed by some to be in Moray, and by others, with more truth, to be the ranges of hills in Sutherland and Ross lying to the north and to the south of the River Oykel and its estuary, the Dornoch Firth; and the second part of the name still happens to survive in the place-name of Backies in Dunrobin Glen and elsewhere in Cat where the Norse settled. About the year 890,[8] after challenging Malbrigde of the Buck-tooth to a fight with forty a side, to which he himself perfidiously brought eighty men, Sigurd outflanked and defeated his adversary, and cut off his head and suspended it from his saddle; but the buck-tooth, by chafing his leg as he rode away from the field, caused inflammation and death, and Jarl Sigurd's body was laid in howe on Oykel's Bank at Sigurthar-haugr, or Sigurds-haugr, the Siwards-hoch of early charters now on modern maps corruptly written Sidera or Cyderhall, near Dornoch, which, when translated, is Sigurd's Howe.[9] "Thenceforward," as Professor Hume Brown tells us, "the mainland was never secure from the attacks of successive jarls, who for long periods held firm possession of what is now Caithness and Sutherland. As things now went, this was in truth in the interest of the kings of Scots themselves. To the north of the Grampians they exercised little or no authority; and the people of that district were as often their enemies as their friends. Through the action of the Orkney jarls, therefore, the Scottish kings were at comparative liberty to extend their territory towards the south; and the day came when they found themselves able to crush every hostile element even in the north.[10] It is this process of consolidation in the north which it is proposed to describe so far as Sutherland and Caithness are concerned, using both Norse and Scottish records, and piecing them together as best we can, and, be it confessed, in many cases filling up great gaps by necessary guess-work when records fail. In the reign of the great king Constantine III, between the years 900 and 942, the Danes again gave trouble. In 903 the Irish Danes ravaged Alban,[11] as Scotland north of the Forth was then called, for a whole year; in 918 Constantine and his ally, Eldred of Lothian, were defeated by another expedition of these invaders; and in 934 Athelstan and his Saxons burst into Strathclyde and Forfar, the heart of Constantine's kingdom, and the Saxon fleet was sent up even to the shores of Caithness, as a naval demonstration intended to brave the Norse, who had joined Constantine, on their own element. Lastly, in 937 Athelstan and Constantine met at Brunanburg, probably Birrenswark near Ecclefechan, and Constantine and his Norse allies were completely defeated.[12]