As in Ireland and Wales, so also in Scotland, the ancient measures of land were closely connected with the tribal system, but here too we find them more greatly affected by external influences than in the two former countries. When we examine the most ancient land-measures of that part of Scotland lying north of the Firths of Forth and Clyde, we do not find the same local varieties which can be traced in the different provinces of Ireland and Wales, but instead, a great and leading difference between those of the eastern and the western districts. In the eastern districts there is a uniform system of land denominations consisting of Davachs, Ploughgates, and Oxgangs, the davach consisting of four ploughgates, and each ploughgate of eight oxgangs; but as soon as we cross the great chain of mountains separating the eastern from the western waters, we find a different system equally uniform. The ploughgates and oxgangs disappear, and in their place we find davachs and penny lands. The portion of land termed a _davach_ is here also called a _Tirung_ or ounce land (_unciata terra_), and each davach or _Tirung_ contains twenty penny lands. The davach[266] being the only denomination common to both parts of the country, we may infer that it belongs to the old Celtic system of land-measures, and that the others are foreign importations. Now we find in the ancient province of Lothian, which originally formed part of the Anglic kingdom of Northumbria and possessed an Anglic population, the land-measures consisted of Carucates or ploughgates, and Bovates or oxgangs. The oxgang contained thirteen acres, two oxgangs made a husband-land, and eight oxgangs a ploughgate, which thus consisted of 104 acres of arable land. On the other hand, in the islands of Orkney and in the district of Caithness, which were formerly a Norwegian earldom under the king of Norway, we find the land was valued according to a standard of value derived from the weight of silver, the unit being the ounce or _Eyrir_, eight ounces forming the _Mörk_ or pound, and twenty pennings one ounce,[267] and thus the land-measures consisted of _Oers_ or ounce lands, the ounce lands containing either eighteen or twenty penny lands. They seem to have been so called, because under the Norwegian rule each homestead paid one penny as _scat_.