Taken as a whole, one may fairly say that the total population of the British Isles consists mainly of three great elements. The first and oldest--the only one with any real claim to be considered as truly native--is the cold Northern, Alpine and Arctic element, comprising such animals as the white hare of Scotland, the ptarmigan, the pine marten, and the capercailzie--the last once extinct, and now reintroduced into the Highlands as a game bird. This very ancient fauna and flora, left behind soon after the Glacial Epoch, and perhaps in part a relic of the type which still struggled on in favoured spots during that terrible period of universal ice and snow, now survives for the most part only in the extreme north and on the highest and chilliest mountain-tops, where it has gradually been driven, like tourists in August, by the increasing warmth and sultriness of the southern lowlands. The summits of the principal Scotch hills are occupied by many Arctic plants, now slowly dying out, but lingering yet as last relics of that old native British flora. The Alpine milk vetch thus loiters among the rocks of Braemar and Clova; the Arctic brook-saxifrage flowers but sparingly near the summit of Ben Lawers, Ben Nevis, and Lochnagar; its still more northern ally, the drooping saxifrage, is now extinct in all Britain, save on a single snowy Scotch height, where it now rarely blossoms, and will soon become altogether obsolete. There are other northern plants of this first and oldest British type, like the Ural oxytrope, the cloudberry, and the white dryas, which remain as yet even in the moors of Yorkshire, or over considerable tracts in the Scotch Highlands; there are others restricted to a single spot among the Welsh hills, an isolated skerry among the outer Hebrides, or a solitary summit in the Lake District. But wherever they linger, these true-born Britons of the old rock are now but strangers and outcasts in the land; the intrusive foreigner has driven them to die on the cold mountain-tops, as the Celt drove the Mongolian to the hills, and the Saxon, in turn, has driven the Celt to the Highlands and the islands. Yet as late as the twelfth century itself, even the true reindeer, the Arctic monarch of the Glacial Epoch, was still hunted by Norwegian jarls of Orkney on the mainland of Caithness and Sutherlandshire.