Even the white-bear is said to attack the whale, watching his approach to the sea-shore; but the enmity of the narwhal is evidently fabulous, as both cetaceans may frequently be seen together in perfect harmony. Besides these formidable attacks of what may be considered as more or less noble foes, the whale is constantly harassed by the bites of the vilest insects. A large species of louse adheres by thousands to its back, and gnaws this animated pasture-ground, so as to cover it frequently with one vast sore. In the summer, when this plague is greatest, numbers of aquatic birds accompany the whale, and settle on his back, as soon as it appears above the water, in order to feed upon these disgusting parasites. [Illustration: Whale Louse.] Barnacles often cover the whale in such masses, that his black skin disappears under a whitish mantle, and even sea-weeds attach themselves to his vast jaws, floating like a beard, and reminding one of Birnam's wandering forest. As its name testifies, the home of the Greenland whale is confined to the high northern seas, where it has been met with in the open waters or along every ice-bound shore as far as man has penetrated towards the Pole. The southern limit of its excursions seems to be about 60° N. lat. It never visits the North Sea, and is seldom found within 200 miles of the British coasts. Its favourite resorts are the so-called whale-grounds,[K] between 74° and 80° N. lat., where the warmth, imparted to the water by the Gulf-stream, favours the multiplication of the small marine animals which form the nourishment of the Leviathan of the seas. [Footnote K: See page 20.] Sometimes open spaces in the ice, abounding in minute crustaceans and medusæ, attract a larger number of whales, but the huge creature cannot be said to live in larger herds or associations. The Fin-fish or northern Rorqual (_Balænoptera boops_, _musculus_) attains a greater length than the sleek-backed Greenland whale, but does not equal it in bulk, having a more elongated form and a more tapering head. Its whalebone is much shorter and coarser, being adapted to a different kind of food, for, despising the minute medusæ and crustaceans which form the food of its huge relation, the more nimble rorqual pursues the herring and the mackerel on their wandering path. Like the blubber-whale, the fin-back is black above, white below, but distinguishes itself by long and numerous blood-red streaks or furrows, running under the lower jaw and breast as far as the middle of the belly. This is the species of whale which not unfrequently strands on our shores, for though an inhabitant of the Arctic seas, it wanders farther to the south than the Greenland whale. It is seldom harpooned, for the produce of oil is not equivalent to the expense, the risk, and the danger attending its capture.