One of the principal products of the Greenland whale is its baleen, or whalebone, with the domestic uses of which our readers will be familiar; but the large quantities of oil which it yields are still more valuable. A whale sixty feet in length will supply fully twenty tons of pure oil. Besides the common whale, our hunters find in the seas of the North the razor-backed whale, or northern rorqual (_Balænoptera physalis_), characterized by the prominent ridge which extends along its mighty back. This monster of the deep attains a length, it is said, of one hundred feet, and measures from thirty to thirty-five feet in circumference. But its yield of oil and baleen is less than that of the right or Greenland whale, and as its capture is a task of difficulty and danger, the whalers seldom attack it. In its movements it is more rapid and restless, and when harpooned it frequently plunges downward with such force and velocity as to break the line. In several respects it differs from the Greenland species; and particularly in the nature of its food, for it feeds upon fishes of considerable size. Some of our naturalists affirm that several species of rorquals exist in the Arctic seas; and the pike whale, so called from the resemblance of its mouth to that of a pike, is frequently described as an independent species. Others, however, are of opinion that the pike is simply the young of the monster we have been describing. The rorqual is very voracious, and preys extensively upon fishes; as many as six hundred cod, to say nothing of smaller “fry,” having been found in the stomach of a single individual. While the Greenland whale is being rapidly driven back into the icy wildernesses beyond Behring Strait, on the west, and the creeks and gulfs beyond Baffin Bay, on the east, the rorquals, including the _Balænoptera rostratus_ (or beaked whale), _Balænoptera musculus_, and _Balænoptera boöps_, still frequent the open waters,--their pursuit being, as we have shown, more difficult and less profitable. They are generally found in attendance on the herring-shoals, of which they are the assiduous and destructive enemies. Off Greenland, Spitzbergen, and Novaia Zemlaia they are found in considerable numbers.