124 MAMMALS

them ;’ they manage to swim upright without a fin
to their back, and they have no wrinkles about the
throat. The rorquals (vork-wals) are the whales with
the ‘rorks’ or wrinkles under the throat ; they have a
longish back-fin somewhat like a hook in shape; and
they feed chiefly on codfish. Intermediate between
these are the grey whale of the North Pacific with
no fin on the back, the pigmy whale of Australasia
with a very small back-fin and a smooth throat-skin,
and the humpback whale of most seas, with a rather
larger back-fin and a wrinkled throat-skin, the fin
rising from a sort of hump, the animal’s head being
proportionately larger than among the rorquals. The
baleen whales can be distinguished from the others at
a glance by the way they ‘blow.’ The nostrils of a
baleen whale are at the top of his. head, and he spouts
vertically, while the nostrils of the others are at the
tip of their snout, and they spout diagonally forwards
—the spouting being, it need hardly be said, the
humid heated air expelled from the lungs, which
condenses as it ascends and often takes some of the
surface water up with it. The whale only blows when
he rises and just before he dives, at other times he
will float at his ease on the surface, breathing quietly
like any other mammal. The Greenland whale blows
for seven times or more, and then dives for a quarter of ©
an hour, although a harpooned whale has been known
to stay under water for fifty minutes. This whale,
like all the right whales, is never very brisk in his
movements. His ordinary swimming speed is four
miles an hour, with a power of working up to eight
-in times of peril. The rorquals are a much more