ter
emphasis. The moment the animal rises to the surface it forcibly expels
from its lungs the air taken in at the last inspiration, which is
charged with vapour in consequence of the respiratory changes. This
rapidly condensing in the cold atmosphere in which the phenomenon is
often observed, forms a column of steam or spray, which has been taken
for water. It happens, however, especially when the surface of the ocean
is agitated into waves, that the animal commences its expiratory puff
before the orifice has cleared the top of the water, some of which may
thus be driven upwards with the blast, tending to complete the illusion.
From photographs of spouting rorquals, it appears that the height and
volume of the "spout" of all the species is much less than was supposed
to be the case by the older observers; even that of the huge
"sulphur-bottom" (_Balaenoptera sibbaldi_) averaging only about 14 ft.
in height, although it may occasionally reach 20 ft.

As regards their powers of hearing, the capacity of cetaceans for
receiving (and acting upon) sound-waves is demonstrated by the practice
of shouting on the part of the fishermen when engaged in driving a shoal
of porpoises or black-fish into shallow water, for the purpose of
frightening their intended victims. As regards the possession of a voice
by cetaceans, it is stated that one species, the "buckelwal" of the
Germans, utters during the breeding-season a prolonged scream,
comparable to the scream of a steam-siren, and embracing the whole
musical scale, from base to treble. In respect of anatomical
considerations, it is true that the external ear is much reduced, the
"pinna" being absent, and the tube or "meatus" of very small calibre. On
the other hand, the internal auditory organs are developed on the plan
of those of ordinary mammals, but display certain peculiar modifications
(notably the remarkable shell-like form of the tympanic bone) for
intensifying and strengthening the sound-waves as they are received from
the water. It seems, therefore, perfectly evident that whales must hear
when in the water. This inference is confirmed by the comparatively
small development of the other sense-organs. The eye, for instance, is
very small, and can be of little use even at the comparatively small
depths to which whales are now believed to descend. Again, the sense of
smell, judging from the rudimentary condition of the olfactory organs,
must be in abeyance; and whales have no