once; but if after inhaling, it does not sink for
some little time afterwards. The inhaled air
delays the sinking. These facts prove that the
floating in water and in air depends upon the
inhaling of air. But a bird, we are told, when
floating in the air, is still heavier—immensely
heavier—than the air. There is a begging of
the question here. We have no means of weighing
a bird when floating in the air, and the
physiologists go no further than to say that the
bird, like the seal, is relatively lighter when full
of air. Heavy birds cannot immediately rise on
the wing. This is why the albatross fell down.
The only free eagle I ever saw was sitting on
the top of the ruins of a Highland castle, and,
after allowing me to walk quite near it, the eagle
took wing in a lubberly way, descending slowly
towards the water of the loch before rising to
fly over the mountain opposite. Mr. Wenham,
author of a paper published by the Aëronautical
Society, describes the rising of an eagle as he
saw it in Egypt. The eagle let him approach
within eighty yards without stirring. A few
feet nearer, and then the eagle began to walk
away with expanding but motionless wings.
A charge of shot rattles upon his feathers. His
walk increases to a run; his feet-marks, from
digs, become long scratches of his claws, a run
of full twenty yards being necessary to enable
him to lighten his body, get up his steam, and
inflate his gas-bags and pipes before he could,
although spurred by shot, rise on the wing.

Pelicans, according to the same observer, also
rise from the ground with difficulty. A specimen
weighed twenty-one pounds, and the wings
measured ten feet, from tip to tip. A flock of a
hundred pelicans fly after a leader one by one,
looking like a long undulating ribbon glistening
under the sun in a cloudless sky. High up
they float serenely, as if asleep, for hours, a
few easy strokes a minute sufficing to sustain
them at their level.

Seals we have seen float or sink as they have
inhaled or exhaled air. Heavy birds require
time before they can rise from the ground.
Fish, I may add, have gas-bags to make them
buoyant in water. Birds which are not built
to hold much gas do not fly, and the powers of
those that fly are proportional, and their modes
of flight are in accordance with the ratios of
their gaseousness and the plans of its distribution.
Pigeons prove these propositions
marvellously well. Pigeons differ in size, there
being kinds little smaller than turkeys, and
other species little larger than sparrows; whilst
as regards flight, the carrier-pigeon can fly a
mile in a couple of minutes, and the Manumea
(Didunculus strigirostris) cannot fly out of the
reach of cats. The Dodo is an extinct species
of pigeon, because its structure, adapted for
much flesh and little gas, made its body heavier
than its wings could hoist into the air. The
Duke of Argyll ascribes flight to the force of
the downward strokes of the wings. If this
were so, the powers of flight would be
proportional to the areas of the wings, which is
not the fact, for pheasants with large wings are
comparatively poor flyers, while ducks, with
comparatively small wings, are strong flyers.
The wild duck has only seventy-two inches
to the pound, or little more than half the
wing surface it ought to have, according to
Smeaton's Table of Resistances.* Carrier-pigeons,
tumblers, and rollers behave differently,
according to the differences of structure
which distribute their gases, their internal gas-pipes,
called bones, and their external gas-tubes,
called feathers. The wings of the pigeon and
the pelican have been objects of much admiration:
the stiff hard front edge, the rigidity of
the pen, the elasticity of the plume, and the
webs, the adaptation of the edge for catching
hold of the undisturbed layers of air, and of the
concave shape of the wing, and wide spread of
the feathers for obtaining a propelling push;
and these peculiarities are most remarkable in
the kinds of pigeons which can fly for eight
hours at a stretch, at the rate of forty-five miles
an hour. But the tumblers and rollers are not
less remarkable than the carriers. Tumblers
throw themselves backwards in the air
sometimes, as if they were tying a knot or weaving
braid or whiplash. The rollers are a variety of
the pigeons who roll themselves down, or fall
down heads over tails from the sky. They
sometimes hurt themselves on striking the ground.
Mr. Brent—an authority on the subject—says
these pigeons tumble because their real does not
coincide with their apparent centre of gravity.
Indian jugglers throw balls up into the air,
which whirl about, because they are weighted
with lead at a particular spot inside. When
the cerebellum of a pigeon has been removed,
the bird loses its power of maintaining its
equilibrium and regulating its movements. The
tumbler falls backwards because its head is
light and its body heavy. Every part of the
carrier is long, and every part of the tumbler is
short, beak, head, neck, body, wings, and tail.
The tumbler has even one primary quill fewer
than the carrier.
* See Mr. Wenham's calculations.

There is a kind of roller which rolls on the
ground. The varieties called house-tumblers
are merely tumblers which have tumbled until
they have become unable to fly, and which when
forced up fall topsy turvy once or twice and
then settle down again. Mr. Brent says, if
tossed in a handkerchief, they will tumble over
every time they feel it descend. But the
Lowtans of India can be made to roll heads over
tails on the ground. The filliped Lowtan is
rubbed on the head, and then on getting a fillip
it will roll on the ground imtil taken up. There
is a knack which only the initiated know in
making them roll. A Mussulman policeman, on
being told to make one tumble, placed his hand
on the back, put his first and second fingers
on either side of the neck, and shook the bird
four or five times sideways. When put on
the ground, the Lowtan "rolled backwards so
quickly that the eye could not follow it."
"Alter what I judged to be a dozen tumbles"
says the reporter of the scene, "he took it up
and breathed upon its head (why, I know not),