moreover, shown that temperature does not
descend, as was supposed, in ratios proportional to
elevation, but goes down according to different
ratios in different strata of air. On the 29th of
May, 1866, Mr. Glaisher, by ascending and
descending once before and once after sunset,
obtained results strikingly contradictory to the old
views, for he ascertained that after sunset the
temperature rises at great elevations. Before
sunset, at a height of six thousand one hundred
feet, the temperature was twenty-seven degrees
colder than at Greenwich; and after sunset, the
temperature at six thousand two hundred feet
was five degrees higher than before, whilst it
had gone down two degrees at Greenwich.

Mr. James Glaisher found the balloon degraded
to a sensational plaything, and he has restored it
to science as a floating observatory. He is giving
us real instead of conjectural knowledge of the
aërial ocean. He has moreover, taken up the
question of all ages and tribes, How may man,
the naked featherless biped, fly?

The British Flying Society—I beg pardon,
the Aëronautical Society of Great Britain—of
which Mr. Glaisher is the treasurer, have asked
naturalists to tell them, more clearly than they
have yet been told, how birds and insects fly?
"When we consider," says Mr. Glaisher, "that
the act of flying is not a vital condition, but
purely a mechanical action, and that the animal
creation furnishes us with models of every size
and form, from the minutest microscopic insect
to the bird that soars for hours above the
highest mountain range, it seems remarkable
that no correct demonstration has ever been
given of the combined principles upon which
flight is performed, nor of the absolute force
required to maintain that flight." The president
of the society, the intelligent Duke of
Argyll, is still more dissatisfied with the
physiologists: "The mechanical principles upon
which flight is achieved is a subject which has
scarcely ever been investigated in a scientific
spirit. In fact, you will see in our best works
of science, by the most distinguished men, the
account given of the anatomy of a bird is that
a bird flies by inflating itself with warm air, by
which it becomes buoyant like a balloon. The
fact is, however, that a bird is never buoyant.
A bird is immensely heavier than the air. We all
know that the moment a bird is shot it falls to
the earth; and it must necessarily do so,
because one of the essential mechanical principles
of flight is weight; without it there can be no
momentum, and no motive force capable of
moving through atmospheric currents."

These extracts are specimens of the way in
which engineers and mechanicians call aloud to
naturalists and physiologists for models upon
which they may make machines, and after the
models are obtained, the acknowledgments of the
receivers are very seldom heard. There is no
protection or copyright for physiological
discoveries. As for the remarks of the heroic
air-sailor and the noble duke, they seem to show, I
most respectfully submit, that they have not
mastered the teachings of physiology on the
subject of flight.

What is the physiological idea of a bird?
"One of the most striking peculiarities of
birds," say Siebold and Stannius, "is the
pneumaticity of a greater or less number of the
bones of which they are composed, that is to
say, the absence of marrow in the diploïque
(the spongy substance between the two tables
of the skull), or the presence, in the interior of
the bones, of canals which communicate by
openings with the organs which receive air. Air
penetrates by two ways into the cranial bones—
through the Eustachian tube and the nostrils.
It makes its way into the trunk and the
extremities chiefly by the aërial pouches peculiar to
this class of animals, which occupy the greater
part of the visceral cavity, often extending even
beyond it, and communicating by large openings
through the bronchial tubes with the surface of
the lungs; in the pelicans, as Owen as justly
remarked, to the extremities of the femur and
the wings."

Thus far Siebold and Stannius. The anatomist
who examines birds of high or long flight
finds bags, tubes, pipes, holes, receptacles for
gas, inside them everywhere—in the skull,
backbone, and tail, humerus and femur, and toes.
The long wing-bones of the albatross are made
into pipe-stalks. The inner frame of the bird
is, then, viewed as a flying-machine, composed
of gas-bags, gas-pipes, gas-holes, and crannies on
which the joints and muscles, or ropes and
pulleys, of the outside machinery work and play.
Some birds (the Coraciadæ, or Toddies Rollers,
&c.) have air-cells in their skins. The bones of
birds are lighter than those of mammals. The
poet, James Montgomery, viewed the skeleton
of the large pelican with wonder:

Their slender skeletons ....
So delicately framed, and half transparent,
That I have marvelled how a bird so noble,
When in his full magnificent attire,
With pinions wider than the king of vultures,
And down elastic, thicker than the swan's,
Should leave so small a cage of ribs to mark
Where vigorous life had dwelt a hundred years.

The skin of birds is covered with innumerable
gas-tubes, called feathers, which are held in
sheaths and kept warm by their arrangement
and their appendages of down and web.

Birds, no doubt, fall to the ground when
shot; and there can be no doubt, also, of their
floating like a buoy, or of their buoyancy. But
it is not merely when dead that they fall to the
ground. Captain Carmichael having taken a
sooty albatros by the wings and pitched it over
a rock, it fell like a stone, although it had
several hundred feet of clear fall to recover
itself in. Seals fall to the bottom, when shot,
as birds fall to the ground. When seals enter
the mouth of the river Don, in Aberdeenshire,
the fishermen place nets across the river to
prevent the bodies of the shot seals from being
carried out to sea. Mr. Lloyd records that the
Scandinavian seal-hunters place small buoys
above the spot where a shot seal sinks; and
Blomquist, an old hunter, told Mr. Lloyd that,
if shot after exhaling, the seal goes down at