higher animals, and expect it to be best defined in those which were
best known. And being referred for satisfaction to the 226th page of
the first volume of Mr. Darwin's "Descent of Man," he would find this
passage:--
"Man has been studied more carefully than any other organic being, and
yet there is the greatest possible diversity among capable judges,
whether he should be classed as a single species or race, or as two
(Virey), as three (Jacquinot), as four (Kant), five (Blumenbach), six
(Buffon), seven (Hunter), eight (Agassiz), eleven (Pickering), fifteen
(Bory St. Vincent), sixteen (Desmoulins), twenty-two (Morton), sixty
(Crawford), or as sixty-three according to Burke."
And in the meantime, while your men of science are thus vacillating, in
the definition of the species of the only animal they have the
opportunity of studying inside and out, between one and sixty-three;
and disputing about the origin, in past ages, of what they cannot
define in the present ones; and deciphering the filthy heraldries which
record the relation of humanity to the ascidian and the crocodile, you
have ceased utterly to distinguish between the two species of man,
evermore separate by infinite separation: of whom the one, capable of
loyalty and of love, can at least conceive spiritual natures which have
no taint from their own, and leave behind them, diffused among
thousands on earth, the happiness they never hoped, for themselves, in
the skies; and the other, capable only of avarice, hatred, and shame,
who in their lives are the companions of the swine, and leave in death
nothing but food for the worm and the vulture.
62. Now I have first traced for you the relations of the creature we
are examining to those beneath it and above, to the bat and to the
falcon. But you will find that it has still others to entirely another
world. As you watch it glance and skim over the surface of the waters,
has it never struck you what relation it bears to the creatures that
glance and glide _under_ their surface? Fly-catchers, some of
them, also,--fly-catchers in the same manner, with wide mouth; while in
motion the bird almost exactly combines the dart of the trout with the
dash of the dolphin, to the rounded forehead and projecting muzzle of
which its own bullet head and bill exactly correspond. In its plunge,
if you watch it bathing, you may see it dip its breast just as much
under the water as a porpoise shows its back above. You can only
rightly describe the bird by the resemblances, and images of what it
seems to have changed from,--then adding the fantastic and beautiful
contrast of the unimaginable change. It is an owl that has been trained
by the Graces. It is a bat that loves the morning light. It is the
aërial reflection of a dolphin. It is the tender domestication of a
trout.
63. And yet be assured, as it cannot have been all these creatures, so
it has never, in truth, been any of them. The transformations believed
in by the mythologists are at least spiritually true; you cannot too
carefully trace or too accurately consider them. But the
transformations believed in by the anatomist are as yet proved true in
no single instance, and in no substance, spiritual or material; and I
cannot too often, or too earnestly, urge you not to waste your time in
guessing what animals may once have been, while you remain in nearly
total ignorance of what they are.
64. Do you even know distinctly from each other,--(for that is the real
naturalist's business; instead of confounding them with each
other),--do you know distinctly the five great species of this familiar
bird?--the swallow, the house-martin, the sand-martin, the swift, and
the Alpine swift?--or can you so much as answer the first question
which would suggest itself to any careful observer of the form of its
most familiar species,--yet which I do not find proposed, far less
answered, in any scientific book,--namely, why a swallow has a
swallow-tail?
It is true that the tail feathers in many birds appear to be
entirely,--even cumbrously, decorative; as in the peacock, and birds of
paradise. But I am confident that it is not so in the swallow, and that
the forked tail, so defined in form and strong in plume, has indeed
important functions in guiding the flight; yet notice how surrounded
one is on all sides with pitfalls for the theorists. The forked tail
reminds you at once of a fish's; and yet, the action of the two
creatures is wholly contrary. A fish lashes himself forward with his
tail, and steers with his fins; a swallow lashes himself forward with
his fins, and steers with his tail; partly, not necessarily, because in
the most dashing of the swallows, the swift, the fork of the tail is
the least developed. And I never watch the bird for a moment without
finding myself in some fresh puzzle out of which there is no clue in
the scientific books. I want to know, for instance, how the bird turns.
What does it do with one wing, what with the other? Fancy the pace that
has to be stopped; the force of bridle-hand put out in an instant.
Fancy how the wings must bend with the strain; what need there must be
for the perfect aid and work of every feather in them. There is a
problem for you, students of mechanics,--How does a swallow turn?
You shall see, at all events, to begin with, to-day, how it gets along.
65. I say you shall see; but indeed you have often seen, and felt,--at
least with your hands, if not with your shoulders,--when you chanced to
be holding the sheet of a sail.
I have said that I never got into scrapes by blaming people wrongly;
but I often do by praising them wrongly. I never praised, without
qualification, but one scientific book in my life (that I
remember)--this of Dr. Pettigrew's on the Wing;[12] and now I must
qualify my praise considerably, discovering, when I examined the book
farther, that the good doctor had described the motion of a bird as
resembling that of a kite, without ever inquiring what, in a bird,
represented that somewhat important part of a kite, the string. You
will, however, find the book full of important observations, and
illustrated by valuable drawings. But the point in question you must
settle for yourselves, and you easily may. Some of you perhaps, knew,
in your time, better than the doctor, how a kite stopped; but I do not
doubt that a great many of you also know, now, what is much more to the
purpose, how a ship gets along. I will take the simplest, the most
natural, the most beautiful of sails,--the lateen sail of the
Mediterranean.
[12] "On the Physiology of Wings." Transactions of the Royal
Society of Edinburgh. Vol. xxvi., Part ii. I cannot sufficiently
express either my wonder or regret at the petulance in which men
of science are continually tempted into immature publicity, by
their rivalship with each other. Page after page of this book,
which, slowly digested and taken counsel upon, might have been a
noble contribution to natural history, is occupied with dispute
utterly useless to the reader, on the question of the priority of
the author, by some months, to a French savant, in the statement
of a principle which neither has yet proved; while page after
page is rendered worse than useless to the reader by the author's
passionate endeavor to contradict the ideas of unquestionably
previous investigators. The problem of flight was, to all serious
purpose, solved by Borelli in 1680, and the following passage is
very notable as an example of the way in which the endeavor to
obscure the light of former ages too fatally dims and distorts
that by which modern men of science walk, themselves. "Borelli,
and all who have written since his time, are unanimous in
affirming that the horizontal transference of the body of the
bird is due to the perpendicular vibration of the wings, and to
the yielding of the posterior or flexible margins of the wings in
an upward direction, as the wings descend. I" (Dr. Pettigrew)
"am, however, disposed to attribute it to the fact (1st), that
_the wings_, both when elevated and depressed, _leap forwards_ in
curves, those curves uniting to form a continuous waved track;
(2d), _to the tendency which the body of the bird has to swing
forwards_, in a more or less horizontal direction, _when once set
in motion_; (3d), to the construction of the wings; they are
elastic helices or screws, which twist and untwist while they
vibrate, _and tend to bear upwards and onwards any weight
suspended from them_; (4th), _to the action of the air on the
under surfaces_ of the wings; (5th), _to the ever-varying power
with which the wings are urged_, this being greatest at the
beginning of the down-stroke, and least at the end of the up one;
(6th), _to the contraction of the voluntary muscles_ and elastic
ligaments, and to the effect produced by the various inclined
surfaces formed by the wings during their oscillations; (7th),
_to the weight of the bird_--weight itself, when acting upon
wings, becoming a propelling power, and so contributing to
horizontal motion."
I will collect these seven reasons for the forward motion, in the
gist of them, which I have marked by italics, that the reader may
better judge of their collective value. The bird is carried
forward, according to Dr. Pettigrew--
1. Because its wings leap forward.
2. Because its body has a tendency to swing forward.
3. Because its wings are screws so constructed as to screw
upwards and onwards any body suspended from them.
4. Because the air reacts on the under surfaces of the wings.
5. Because the wings are urged with ever-varying power.
6. Because the voluntary muscles contract.
7. Because the bird is heavy.
What must be the general conditions of modern science, when it is
possible for a man of great experimental knowledge and practical
ingenuity, to publish nonsense such as this, becoming, to all
intents and purposes, insane, in the passion of his endeavor to
overthrow the statements of his rival? Had he merely taken
patience to consult any elementary scholar in dynamics, he would
have been enabled to understand his own machines, and develop,
with credit to himself, what had been rightly judged or noticed
by others.
66. I draw it rudely in outline, as it would be set for a side-wind on
the boat you probably know best,--the boat of burden on the Lake of
Geneva (Fig. 3), not confusing the drawing by adding the mast, which,
you know, rakes a little, carrying the yard across it (_a_). Then, with
your permission, I will load my boat thus, with a few casks of Vevay
vintage--and, to keep them cool, we will put an awning over them, so
(_b_). Next, as we are classical scholars, instead of this rustic stern
of the boat, meant only to run easily on a flat shore, we will give it
an Attic [Greek: embolon] (_c_). (We have no business, indeed, yet, to
put an [Greek: embolon] on a boat of burden, but I hope some day to see
all our ships of war loaded with bread and wine, instead of artillery.)
Then I shade the entire form (_c_); and, lastly, reflect it in the
water (_d_)--and you have seen something like that before, besides a
boat, haven't you?
[Illustration: FIG. 3.]
There is the gist of the whole business for you, put in very small
space; with these only differences: in a boat, the air strikes the
sail; in a bird, the sail strikes the air: in a boat, the force is
lateral, and in a bird downwards; and it has its sail on both sides. I
shall leave you to follow out the mechanical problem for yourselves, as
far as the mere resolution of force is concerned. My business, as a
painter, is only with the exquisite organic weapon that deals with it.
67. Of which you are now to note farther, that a bird is required to
manage his wing so as to obtain two results with one blow:--he has to
keep himself up, as well as to get along.
But observe, he only requires to keep himself up _because_ he has to
get along. The buoyancy might have been given at once, if nature had
wanted _that_ only; she might have blown the feathers up with the hot
air of the breath, till the bird rose in air like a cork in water. But
it has to be, not a buoyant cork, but a buoyant _bullet_. And therefore
that it may have momentum for pace, it must have weight to carry; and
to carry that weight, the wings must deliver their blow with effective
vertical, as well as oblique, force.
Here, again, you may take the matter in brief sum. Whatever is the
ship's loss, is the bird's gain; whatever tendency the ship has to
leeway, is all given to the bird's support, so that every atom[13] of
force in the blow is of service.
[13] I don't know what word to use for an infinitesimal degree or
divided portion of force: one cannot properly speak of a force
being cut into pieces; but I can think of no other word than
atom.
68. Therefore you have to construct your organic weapon, so that this
absolutely and perfectly economized force may be distributed as the
bird chooses at any moment. That, if it wants to rise, it may be able
to strike vertically more than obliquely;--if the order is, go-ahead,
that it may put the oblique screw on. If it wants to stop in an
instant, that it may be able to throw its wings up full to the wind; if
it wants to hover, that it may be able to lay itself quietly on the
wind with its wings and tail, or, in calm air, to regulate their
vibration and expansion into tranquillity of gliding, or of pausing
power. Given the various proportions of weight and wing; the conditions
of possible increase of muscular force and quill-strength in proportion
to size; and the different objects and circumstances of flight,--you
have a series of exquisitely complex problems, and exquisitely perfect
solutions, which the life of the youngest among you cannot be long
enough to read through so much as once, and of which the future
infinitudes of human life, however granted or extended, never will be
fatigued in admiration.
69. I take the rude outline of sail in Fig. 3, and now considering it
as a jib of one of our own sailing vessels, slightly exaggerate the
loops at the edge, and draw curved lines from them to the opposite
point, Fig. 4; and I have a reptilian or dragon's wing, which would,
with some ramification of the supporting ribs, become a bat's or
moth's; that is to say, an extension of membrane between the ribs (as
in an umbrella), which will catch the wind, and flutter upon it, like a
leaf; but cannot strike it to any purpose. The flying squirrel drifts
like a falling leaf; the bat flits like a black rag torn at the edge.
To give power, we must have plumes that can strike, as with the flat of
a sword-blade; and to give _perfect_ power, these must be laid over
each other, so that each may support the one below it. I use the word
below advisedly: we have to strike _down_. The lowest feather is the
one that first meets the adverse force. It is the one to be supported.
[Illustration: FIG. 4.]
Now for the manner of the support. You must all know well the look of
the machicolated parapets in mediæval castles. You know they are
carried on rows of small projecting buttresses constructed so that,
though the uppermost stone, far-projecting, would break easily under
any shock, it is supported by the next below, and so on, down to the
wall. Now in this figure I am obliged to separate the feathers by white
spaces, to show you them distinctly. In reality they are set as close
to each other as can be, but putting them as close as I can, you get
_a_ or _b_, Fig. 5, for the rough section of the wing, thick towards
the bird's head, and curved like a sickle, so that in striking down it
catches the air, like a reaping-hook, and in rising up, it throws off
the air like a pent-house.
[Illustration: FIG. 5.]
70. The stroke would therefore be vigorous, and the recovery almost
effortless, were even the direction of both actually vertical. But
they are vertical only with relation to the bird's body. In space they
follow the forward flight, in a softly curved line; the downward
stroke being as effective as the bird chooses, the recovery scarcely
encounters resistance in the softly gliding ascent. Thus, in Fig. 5,
(I can only explain this to readers a little versed in the elements of
mechanics,) if B is the locus of the center of gravity of the bird,
moving in slow flight in the direction of the arrow, w is the locus of
the leading feather of its wing, and _a_ and _b_, roughly, the
successive positions of the wing in the down-stroke and recovery.
71. I say the down-stroke is as effective as the bird chooses; that is
to say, it can be given with exactly the quantity of impulse, and
exactly the quantity of supporting power, required at the moment. Thus,
when the bird wants to fly slowly, the wings are fluttered fast, giving
vertical blows; if it wants to pause absolutely in still air, (this
large birds cannot do, not being able to move their wings fast enough,)
the velocity becomes vibration, as in the humming-bird: but if there is
wind, any of the larger birds can lay themselves on it like a kite,
their own weight answering the purpose of the string,[14] while they
keep the wings and tail in an inclined plane, giving them as much
gliding ascent as counteracts the fall. They nearly all, however, use
some slightly gliding force at the same time; a single stroke of the
wing, with forward intent, seeming enough to enable them to glide on
for half a minute or more without stirring a plume. A circling eagle
floats an inconceivable time without visible stroke: (fancy the pretty
action of the inner wing, _backing_ air instead of water, which gives
exactly the breadth of circle he chooses). But for exhibition of the
complete art of flight, a swallow on rough water is the master of
masters. A sea-gull, with all its splendid power, generally has its
work cut out for it, and is visibly fighting; but the swallow plays
with wind and wave as a girl plays with her fan, and there are no words
to say how many things it does with its wings in any ten seconds, and
does consummately. The mystery of its dart remains always inexplicable
to me; no eye can trace the bending of bow that sends that living
arrow.
But the main structure of the noble weapon we may with little pains
understand.
[14] See App. p. 112, § 145.
72. In the sections _a_ and _b_ of Fig. 5, I have only represented the
quills of the outer part of the wing. The relation of these, and of the
inner quills, to the bird's body may be very simply shown.
Fig. 6 is a rude sketch, typically representing the wing of any bird,
but actually founded chiefly on the sea-gull's.
[Illustration: FIG. 6.]
It is broadly composed of two fans, A and B. The out-most fan, A, is
carried by the bird's hand; of which I rudely sketch the contour of the
bones at _a_. The innermost fan, B, is carried by the bird's forearm,
from wrist to elbow, _b_.
The strong humerus, _c_, corresponding to our arm from shoulder to
elbow, has command of the whole instrument. No feathers are attached to
this bone; but covering and protecting ones are set in the skin of it,
completely filling, when the active wing is open, the space between it
and the body. But the plumes of the two great fans, A and B, are set
into the bones; in Fig. 8, farther on, are shown the projecting knobs
on the main arm bone, set for the reception of the quills, which make
it look like the club of Hercules. The connection of the still more
powerful quills of the outer fan with the bones of the hand is quite
beyond all my poor anatomical perceptions, and, happily for me, also
beyond needs of artistic investigation.
73. The feathers of the fan A are called the primaries. Those of the
fan B, secondaries. Effective actions of flight, whether for support or
forward motion, are, I believe, all executed with the primaries, every
one of which may be briefly described as the strongest cimeter that can
be made of quill substance; flexible within limits, and elastic at its
edges--carried by an elastic central shaft--twisted like a windmill
sail--striking with the flat, and recovering with the edge.
The secondary feathers are more rounded at the ends, and frequently
notched; their curvature is reversed to that of the primaries; they are
arranged, when expanded, somewhat in the shape of a shallow cup, with
the hollow of it downwards, holding the air therefore, and aiding in
all the pause and buoyancy of flight, but little in the activity of it.
Essentially they are the brooding and covering feathers of the wing;
exquisitely beautiful--as far as I have yet seen, _most_ beautiful--in
the bird whose brooding is of most use to us; and which has become the
image of all tenderness. "How often would I have gathered thy children
... and ye would not."
74. Over these two chief masses of the plume are set others which
partly complete their power, partly adorn and protect them; but of
these I can take no notice at present. All that I want you to
understand is the action of the two main masses, as the wing is opened
and closed.
Fig. 7 roughly represents the upper surface of the main feathers of the
wing closed. The secondaries are folded over the primaries; and the
primaries shut up close, with their outer edges parallel, or nearly so.
Fig. 8 roughly shows the outline of the bones, in this position, of one
of the larger pigeons.[15]
[Illustration: FIG. 7.]
[Illustration: FIG. 8.]
[15] I find even this mere outline of anatomical structure so
interferes with the temper in which I wish my readers to think,
that I shall withdraw it in my complete edition.
75. Then Fig. 9 is (always sketched in the roughest way) the outer,
Fig. 10 the inner, surface of a sea-gull's wing in this position. Next,
Fig. 11 shows the tops of the four lowest feathers in Fig. 9, in mere
outline; A separate (pulled off, so that they can be set side by side),
B shut up close in the folded wing, C, opened in the spread wing.
[Illustration: FIG. 9.]
[Illustration: FIG. 10.]
[Illustration: FIG. 11.]
76. And now, if you will yourselves watch a few birds in flight, or
opening and closing their wings to prune them, you will soon know as
much as is needful for our art purposes; and, which is far more
desirable, feel how very little we know, to any purpose, of even the
familiar creatures that are our companions.
Even what we have seen to-day[16] is more than appears to have been
noticed by the most careful painters of the great schools; and you will
continually fancy that I am inconsistent with myself in pressing you to
learn, better than they, the anatomy of birds, while I violently and
constantly urge you to refuse the knowledge of the anatomy of men. But
you will find, as my system develops itself, that it is absolutely
consistent throughout. I don't mean, by telling you not to study human
anatomy, that you are not to know how many fingers and toes you have,
nor how you can grasp and walk with them; and, similarly, when you look
at a bird, I wish you to know how many claws and wing-feathers it has,
and how it grips and flies with them. Of the bones, in either, I shall
show you little; and of the muscles, nothing but what can be seen in
the living creature, nor, often, even so much.
[16] Large and somewhat carefully painted diagrams were shown at
the lecture, which I cannot engrave but for my complete edition.
77. And accordingly, when I now show you this sketch of my favorite
Holbein, and tell you that it is entirely disgraceful he should not
know what a wing was, better, I don't mean that it is disgraceful he
should not know the anatomy of it, but that he should never have looked
at it to see how the feathers lie.
Now Holbein paints men gloriously, but never looks at birds; Gibbons,
the wood-cutter, carves birds, but can't men;--of the two faults the
last is the worst; but the right is in looking at the whole of nature
in due comparison, and with universal candor and tenderness.