a conical rifle bullet to
the entire front of the body; and, indeed, the bird moves more like a
bullet than an arrow--dependent on a certain impetus of weight rather
than on sharp penetration of the air. I say dependent on, but I have
not yet been able to trace distinct relation between the shapes of
birds and their powers of flight. I suppose the form of the body is
first determined by the general habits and food, and that nature can
make any form she chooses volatile; only one point I think is always
notable, that a complete master of the art of flight must be
short-necked, so that he turns altogether, if he turns at all. You
don't expect a swallow to look round a corner before he goes round it;
he must take his chance. The main point is that he may be able to stop
himself, and turn, in a moment.

47. The stopping, on any terms, is difficult enough to understand; nor
less so, the original gaining of the pace. We always think of flight as
if the main difficulty of it were only in keeping up in the air;--but
the buoyancy is conceivable enough, the far more wonderful matter is
the getting along. You find it hard work to row yourself at anything
like speed, though your impulse-stroke is given in a heavy element, and
your return-stroke in a light one. But both in birds and fishes, the
impelling stroke and its return are in the same element; and if, for
the bird, that medium yields easily to its impulses, it secedes as
easily from the blow that gives it. And if you think what an effort you
make to leap six feet, with the earth for a fulcrum, the dart either of
a trout or a swallow, with no fulcrum but the water and air they
penetrate, will seem to you, I think, greatly marvelous. Yet of the
mode in which it is accomplished you will as yet find no undisputed
account in any book on natural history, and scarcely, as far as I know,
definite notice even of the rate of flight. What do you suppose it is?
We are apt to think of the migration of a swallow, as we should
ourselves of a serious journey. How long, do you think, it would take
him, if he flew uninterruptedly, to get from here to Africa?

48. Michelet gives the rate of his flight (at full speed, of course,)
as eighty leagues an hour. I find no more sound authority; but do not
doubt his approximate accuracy;[10] still how curious and how
provoking it is that neither White of Selborne, Bewick, Yarrell, nor
Gould, says a word about this, one should have thought the most
int