electroscope, which is fastened to its support by means of a silken
thread. A feather waved through the air is positively electrified,
while the air itself seems to be charged with negative electricity....
Two feathers rubbed together in the natural position are so
electrified that their lower surface is negative and the upper
positive.... These experiments and others still have been utilized to
study the vital relations of animals and the biological signification
of these phenomena. Most feathers stick together and remain so even
after being dried; if they then are waved through the air, the barbs
of the feather separate, owing to differences of electrification. No
bird needs to attend to its plumage at the end of a long flight, for
while the large feathers are positively electrified by friction
against the air, the white down has become negative, and so there is
attraction between it and the feathers. Another consequence of this
production of electricity during flight is that during winds, even the
most violent, the plumage does not become ruffled, but rests tightly
against the bird's body, for in this case the wing feathers, which
overlap, rub against each other and become electrified in contrary
senses. If the bird flies toward the ground, flapping its wings, it
compresses the air below them, and, supposing that the wing feathers
can bend aside, the experiments of Exner show that by the friction the
upper side of one feather and the lower side of that which is just
above are electrified oppositely, the more powerfully as the rubbing
is greater, which always causes them to resume the normal
position.--L'Electricien.

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