Juniata sentinel and Republican. [volume] (Mifflintown, Juniata County, Pa.) 1873-1955, 1881-03-30
speed at Which W rngs are Driven.

The speed at which some wings are
driven is enormous. 1t is occasionally so
great es TO cause the pinionS to emit
drumming sound. To this source the
buzz of the fly, the drone of the bee, and
the boom of the beetle are TO be referred.
When a grouse, partridge, or pheasant
suddenly springs into the air, the sound
produced by the whirrIng of its wings
greatly resembles that produced by the
contact OF steel with the rapidly revolving
stone of the knife gIinder. 1t has been
estimated that the common fly moves its
wings $50 times per second, i. E., 19, $40
times per minute, and that the butterfly
moves its WINS nine times per second. or
$40 times per minute. These movements
represent an incredibly high speed even
at the roots of the wings, but the speed is
enormously increased at the tips of the
wings, from the fact that the tips rotate
upon the roots as centers. In rapIdIty,
and as has been already indicated, the
speed of the tips Of the wings increases In
proportion as the tips are removed from
the axes of rotation, and in proportion as
the wings are long. This is explained on
principle well understood IN mechanics
IL rod or wing hinged a. one point be
made to vibrate, the Tree end Of the rod or
wing always passes through very much
greater space IN given time than the part
nearer the root OF the wing. The progress
sive increase III the speed Of the wings, in
proportion as the wings become larger,
explains why the wings of bats and birds are
not driven at the exIrava salt speed OF insect
wings, and how the large and long wings
OF large bats and birds are driven more
leisuTely than small and short wings OF
small bats and birds. That the wing is
driven more slowly In proportion to its
length is proved by experiment, and by
observing the flight OF large and small
birds OF the same genus. Thus, large gulls
flap their wings much more slowly than
small gulls; the connguration and relative
size of the wings the body being The
same in both. 1nis is a hopeful feature
in the construction of flying machines, as
there can be no doubt tnat comparatively
very slow movements will suffice for drlv-
ing the long powerful wings required to
elevate and propel hying-nIachines. The
speed OF the wing is In part regulated 10y
the amplitude of the wing. Thus if the
wing be broad as well as long, the beats
are necessarily reduced in frequency. THIS
is especially true OF the heron, which is
one of the most picturesque and at the
same time one of the slowest-hyiug bird We
have. have timed the heron on several
occasions and find that in ordinary flight
its wings make exactly sixty up and sixty
down strokes, i. E., 12O beats per minute.
In the pterodactyl, the great extinct Sau
rian, the wing was enormously elongated,
and in this particular instance PROBABLY
from fifty TO sixty beats of the wing per
minute sufflced 1or flight. Fifty to sixty
pulsations OF the wing per minute do not
involve much wear and tear OF the WORK.
ing parts, and l am strongly of opinion
that artificial flight, if once achieved, will
become a comparatively safe means OF
locomotion as Tar as the machinery re-
Qulred is concerned.