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_--weigh