11 ([Return])
Incidentally suggestive sentences occur in the history of Selborne, but its author never comes to the point, in this case.
12 ([Return])
"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.
13 ([Return])
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.
14 ([Return])
See App. p. 112, § 145.