1 See: Proceedings of the Royal Society of Medicine, Section of Orthopaedics; Presidential Address “The Physiology of Muscular Action,” by A. S. Blundell Bankart, M.Ch., Oct. 6th, 1925; from £ beginning “It isi now known that the skeletal muscles exhibit two kinds of activity.”

2 Reprinted by this Society 1910 Aeronautical Classics No. 2. The importance of Wenham's evidence justifies a longer quotation: “One of the first birds in the scale of flying magnitude is the pelican. It is seen in the streams and estuaries of warm climates, fish being its only food. On the Nile, after the inundation, it arrives in flocks' of many hundreds together, having migrated from long distances. A specimen shot was found to weigh twenty-one pounds, and measured ten feet across the wings, from end to end. The pelican rises with much difficulty, but, once on the wing, appears to fly with very little exertion, notwithstanding its great weight. Their- mode of progress is peculiar and graceful. They fly after a leader, in one, single train. As he rises or descends, so his followers do the same in succession, imitating his movements precisely. At a distance this gives them the appearance of a long undulating ribbon, glistening under the cloudless sun of an oriental sky. During their flight they make about seventy strokes per minute with their wings. This uncouth-looking bird is somewhat whimsical in its habits. Groups of them may be seen far above the earth, at a distance from the river side, soaring apparently for their own pleasure. With outstretched and motionless wings, they float serenely, high in the. atmosphere, for more than an hour together, traversing the same locality in circling movements. With head thrown back, and enormous bills resting on their breasts, they almost seem asleep. A few easy strokes of their wings each minute, as their momentum or velocity diminishes, serves to keep them sustained at the same level. The effort required is obviously slight and not confirmatory of the excessive amount of power said to be requisite for maintaining the flight of a bird of this weight and size. The pelican displays no symptom of being endowed with great strength, for when only1 slightly wounded it is easily1 captured, not having adequate power for effective resistance, but heavily flapping the huge wings, that should, as some imagine, give a stroke equal in vigour to the kick of a horse. During a calm evening, flocks of spoon bills take their flight directly up the river's course; as if linked together in unison, and moved by the same impulse, they alter not their relative positions, but at less than fifteen inches above the water's surface, they speed swiftly by with ease and grace inimitable, a living sheet of spotless white. Let one circumstance be remarked—though they have fleeted past at a rate of nearly thirty miles an hour, so little do they disturb the element in which they move that not a ripple of the placid bosom of the river, which they almost touch, has marked their track.”

3 Journal of this Society, October, 1930, and December, 1931.

4 “ Le Vol des Oiseaux,” Marey, Paris, 1890, p. 23.

5 Certain observations of the relation between the weight of the wing and the total weight of the bird, are recorded by the late M. Jose1 Weirs in a paper entitled “ Rapports des poids aux surfaces ” in L'Aerophile, 15 Jan., 1910.

6 “ An Approach to Winged Flight,” Dolphin Press, Brighton, 1928.

7 The part, which in the artificial wing I call the blade, is the part composed, in the natural wing, of all the primary and some of the secondary feathers. In so calling it, I adopt the metaphor implied in the ornithologist's term “ -remiger ” translating it back into English. I learn from Marey (page 71) that the part composed of the primary feathers is, in French, called “ le fouet,” by which I understand “ the lash.”