Soaring of Birds. To the Editor of the SCIENTIFIC AMERICAN: In the summer of 1872 I was visiting on the Warm Springs Reservation in eastern Oregon. The resi dences of the government employes, etc., were in a deep valley between table-lands through which the water-courses had cut deep canons. I climbed up on one of these tables, the edge of which was in most places perpendicular for ten, twenty, and more feet; and as I stood there in a strong breeze blowing against the face of the slope, a small hawk came gliding along eight or ten feet above the edge, and following the course of the edge; and he kept on until he was little more than a rod away from me. He seemed to be making no effort except a little balancing and turn ing in order to steer himself. The explanation seemed to me very simple; just there at the edge there was a strong, sharply-ascending current which enabled him to use wind and gravity against each other. In the autumn of that year I went to Foochow, China, and there I found the city frequented by a species of large bird which we call a kite. It seems to be half hawk, half buzzard in its build and habits. Its flight is heavy and awkward, its wings being too big for its pectoral muscles; and their tips are not pointed like a hawk's, but broad and square across. But it is a master of the art of soaring. There are in Foochow two hills which lie square across the path of the afternoon sea breeze. Here, toward the close of a breezy autumn afternoon, a dozen or a score of these kites will resort and have a genuine coasting game. The sides of the hills are quite steep, and of course there results a strong, sharp upward current at the top. The kites come to the top, and, starting from the eddy in the lee of the top, glide out into the up-rushing current, wings balancing up and down and head and tail turning and twisting, till they are in the heart of the upward current; and then they turn broadside to it and are borne upward and backward seventy-five or a hundred feet. Then they descend again into the eddy, and again steer themselves out into the uprushing current. Throughout it all there is very little flapping of the wings; and if the Ameri can boy could get his sled back to the top of the hill as easily as these kites get back into the uprushing current, no Chinaman could describe his coasting as: "Whish-sh-sh-sh--walkee backee mile!" One autumn day here in the interior I came to a stretch of waste land by the river covered with tall, dry grass and dwarf bamboos. A Chinaman had just set fire to it, and a strong column of smoke and hot air was ascending, when I saw one of these kites steer straight into that ascending column, and begin to circle round and round in it; and as he did so, he was steadily lifted upward as much as 150 or 200 feet. Then he went soaring off again. One cool, sunny day last spring, when the air was cool, but the sun very hot, I saw a kite steering for a group of buildings just in front of me, from the dark tile roofs of which cur rents of heated air were ascending. I supposed that the kite was coming to see if he could nab a spring chick; but when he reached the place he at once be gan circling round and round, sometimes from right to left, sometimes from left to right, at the same time drifting away before a nice breeze from the north; but as he did so he was gradually carried upward till he was at least 500 feet above the ground. Then he drew in his pinions somewhat, just as a hawk does in swoop ing, and, turning square against the breeze, glided away to the north with the speed of a race horse. Just west of where I now am is a long, steep slope of perhaps 2,000 feet. The lower half is in the lee of another mountain; but the upper half is fully ex posed to the southwest winds of the season. Recently when the wind was almost a gale, I saw a small hawk having a merry coast. The wind was gusty, and some times it would bear him up finely; and he would even take a shoot both upward against gravity, and outward against the wind. Again, the wind would suddenly fail him, and then he would flutter his wings much as a kingfisher does when poising over the water, till a fresh gust came to his help. I was much interested in the feats of Lilienthal. He had evidently mastered the kite's secret of the use of upward currents--the use of the upward current and gravity against each other--but alas! he did not have the kite's body, nor the kite's matchless skill in steer-Ing. J. E. WALKEK. Shaowu, Fukien, China, August 7, 1905.
Correspondence - October 14, 1905
This article was originally published with the title "Correspondence" in SA Supplements 60, 1554supp, 298 (October 1905)