AIRMEN AND SWALLOWS.
I hear indirectly from a great airman that the aeroplane has helped to settle one mystery, perhaps two, of birds' flight. In flying high over the Continent he came upon a flock of swallows marking time or hovering without progressing. They appeared to be just resting in the air without more labour than is entailed when a swimmer dabbles with his hands to keep his head above a still sea. This would probably be an impossible feat even to a swallow, whose bones are lightened by lungs or air-sacs distributed about the body, unless it were helped by a current of air. But a steady fronting wind would make the manoeuvre the easiest thing in the world. Men have slept standing ; and this would need much more effort than for a bird to keep equilibrium on the supporting air. My informant suggested that all manner of small birds might take a rest in this way on their long flights ; but hunger in their case is a worse enemy than weariness, and they pro- bably do their overseas journey in one dash. The airman's observation does something to corroborate our belief that some of the great sea birds, especially the albatross and lesser alba- tross, roost on the wing, maintaining equilibrium by reaching some air-stratum where the wind blows steadily in one direction.
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