University of Virginia Library

Puzzle in Bird Soaring.

But a bird, which is also heavier than air, will remain suspended, in a calm, will even soar and move in a circle, without apparent movement of its wings. This is explained on the theory that there are generally vertical columns of air in circulation strong enough to sustain a bird, but much too weak to exert any lifting power on a flying machine, It is easy to understand how a

bird can remain suspended when the wind is in action, but its suspension in a seeming dead calm was a puzzle to scientists until Mr. Chanute advanced the proposition of vertical columns of air.