The suggestion has been put forward by Dr. A. P. Thurston that the characteristics of a wing can be considerably improved by adding self-starting rotors at or near the wing tips. It is claimed that by placing these on each wing near the leading edge improvements analogous to those of a slotted wing tip can be obtained together with slow landing characteristics. Previous experiments (1) have shown that rotors can give about the same degree of lateral stability as tip slots. The primary object of these experiments was to test the second assertion, and the criterion by which this should be judged was that the gliding angle should be as steep as possible for a given rate of descent.