The flight of birds; the flapping cycle of the pigeon.

1. A new high-speed photographic method is described in detail. 2. Illustrations show the results obtained by the application of the technique to the study of bird flight. 3. A detailed account is given of the movements involved in the flapping cycle, with an attempt to indicate the principal muscles active at different parts of the cycle. 4. The basic conditions and limitations of the slow flight of the pigeon are discussed, and the expected differences between it and fast flight are indicated.