LONDON. Royal Societyytfune 30.—A. Page and F.C. Johansen: On the flow of air behind an inclined flat plate of infinite span. The airflow behind a flat plate has been explored with a heated wire, used in conjunction with an Einthoven galvanometer. As the inclination of the plate is decreased from 90°, both the frequency and velocity with which individual vortices behind the plate pass downstream become greater; and the longitudinal spacing between successive vortices becomes smaller. Vorticity is shed at the same rate from the two edges of the plate; this rate slowly decreases with the inclination of the plate. Only a part of the vorticity generated at the edges passes downstream in the form of well-defined vortices.