At the time of my experiments to determine the varying position of the center of pressure on an inclined plane moving in the air, I was unacquainted with the similar experimental work of Jo ssel ^[*] and of Kummer ^{[ ]} in the same field. Jo ssel, who appears to be the first experimenter on the subject, found for a square plane of length L that, as the angle between the plane and the current is diminished, the center of pressure approaches a point 1/5 L from the forward edge, and that its position for any angle a between the plane and the current may be represented by the formula

d being the distance of the center of pressure from the center of plane.

The method of experiment adopted by Kummer is essentially similar to the one pursued by me in the use of the Counterpoised Eccentric Plane. The object is to determine the position of the center of pressure corresponding to different angles of inclination of a plane to the current. The method pursued both by Kummer and myself has been the one which most naturally suggests itself to find the angle of inclination a of the plane corresponding to a series of fixed distances d of the center of pressure from the center of figure. Thus in the experiments, d has been the independent variable, while in the use of the results, a is in general the independent variable.

For a square...