TABLE OF CONTENTS The Component Pressure Recorder (or Component Recorder), plate VII, may be compared to a balance which rocks on a knife-edge bearing, in the ordinary way, but which also oscillates horizontally about a vertical axis. With respect to its vertical oscillations about the knife-edge bearing, it is a true balance, whose arms, each one meter long, are in delicate equilibrium, and I will call this part of the instrument distinctively the balance.
If an actual working aerodrome model with its motor be not used upon the outer arm (outer, that is, as reckoned from the center of the turn-table), a plane of given weight (the wind-plane ) is clamped there, so as to make any desired angle of inclination with the horizon. The horizontal oscillation about the vertical axis provides for the measurement of the horizontal component of pressure on this plane; the vertical oscillation on the knife-edge provides for measuring the vertical component. The horizontal pressure is measured by the extension of a spring fastened to an arm moving around the axis with the horizontal oscillation of the balance, and to the surrounding fixed frame. The vertical component of pressure is measured only when it is equal to the weight of the plane i. e., by the fact that the plane is actually just lifted by the wind of rotation, or, in the technical term previously used, when it soars. The requisite registration of this fact is automatically accomplished by making an electric contact.
