Chronograph

Chronograph (time-recorder), a contrivance. used for the accurate measurement of periods of time. Thus in races Benson's chronograph is often employed; an instrument by which the beginning of the period and its close may be instantaneously and automatically registered upon a dial. A favourite type is a paper-covered cylinder revolving regularly, upon which the given moments are measured by the interruption of an electric current. The chronograph has been employed to mark the transit of a star in two different places, telegraphic communication enabling the two to be instantaneously compared. The velocity of projectiles may be measured by a chronograph composed of screens placed at varying distances from the gun's mouth, the passage through each screen breaking an electric current and marking itself.