TACHISTOSCOPE
Ta*chis"to*scope, n. [Gr. , superl. of swift + -scope.] (Physiol.)
Defn: An apparatus for exposing briefly to view a screen bearing letters or figures. It is used in studying the range of attention, or the power of distinguishing separate objects in a single impression.
TACHOGRAPH
Tach"o*graph, n. [Gr. speed + -graph.]
Defn: A recording or registering tachometer; also, its autographic record.
TACHOMETER
Ta*chom"e*ter, n. Etym: [Gr. -meter: cf. F. tachomètre.]
Defn: An instrument for measuring the velocity, or indicating changes in the velocity, of a moving body or substance. Specifically: — (a) An instrument for measuring the velocity of running water in a river or canal, consisting of a wheel with inclined vanes, which is turned by the current. The rotations of the wheel are recorded by clockwork. (b) An instrument for showing at any moment the speed of a revolving shaft, consisting of a delicate revolving conical pendulum which is driven by the shaft, and the action of which by change of speed moves a pointer which indicates the speed on a graduated dial. (c) (Physiol.) An instrument for measuring the velocity of the blood; a hæmatachometer.
TACHOMETRY
Ta*chom"e*try, n.
Defn: Measurement by a tachometer; the science or use of tachometers.
TACHYDIDAXY
Tach"y*di*dax`y, n. Etym: [Gr.
Defn: A short or rapid method of instructing. [R.]