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An instrument for detecting the presence or movement of currents, as of electricity.

A small mirror for use in rhinoscopy.

Same as Gyroscope, 1.

An instrument that discloses objects in the dark or in a faint light. [Obs.] Pepys.

A seismometer.

An instrument for detecting small quantities of iron in any substance by means of a very delicate combination of magnetic needles.

A device for determining the refractive state of the eye by observing the movements of the retinal lights and shadows. -- Ski*as"co*py (#), Ski*as"co*py (#), n.

An optical instrument for forming and examining spectra (as that of solar light, or those produced by flames in which different substances are volatilized), so as to determine, from the position of the spectral lines, the composition of the substance.

Same as Sphygmograph.

A small instrument containing a minute particle of a radium compound mounted in front of a fluorescent screen and viewed with magnifying lenses. The tiny flashes produced by the continual bombardment of the screen by the a rays are thus rendered visible. -- Spin*thar`i*scop"ic (#), a.

A wet meter used to determine the breathing capacity of the lungs.

An optical instrument used in determining the position of the planes of light-vibration in sections of crystals.

An instrument with two lenses, by which an image of a single picture projected upon a screen of ground glass is made to present an appearance of relief, and may be viewed by several persons at once.

An optical instrument for giving to pictures the appearance of solid forms, as seen in nature. It combines in one, through a bending of the rays of light, two pictures, taken for the purpose from points of view a little way apart. It is furnished with two eyeglasses, and by refraction or reflection the pictures are sup…

To auscultate, or examine, with a stethoscope. M. W. Savage.

An apparatus for examining the interior of the mouth.

An optical toy similar to the phenakistoscope. See Phenakistoscope.

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.

An early form of antimated-picture machine, devised in 1889 by Otto Anschütz of Berlin, in which the chronophotographs were mounted upon the periphery of a rotating wheel.

of objects seen through the prisms are increased or diminished; -- called also prism telescope. Sir D. Brewster.