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The science of light; -- a general term sometimes employed when optics is restricted to light as a producing vision. Knight.

A combination of three optical lanterns for projecting objects on a screen in the colors of nature. The images of three partial photographs taken through color screens (red, green, and blue, respectively) are superimposed. Each image is given its own primary color, and these colors blend and reproduce the colors of th…

The doctrine or science of light, explaining its nature and phenomena; optics.

The degree to which a lens, mirror, or any optical instrument, magnifies; in the telescope, and usually in the microscope, the number of times it multiplies, or augments, the apparent diameter of an object; sometimes, in microscopes, the number of times it multiplies the apparent surface.

o the perspective plane. -- Principal section (Crystallog.), a plane passing through the optical axis of a crystal.

wo pairs of lobes, or elevations, on the dorsal side of the midbrain of most mammals; the optic lobes. The anterior pair are called the nates, and the posterior the testes.

See Range of cable, below. Range of accommodation (Optics), the distance between the near point and the far point of distinct vision, -- usually measured and designated by the strength of the lens which if added to the refracting media of the eye would cause the rays from the near point to appear as if they came from t…

ed by all crystals except those of the isometric system. A uniaxial crystal is said to be optically positive (like quartz), or optically negative (like calcite), or to have positive, or negative, double refraction, according as the optic axis is the axis of least or greatest elasticity for light; a biaxial crystal is s…

ce with another set in a different plane. -- Reticulated micrometer, a micrometer for an optical instrument, consisting of a reticule in the focus of an eyepiece. -- Reticulated work (Masonry), work constructed with diamond-shaped stones, or square stones placed diagonally.

e by which the back part of the globe of the eye is lined, and in which the fibers of the optic nerve terminate. See Eye.

Scioptic.

The optic capsule; the sclerotic coat of the eye. Owen.

prophetic vision. he was seized with a fit of second-sight. Addison. Nor less availed his optic sleight, And Scottish gift of second- sight. Trumbull.

of the injury have subsided. -- Secondary axis (Opt.), any line which passes through the optical center of a lens but not through the centers of curvature, or, in the case of a mirror, which passes through the center of curvature but not through the center of the mirror. -- Secondary battery. (Elec.) See under Batter…

d esp. at sea, for ascertaining the latitude and longitude. It is constructed on the same optical principle as Hadley's quadrant, but usually of metal, with a nicer graduation, telescopic sight, and its arc the sixth, and sometimes the third, part of a circle. See Quadrant.

Flat-nosed pliers, used by opticians for nipping off the edges of pieces of glass to make them round. Shank painter (Naut.), a short rope or chain which holds the shank of an anchor against the side of a vessel when it is secured for a voyage. -- To ride shank's mare, to go on foot; to walk.

ss on which is a picture or delineation to be exhibited by means of a magic lantern, stereopticon, or the like; a plate on which is an object to be examined with a microscope.

An optical instrument consisting of two lenses set in a light frame, and worn to assist sight, to obviate some defect in the organs of vision, or to shield the eyes from bright light.

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.

achnothera. -- Spider lines, filaments of a spider's web crossing the field of vision in optical instruments; -- used for determining the exact position of objects and making delicate measurements. Fine wires, silk fibers, or lines on glass similarly placed, are called spider lines. -- Spider mite. (Zoöl.) (a) Any on…