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Scale.—A graded system, by reference to which the degree, intensity, or quality of a sense perception may be estimated.

Shade.—Degree or gradation of defective luminosity in a color, often used vaguely from the fact that paleness, or high luminosity, combined with defective chroma, is confounded with high luminosity by itself. See Color, Hue, and Tint.

Spectrum.—In physics the continuous band of light showing the successive prismatic colors, or the isolated lines or bands of color, observed when the radiation from such a source as the sun or an ignited vapor in a gas flame is viewed after having been passed through a prism (prismatic spectrum) or reflected from a diffraction grating (diffraction or interference spectrum). See Rainbow.

Tint.—A variety of color; especially and properly, a luminous variety of low chroma; also, abstractly, the respect in which a color may be raised by more or less admixture of white, which at once increases the luminosity and diminishes the chroma.

Tone.—A sound having definiteness and continuity enough so that its pitch, force, and quality may be readily estimated by the ear. Musical sound opposed to noise. The prevailing effect of a color.

Ultramarine.—A beautiful natural blue pigment, obtained from the mineral lapis-lazuli.

VALUE.—In painting and the allied arts, relation of one object, part, or atmospheric plane of a picture to the others, with reference to light and shade, the idea of HUE being abstracted.

Vermillion.—The red sulphate of mercury.

Violet.—A general class of colors, of which the violet flower is a