Emily Dickinson Lexicon

RE-FRAC'TION, n.

The deviation of a moving body, chiefly rays of light, from a direct course. This as occasioned by the different densities of the mediums through which light passes. Refraction out of a rarer medium into a denser, is made toward the perpendicular. – Newton. Refraction may be caused by a body's falling obliquely out of one medium into another. – Encyc. Refraction double, the separation of a ray of light into two separate parts, by passing through certain transparent mediums, as the Iceland crystal. All crystals, except those whose primitive form is either a cube or a regular octahedron, exhibit double refraction.