| flint glass | <chemistry> A soft, heavy, brilliant glass, consisting essentially of a silicate of lead and potassium. It is used for tableware, and for optical instruments, as prisms, its density giving a high degree of dispersive power; so called, because formerly the silica was obtained from pulverized flints. Synonym: crystal glass. Cf. Glass. The concave or diverging half on an achromatic lens is usually made of flint glass. Source: Websters Dictionary (01 Mar 1998) |
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| lady's looking-glass | <botany> See Venus's looking-glass, under Venus. Source: Websters Dictionary (01 Mar 1998) |
| focusing glass | <microscopy> A hand magnifier, used at the focal plane of a camera, usually with the ground glass removed. Its purpose is to examine the image for critical focus. It is, as a rule, a low-power magnifier so mounted that it is in focus when supported on a piece of clear glass at the focal plane of the cam- era, for studying the image. It operates equally well on the aerial image. (05 Aug 1998) |