glass. 1

A hard, brittle, homogeneous, transparent substance, made by melting sand and consisting e entially of a metallic silicate with silicic acid, with soda or potash, etc. 2. A lens, mirror, or other implement having its e ential parts made of that material. 3. In the pi., gla es, spectacles; lenses, prisms, or plane, usually oval sheets of g. mounted to be worn before the eyes for the correction of visual defects or for purposes of protection, binocular g. An optical instrument for use with both eyes simultaneously, burning g. A large convex lens used to produce an intense heat by converging the sun's rays to a focus. cover g. A thin sheet of g. for mounting or covering microscopical specimen on a slide, crown g. A g. containing the metals pota ium and calcium, used in the manufacture of lenses, eye g'es. G'es (2nd def.) so mounted as to rest on the nose without other support, but usually grasping it by a spring, flint g. A g. containing varying amounts of lead. It has a high index of refraction and is used in the manufacture of lenses, etc. focusing g. A simple microscope for determining when the image in a photographic camera is sharply focused on the ground gla . Franklin g. See under Franklin, g. wool. G. obtained in the form of elastic fibers by reeling off molten g. It is used in filtering, and has been employed as a drainage material for wounds, magnifying g. A convex g. used for magnifying objects; a simple microscope. periscopic g'es. Positive or negative menisci or lenses having one concave and one convex surface of different curvature so as to diminish spherical aberration, soluble g. See water g. spun g. See g. wool, water g. An aqueous solution of sodium silicate. [Mid. Eng., glas, gles, from Ang.- Sax., glaes.