dense flint

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• industrial glass — Introduction       solid material that is normally lustrous and transparent in appearance and that shows great durability under exposure to the natural elements. These three properties lustre, transparency, and durability make glass a favoured… …   Universalium

• Abbe number — An Abbe diagram plots the Abbe number against refractive index for a range of different glasses (red dots). Glasses are classified using the Schott Glass letter number code to reflect their composition and position on the diagram …   Wikipedia

• eyeglasses — Lenses set in frames to wear in front of the eyes to aid vision or correct vision defects (see ophthalmology, optometry). Their use for farsightedness and nearsightedness has been known since the late Middle Ages. In 1784 Benjamin Franklin… …   Universalium

• Verdet constant — The Verdet constant is an optical constant that describes the strength of the Faraday effect for a particular material.The Verdet constant for most materials is extremely small and is wavelength dependent. It is strongest in substances containing …   Wikipedia

• refractive index — Optics. See index of refraction. [1830 40] * * * ▪ physics also called  Index Of Refraction,         measure of the bending of a ray of light when passing from one medium into another. If i is the angle of incidence of a ray in vacuum (angle… …   Universalium

• GEOGRAPHICAL SURVEY — Names The name Ereẓ Israel (the Land of Israel) designates the land which, according to the Bible was promised as an inheritance to the Israelite tribes. In the course of time it came to be regarded first by the Jews and then also by the… …   Encyclopedia of Judaism

• hand tool — any tool or implement designed for manual operation. * * * Introduction  any of the implements used by craftsmen in manual operations, such as chopping, chiseling, sawing, filing, or forging. Complementary tools, often needed as auxiliaries to… …   Universalium

• native American — native American, adj. a person born in the United States. [1835 45, Amer.] * * * ▪ indigenous peoples of Canada and United States Introduction also called  American Indian,  Amerindian,  Amerind,  Indian,  Aboriginal American,  or  First Nation… …   Universalium

• Native American — Indian (def. 1). Usage. See Indian, Eskimo. * * * ▪ indigenous peoples of Canada and United States Introduction also called  American Indian,  Amerindian,  Amerind,  Indian,  Aboriginal A …   Universalium

• VERRE — Les verres constituent un ensemble extrêmement varié de produits dont les propriétés sont innombrables. Celles ci dépendent fortement des traitements subis, thermiques notamment. Leur mise au point résulte aujourd’hui des progrès des… …   Encyclopédie Universelle

• pre-Columbian civilizations — Introduction       the aboriginal American Indian (Mesoamerican Indian) cultures that evolved in Meso America (part of Mexico and Central America) and the Andean region (western South America) prior to Spanish exploration and conquest in the 16th …   Universalium