An Etymological Dictionary of Astronomy and Astrophysics

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فرهنگ ریشه‌شناختی اخترشناسی-اخترفیزیک

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crown glass
  کرون، شیشه‌ی ِ ~  
crown, šiše-ye ~ (#)
Fr.: crown, crown-glass  

An optical, alkali-lime glass which is harder than → flint glass, and has a lower → index of refraction and lower → dispersion. It is used in the production of → compound lenses.

See also: Such named because of the crown-like shape given to the blank after the process of blowing the glass; M.E. coroune, from O.Fr. corone, from L. corona “crown,” originally “wreath, garland;” cf. Gk. korone “anything curved, kind of crown;” → glass.