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.
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.