Flint glass effects a greater dispersion than crown glass nearly in the ratio of three to two.
The change amounts to the addition of a double convex lens of crown glass having a radius of a third of an inch.
Thus, the spectrum formed by flint glass is longer than that formed by crown glass, for the same deviation.
These bull's eyes were the centers or waste from large discs of crown glass after all the big pieces possible had been cut away.
The achromatic lens consists of a double convex lens of crown glass combined with a plano-concave lens of flint glass.
crown glass comes next, or window glass, formed in large circular plates or discs.
The focal length of double convex lenses of crown glass is about the same as the radius of curvature of either surface.
The pot is an inverted truncated cone, like a crown glass pot.
These works, in which plate and every kind of crown glass is made, are situated at West Bromwich.
Thus the dispersive power of flint glass and balsam are about equal, while that of crown glass is considerably less.