crown glass

American  

noun

1. an optical glass of low dispersion and generally low index of refraction.

2. an old form of window glass formed by blowing a globe and whirling it into a disk.

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crown glass British  

noun

1. another name for optical crown

2. an old form of window glass made by blowing a globe and spinning it until it formed a flat disc

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Etymology

Origin of crown glass

First recorded in 1700–10

Example Sentences

Transparent media vary in their dispersive powers; for example, carbon disulphide has more than three times the dispersive power of crown glass.

From Project Gutenberg

The old staple trade of the making of crown glass, begun in 1777, lapsed some 70 years afterwards when the glass duty was abolished.

From Project Gutenberg

By studying the dispersion of colours in water, turpentine and crown glass Newton was led to suppose that dispersion is proportional to refraction.

From Project Gutenberg

Achromatic Object Glass. a, crown glass; b, flint glass.

From Project Gutenberg

A compound lens is needed, made up of a crown glass convex element, B, and a concave element, A, of flint glass.

From Project Gutenberg