speculum metal

American  

noun

1. any of several bronze alloys with a high tin content, often containing other materials, as silver, brass, lead, zinc, or arsenic, used for making mirrors and reflectors.

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speculum metal British  

noun

1. a white hard brittle corrosion-resistant alloy of copper (55–70 per cent) and tin with smaller amounts of other metals. It takes a high polish and is used for mirrors, lamp reflectors, ornamental ware, etc

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Etymology

Origin of speculum metal

First recorded in 1790–1800

Example Sentences

When completed, the disc of speculum metal was about six feet across and four inches thick.

From Great Astronomers by Ball, Robert S. (Robert Stawell), Sir

The same precipitate heated to a lower temperature is said to furnish a softer variety of rouge; at all events, it gives one more suitable for polishing speculum metal.

From On Laboratory Arts by Threlfall, Richard

For speculum metal when cold is excessively brittle, and were the casting permitted to cool like an ordinary copper or iron casting, the mirror would inevitably fly into pieces.

From Great Astronomers by Ball, Robert S. (Robert Stawell), Sir

L. M. Rutherfurd introduced into common use the reflection grating, finding that speculum metal was less trying than glass to the diamond point, upon the permanence of which so much depends.

From Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 4 "Diameter" to "Dinarchus" by Various

The gratings are solid slabs of polished speculum metal ruled with lines equidistant by a special machine of Prof. Rowland's invention.

From Scientific American Supplement, No. 365, December 30, 1882 by Various