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

It is employed pure for numerous purposes, and is also mixed with other metals to form bell metal, speculum metal, for optical purposes, and German silver.

From The Mines and its Wonders by Kingston, William Henry Giles

A reflecting telescope of the present day would not be fitted with a mirror composed of that alloy known as speculum metal, whose composition I have already mentioned.

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

Third: Clear water takes no shadow, and that for two reasons; A perfect surface of speculum metal takes no shadow, � 8.

From Modern Painters Volume I (of V) by Ruskin, John