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

In these instruments the lines are ruled upon a spherical surface of speculum metal, and mark the intersections of the surface by a system of parallel and equidistant planes, of which the middle member passes through the centre of the sphere.

From Project Gutenberg

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 Project Gutenberg

First: Water, of course, owing to its transparency, possesses not a perfectly reflective surface, like that of speculum metal, but a surface whose reflective power is dependent on the angle � 6.

From Project Gutenberg

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

From Project Gutenberg

A disc of a certain metallic composition, an alloy of copper and tin, known in consequence as speculum metal, had merely to be cast; and this had to be ground and polished upon one side only, whereas a lens has to be thus treated upon both its sides.

From Project Gutenberg