A burning glass or burning lens is a large convex lens that can concentrate the sun's rays onto a small area, heating up the area and thus resulting in ignition of the exposed surface. Burning mirrors achieve a similar effect by using reflecting surfaces to focus the light. They were used in 18th-century chemical studies for burning materials in closed glass vessels where the products of combustion could be trapped for analysis. The burning glass was a useful contrivance in the days before electrical ignition was easily achieved.
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Famous quotes containing the words burning and/or glass:
“There are worse crimes than burning books. One of them is not reading them.”
—Joseph Brodsky (b. 1940)
“... this I conceive to be no time to prate of moral influences. Our men’s nerves require their accustomed narcotics and a glass of whiskey is a powerful friend in a sunstroke, and these poor fellows fall senseless on their heavy drills.”
—Clara Barton (1821–1912)