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:
“Death is the mother of beauty, mystical,
Within whose burning bosom we devise
Our earthly mothers waiting, sleeplessly.”
—Wallace Stevens (1879–1955)
“It is difficult to read. The page is dark.
Yet he knows what it is that he expects.
The page is blank or a frame without a glass
Or a glass that is empty when he looks.”
—Wallace Stevens (1879–1955)