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:
“Some of us who sit upon this platform have many a time been clamored down, and told that we had no right to speak, and that we were out of our place in public meetings; far be it from us, when women assemble, and a man has a thought in his soul, burning for utterance, to retaliate upon him.”
—Susan B. Anthony (1820–1906)
“The awaited scream rises,
the shattering
of glass and the cracking
of bone
a polar tumult as when
black ice booms....”
—Denise Levertov (b. 1923)