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:
“What progress we are making. In the Middle Ages they would have burned me. Now they are content with burning my books.”
—Sigmund Freud (1856–1939)
“A glass of papaya juice
and back to work. My heart is in my
pocket, it is Poems by Pierre Reverdy.”
—Frank O’Hara (1926–1966)