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:
“Novels so often provide an anodyne and not an antidote, glide one into torpid slumbers instead of rousing one with a burning brand.”
—Virginia Woolf (1882–1941)
“O, what a noble mind is here o’erthrown!
The courtier’s, soldier’s, scholar’s,eye, tongue, sword,
Th’ expectancy and rose of the fair state,
The glass of fashion and the mold of form,
Th’ observed of all observers, quite, quite down!”
—William Shakespeare (1564–1616)