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:
“Thanks, thanks to thee, my worthy friend,
For the lesson thou hast taught!
Thus at the flaming forge of life
Our fortunes must be wrought;
Thus on its sounding anvil shaped
Each burning deed and thought!”
—Henry Wadsworth Longfellow (1809–1882)
“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)