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:
“A certain minor light may still
Leap incandescent
Out of kitchen table or chair
As if a celestial burning took
Possession of the most obtuse objects now and then—”
—Sylvia Plath (1932–1963)
“You doubt we read the stars on high,
Nathless we read your fortunes true;
The stars may hide in the upper sky,
But without glass we fathom you.”
—Ralph Waldo Emerson (1803–1882)