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:
“And if any mischief follow, then thou shalt give life for life, eye for eye, tooth for tooth, hand for hand, foot for foot, burning for burning, wound for wound, stripe for stripe.”
—Bible: Hebrew Exodus 21:23.
“We are little airy creatures,
All of different voice and features:
One of us in glass is set,
One of us you’ll find in jet,
T’other you may see in tin,
And the fourth a box within;
If the fifth you should pursue,
It can never fly from you.”
—Jonathan Swift (1667–1745)