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:
“Private property is held sacred in all good governments, and particularly in our own. Yet shall the fear of invading it prevent a general from marching his army over a cornfield or burning a house which protects the enemy? A thousand other instances might be cited to show that laws must sometimes be silent when necessity speaks.”
—Andrew Jackson (1767–1845)
“Lay down, lay down the bigly bier,
Lat me the dead look on;
Wi’ cherry cheeks and ruby lips
She lay an’ smil’d on him.
O ae sheave o’ your bread, true-love,
An’ ae glass o’ your wine,
For I hae fasted for your sake
These fully day [is] nine.”
—Anna Gordon Brown (1747–1810)