burning glass

a converging lens used to produce heat or ignite substances by focusing the sun's rays.

Also called sunglass.

Origin of burning glass

First recorded in 1560–70

I took the precaution, however, to put the burning-glass into my pocket, lest we should want fire.

The Coral Island |R. M. Ballantyne
In the material uses of the burning-glass we have a parallel for the value of an intellectual or religious symbol.

A Handbook to the Works of Browning (6th ed.) |Mrs. Sutherland Orr
“No sign of Mejia yet,” observed Carmen, as he lighted his cigar with a burning-glass.

Mr. Fortescue |William Westall
Try with the burning-glass to concentrate heat from hot iron, from common flame, from boiling water.

An Introduction to the History of Science |Walter Libby

With the first mist of indifference the wise teacher will drop the burning-glass.

Sunday-School Success |Amos R. Wells

burning glass

a convex lens for concentrating the sun's rays into a small area to produce heat or fire