The burning-glass concentrating the sun's rays on the red precipitate, being Priestley's original experiment.
He also gives descriptions of the camera obscura and of the burning-glass.
You can see how this is done with an ordinary magnifying glass, or burning-glass.
It was a magnificent day, the sun dazzled, and the bay sparkled like a burning-glass.
It was on that day that things began to come to a focus, a burning-glass of events that seemed to center on me.
A burning-glass had been fastened to the crucifix, and with that he had destroyed the idol.
Try the experiment of concentrating on a thermoscope, by means of a burning-glass, the moon's rays.
In China the burning-glass was widely used not very long ago.
Out of the saucepan shot a ball of fire like a flash of lightning; the next minute the burning-glass ceased to work.
The Duke's burning-glass was the instrument used to apply heat to the diamond.