the world > physical sensation > sight and vision > optical instruments > lens > [noun] > burning glass (4)
A lens, by which the rays of the sun may be concentrated on an object, so as to burn it if combustible.
A lens for concentrating the rays of the sun so as to set light to combustible material. Cf. burning-glass, n.
A filter of darkened glass fitted to a sextant, telescope, etc., to reduce the intensity of the sun's light during observation. Now chiefly historical…