Note 14 — Sound and Light.

Some time before the first announcement of the discovery of sun-painting, the following extract from Sir John Herschel’s Treatise on Light, in the Encyclopædia Metropolitana, appeared in a popular work entitled Parlour Magic: “Strain a piece of paper or linen upon a wooden frame, and sponge it over with a solution of nitrate of silver in water; place it behind a painting upon glass, or a stained window-pane, and the light, traversing the painting or figures, will produce a copy of it upon the prepared paper or linen; those parts in which the rays were least intercepted being the shadows of the picture.”