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or the cotton gin. This claim is founded upon the fact that in 1802 Mr. Wedgwood recorded an experiment in the Journal of the Royal Institution of the following nature. "A piece of paper, or other convenient material, was placed upon a frame and sponged over with a solution of nitrate of silver; it was then placed behind a painting on glass and the light traversing the painting produced a kind of copy upon the prepared paper, those parts in which the rays were least intercepted being of the darkest hues. Here, however, terminated the experiment; for although both Mr. Wedgwood and Sir Humphry Davey experimented carefully, for the purpose of endeavoring to fix the drawings thus obtained, yet the object could not be accomplished, and the whole ended in failure." This, by their own showing, was the earliest attempt of the English savans. But this much of the principle was known to the Alchemists at an early date-- although practically produced in another way--as the following experiment, to be found in old books, amply proves. "Dissolve chalk in aquafortis to the consistence of milk, and add to it a strong solution of silver; keep this liquor in a glass bottle well stopped; then cutting out from a piece of paper the letters you would have appear, paste it on the decanter, and lay it in the sun's rays in such a manner that the rays may pass through the spaces cut out of the paper and fall on the surface of the liquor the part of the glass through which the rays pass will be turned black, while that under the paper remains white; but particular care must be observed that the bottle be not moved during the operation."