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Writing On Glass By The Rays Of The Sun


Dissolve chalk in aqua fortis, to the consistence of milk, and add to

that a strong solution of silver. Keep this liquor in a glass decanter

well stopped. Then cut out from a paper the letters you would have

appear, and paste the paper on the decanter, which you are to place in

the sun, in such a manner that its 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 turn black, and that

under the paper will remain white. You must observe not to move the

bottle during the time of the operation.



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