An able chemist, C. Wideman, has recently devised a curiosity in the way of engraving. It is a square piece of transparent glass in which absolutely nothing can be seen, even on the closest examination. If the glass be breathed upon, so as to cover its surface with moisture, a face like that shown in the [cut] makes its appearance. As soon as the moisture leaves the glass, the image disappears.
MAGIC PORTRAITS.
A piece of glass is obtained similar to that used for making mirrors. The glass may be transparent, tinned, or silvered; that makes no difference as to the final result. Then a small quantity of fluorspar is placed in a porcelain capsule and moistened with sufficient sulphuric acid to make the proper chemical reaction to write with. With this liquid and a quill pen the desired drawing or writing is executed on the previously well-cleaned glass. In about five minutes, or ten at the most, the glass is to be washed in common water and dried with a cloth. The plate will then be ready, and it will only be necessary to breathe upon it to see the figures that have thus been traced make their appearance.
A little practice will show the exact time necessary to leave the fluid lines on the glass. Too long a biting of the acid would be accompanied by so deep an engraving of the glass that the lines would always be perceptible, even on the dry glass.
A TRICK OPERA GLASS.
