The Changeable Picture.

Paint upon thin paper, in a slight manner, and with very light colours, any subject at pleasure, but disposed in such a manner, that by painting the paper stronger on the other side, it may be entirely disguised. Then cover the last side with a piece of white paper, to conceal the second subject, and inclose the whole in a frame, and even between two pieces of glass.

If you hold this picture between you and the light, and look through it, a subject will be seen very different from that which it exhibits when looked at in the usual manner.

Golden Ink.

As writing, before the invention of printing, was the only method of transmitting to posterity the works and discoveries of celebrated men, it became in the fourteenth and fifteenth centuries, an art much cultivated, and in which many persons excelled. The manuscripts of those periods contain writing, the neatness and regularity of which are astonishing. Transcribers were even acquainted with a method of ornamenting the initial letters with gold, which they applied in such a manner as to preserve all its splendour.

Writing, by the invention of printing, having become of less importance, soon degenerated, and the secret of applying gold to paper and parchment, like many other arts, was at length lost. The Benedictines, however, re-discovered this secret, and specimens of the process, and parchment containing writing in gold letters, as brilliant as those so much admired in the ancient manuscripts, have been seen at the Abbey Saint Germain des Pres, at Paris. This process may be exceedingly useful, and may furnish hints for improving some of the other arts, which are all connected, and mutually tend to promote each other.

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Process translated from the German.

Take a certain quantity of gum arabic, the whitest is the best; and, having reduced it to an impalpable powder in a brass mortar, dissolve it in strong brandy, and add to it a little common water, to render it more liquid. Provide some gold in a shell, which must be detached, in order to reduce it to a powder. When this is done, moisten it with the gummy solution, and stir the whole with your finger, or with a small hairbrush; then leave it at rest for a night, that all the gold may be better dissolved. If the composition becomes dry during the night, it must be diluted with more gum water, in which a little saffron has been infused; but care must be taken that the gold solution be sufficiently liquid to be employed with the pen. When the writing is dry, polish it with a dog's tooth.

Another Process.

Reduce gum ammoniac to powder, and dissolve it in water in which gum arabic has been previously dissolved, and to which a little garlic juice has been added. This water will not dissolve the gum so as to form a transparent fluid; for the result will be a milky liquor. With this liquor you must form your letters or ornaments, on paper or vellum, by means of a pen or hairbrush; then suffer them to dry, and afterwards breathe on them for some time, till they become somewhat moist, and immediately apply a few bits of gold leaf cut to the size of the letters; press the gold leaf gently with a ball of cotton, or bit of soft leather, and when the whole is dry, take a soft brush and draw it gently over the letters, to remove the superfluous gilding. The parts which you wish to polish and render brilliant, may then be burnish'd with a dog's tooth.

White Ink, to write on Black Paper.

Take egg-shells, and having carefully washed them, remove the internal pellicle, and grind them on a piece

of porphyry. Then put the powder into a small vessel filled with pure water, and when it has settled at the bottom, decant the water, and dry the powder in the sun. This powder must be preserved in a bottle. When you are desirous of using it, put a small quantity of very pure gum ammoniac into distilled vinegar, and leave it to dissolve during the night; next morning the solution will appear exceedingly white, and if you then strain it through a piece of linen cloth, and add to it the powder of egg-shells, in sufficient quantity, you will obtain a very white ink.

Red Ink.

Boil four ounces of Brazil wood in two pints of water, for a quarter of an hour, and having added a little alum, gum arabic, and sugar-candy, suffer the whole to boil for a quarter of an hour longer. This ink may be preserved a long time, and the older it grows, it will still become redder.

Blue Ink.

Blue ink may be obtained by diluting indigo and ceruse in gum water.

Yellow Ink.

Take saffron and yellow berries (graine d'Avignon,) or gamboge, and dilute them as before, in gum water.

Green Ink.

This ink is made by boiling sap-green in water, in which a little rock alum has been dissolved.

Ink of different Colours, made from the Juice of Violets.

Dip a camel's hair brush in any acid, such as diluted spirit of vitriol, and draw it over a part of the paper. When the liquor is dry, write on it with a pen dipped

in violet juice, and the writing will immediately appear of a beautiful red colour.

If a camel's hair brush, dipped in an alkaline solution, such as that of salt of wormwood in water, be drawn over the other part of the paper, by writing on it when dry with juice of violets, you will obtain characters of a beautiful green colour.

If you write with the juice of violets, and draw a brush dipped in spirit of hartshorn, or a solution of salt of wormwood dissolved in water, over another, you will have red and green writing..

By exposing this writing to the fire, it will become yellow.

If you write on paper with an acid, such as lemonjuice (which is as proper for this purpose as any other) and then suffer it to dry, the writing will be invisible till brought near the fire, when it will become as black as ink. The juice of onions produces the same effect.

The older writing of this kind is the more beautiful the colour becomes; and in like manner the longer the spirit of vitriol, or solution of salt of wormwood, &c. has been left to dissolve, before they are used to write with, the brighter will be the colours.

Tracing Ink.

This name is given to a kind of ink employed for tracing out figures, and other subjects, intended to be engraved, as by means of pressure it may be transferred from paper, and fixed on the white wax with which engravers cover their plates.

To compose this ink take gunpowder finely pounded, and add to it an equal quantity of printer's black; then put the whole into water with a little Roman vitriol, and stir the mixture, giving it such a consistence that it may be neither too thin nor too thick. Before the ink is used, shake it well, because the black is apt to deposit itself at the bottom of the vessel.

China, or Indian Ink.

China ink, which is employed for small drawings and plans, may easily be made by the following process. Take the kernels of the stones of apricots, and burn them in such a manner as to reduce them to powder, but without producing flame; which may be done by wrapping up a small packet of them in a cabbage leaf, and tying round it a bit of iron wire. Put this packet into an oven, heated to the same degree as that required for baking bread, and the kernels will be reduced to a sort of charcoal, with which an ink may be made similar to that brought from China.

Pound this charcoal in a mortar, and reduce it to an impalpable powder, which must be sifted through a fine sieve; then form a pretty thick solution of gum arabic in water, and, having mixed it with the powder, grind the whole on a stone, in the same manner as colourmen grind their colours. Nothing is then necessary, but to put the paste into some small moulds, formed of cards, and rubbed over with white wax, to prevent it adhering to them.

In regard to the smell of the China ink, it arises. from a little musk which the Chinese add to the gum water, and may easily be imitated. The figures seen on the sticks of China ink, are the particular marks of the manufacturers, who, as in all other countries, are desirous of distinguishing whatever comes from their hands.

Dr. Lewis thinks, from the information of Father du Halde, that China ink is composed of nothing but lamp-black and animal glue. Having boiled a stick of China ink in several portions of water, in order to extract all the soluble parts, and having filtered the different liquors, which he evaporated in a stone vessel, he found that the liquors had the same odour as glue, and that they left, after evaporation, a pretty considerable quantity of a tenacious substance, which seemed to differ in nothing from common glue.