Put as much gold in as small a quant.i.ty of aqua regia as will dissolve it, and dilute it with two or three times the quant.i.ty of distilled water.

Next dissolve, in a separate vessel, fine pewter in aqua regia, and when it is well impregnated, add an equal quant.i.ty of distilled water.

Write your characters with the first solution: let it dry in the shade. To make them visible, draw a pencil or sponge, dipped in the second solution, over the paper, and the characters will appear of a purple colour.

_Invisible Silver Ink._

Dissolve fine silver in aqua fortis; and after the dissolution, add some distilled water in the same manner as in the gold ink.

What is written with the above ink will remain invisible for three or four months, if kept from the air; but may be easily read in an hour, if exposed to the fire, air, or sun.

_Invisible Yellow Ink._

Steep marigold flowers seven or eight days in clear distilled vinegar.

Press the flowers and strain the liquor, which is to be kept in a bottle well corked. If you would have it still more clear, add, when you use it, some pure water.

To make the characters visible, which you write with this ink, pa.s.s a sponge over the paper, dipped in the following solution:

Take a quant.i.ty of flowers of pansy, or the common violet, bruise them in a mortar with water, strain the liquor in a cloth, and keep it in a bottle.

_Invisible Red Ink._

To the pure spirit of vitriol or nitre, add eight times as much water.

Use the above solution of violets to make visible the characters written with this ink.

_Invisible Green Ink._

Dissolve salt of tartar, clean and dry, in a sufficient quant.i.ty of river water. Use the violet solution to render it visible.

_Another Invisible Green Ink._

Dissolve zaffre, in powder, in aqua regia, for twenty-four hours. Pour the liquor off, and the same quant.i.ty of common water, and keep it in a bottle well corked.

This ink will not be visible till exposed to the fire or the sun; and will again be invisible when it becomes cold.

_Invisible Violet Ink._

Express the juice of lemons, and keep it in a bottle well corked. Use the violet infusion to make the writing visible.

_Invisible Grey Ink._

Mix alum with lemon-juice. The letters written with this ink will be invisible till dipped in water.

We now present our readers with a variety of amusing experiments, which may be performed by the foregoing inks; and they will, probably, suggest others equally amusing and useful.

_A Secret Correspondence by means of Invisible Ink._

A person wishing to carry on a correspondence with another, and who is fearful of having his letter opened, or intercepted, can adopt the following plan:

Write any unimportant matter with common ink, and let the lines be very wide apart: then between these lines write the communication you wish to make, with any of the above invisible inks you can most readily procure.

Your correspondent is to be previously apprized of the method of making the characters visible: and writing in common ink will serve to lull the suspicions of those who might intercept the letter, and who, not finding any thing important in it, will either forward or keep it.

In either case there can be no danger, as the writing will not be visible without the proper application.

_The Mysterious Writing._

Write on a piece of paper with common ink any question; then underneath it write the answer either in invisible silver ink, or the invisible green ink, made with zaffre and aqua regia, described in pages 24 and 25.

You give this paper to your friend, and tell him to place it against the wall, or on his dressing-table, keeping the door locked, that he may be sure no person has entered his room: he will next day find the answer written on it.

_The Restored Flowers._

Make a bouquet of artificial flowers; the leaves should be formed of parchment. Dip the roses in the red invisible ink, the jonquilles in the yellow, the pinks in the violet, and the leaves in the green ink.

They will all appear white; and you show them to the company, observing, that you will restore them to their natural colours, and desiring any person to fix any private mark on them he pleases, that he may be sure there is no deception. You then, unperceived by the company, dip them in the revivifying liquor, used to make the yellow ink visible, described in page 24, and, drawing them gently out, that the liquor may drop, and the flowers have time to acquire their colours, you present them to the company, who will see, with surprise, that they each appear in their natural colours.

_Winter changed to Spring._

Take a print that represents winter, and colour those parts which should appear green, with the second green invisible ink, described in page 25; observing, of course, the usual rules of perspective, by making the near parts deeper in colour than the others. The other objects must be painted in their natural colours. Then put the print into a frame with a gla.s.s, and cover the back with a paper that is pasted only at its extremities.

When this print is exposed to a moderate fire, or the warm sun, the foliage, which appeared covered with snow, will change to a pleasing green; and if a yellow tint be thrown on the lighter parts before the invisible ink is drawn over it, this green will be of different shades. When it is exposed to the cold, it will again resume its first appearance of winter.

_The Silver Tree._

Dissolve an ounce of fine silver in three ounces of strong aqua fortis, in a gla.s.s bottle. When the silver is dissolved; pour the aqua fortis into another gla.s.s vessel, (a decanter will be best,) with seven or eight ounces of mercury, to which add a quart of common water; to the whole add your dissolved silver, and let it remain untouched.

In a few days the mercury will appear covered with a number of little branches of a silver colour. This appearance will increase for a month or two, and will remain after the mercury is entirely dissolved.

_The Lead Tree._

A more modern invention, and an easier method by far than the above, is the following:

To a piece of zinc fasten a wire, crooked in the form of the worm of a still; let the other end of the worm be thrust through a cork. You then pour spring water into a phial or decanter, to which you add a small quant.i.ty of sugar of lead; thrust the zinc into the bottle, and with the cork at the end of the wire fasten it up. In a few days the tree will begin to grow, and produce a most beautiful effect.