3. When the water rises up to F, the piece at A will be visible; when it reaches G, both A and B will be visible; and when it comes up to H, all three pieces will be visible.
Artificial Earthquake and Volcano.
Grind an equal quantity of fresh iron filings with pure sulphur, till the whole be reduced to a fine powder. Be careful not to let any wet come near it. Then bury about thirty pounds of it a foot deep in the earth, and in about six or eight hours the ground will heave and swell, and shortly after send forth smoke and flames like a burning mountain. If the earth is raised in a conical shape, it will be no bad miniature resemblance of one of the burning mountains.
Artificial Illuminations.
A very pleasing exhibition may be made with very little trouble or expense, in the following manner: Provide a box, which you fit up with architectural designs cut out on pasteboard; prick small holes in those parts of the building where you wish the illuminations to appear, observing, that in proportion to the perspective, the holes are to be made smaller; and on the near objects the holes are to be made larger. Behind these designs thus perforated, you fix a lamp or candle, but in such a manner that the reflection of the light shall only shine through the holes; then placing a light of just sufficient brilliance to show the design of the buildings before it, and making a hole for the sight at the front end of the box, you will have a very tolerable representation of illuminated buildings.
The best way of throwing the light in front, is to place an oiled paper before it, which will cast a mellow gleam over the scenery, and not diminish the effect of the illumination. This can be very easily planned, both not to obstruct the sight, nor be seen to disadvantage. The lights behind the picture should be very strong; and if a magnifying glass were placed in the sight hole, it would tend greatly to increase the effect. The box must be covered in, leaving an aperture for the smoke of the lights to pass through.
The above exhibition can only be shown at candle-light; but there is another way, by fixing small pieces of gold on the building, instead of drilling the holes; which gives something like the appearance of illumination, but by no means equal to the foregoing experiment.
N.B. It would be an improvement, if paper of various colours, rendered transparent by oil, were placed between the lights behind and the aperture in the buildings, as they would then resemble lamps of different colours.
The Cameleon Spirit.
Put into a decanter volatile spirit, in which you have dissolved copper filings, and it will produce a fine blue. If the bottle be stopped, the colour will disappear; but when unstopped, it will return. This experiment may be often repeated.
Invisible Ink.
Put litharge of lead into very strong vinegar, and let it stand twenty-four hours. Strain it off, and let it remain till quite settled; then put the liquor in a bottle.
You next dissolve orpiment in quick lime water, by setting the water in the sun for two or three days, turning it five or six times a-day. Keep the bottle containing this liquor well corked, as the vapour is highly pernicious if received into the mouth.
Write what you wish with a pen dipped in the first liquor; and, to make it visible, expose it to the vapour of the second liquor. If you wish them to disappear again, draw a sponge or pencil, dipped in aqua fortis, or spirit of nitre, over the paper; and if you wish them to re-appear, let the paper be quite dry, and then pass the solution of orpiment over it.
Another.
Dissolve bismuth in nitrous acid. When the writing with this fluid is exposed to the vapour of liver of sulphur, it will become quite black.
Another.
Dissolve green vitriol and a little nitrous acid in common water. Write your characters with a new pen.
Next infuse small Aleppo galls, slightly bruised in water. In two or three days, pour the liquor off.
By drawing a pencil dipped in this second solution over the characters written with the first, they will appear a beautiful black.
Invisible Gold Ink.
Put as much gold in as small a quantity of aqua regia as will dissolve it, and dilute it with two or three times the quantity of distilled water.
Next dissolve, in a separate vessel, fine pewter in aqua regia, and when it is well impregnated, add an equal quantity 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, pass a sponge over the paper, dipped in the following solution:
Take a quantity 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 quantity 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 quantity 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.
