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._