7. Indestructible Red Ink may be made by dissolving one ounce of copal in seven ounces of oil of lavender, and adding thereto three ounces and a half of pure vermilion. If found too thick for the pen, add a little more oil of lavender.

8. Blue Ink. - Take sulphate of indigo (indigo dissolved in sulphuric acid, it may be had of the dyers), and dilute it with water till the desired tint is obtained. It is with this sulphate, very largely diluted, that the faint blue lines of ledgers and other books are ruled. If the ink were used strong, it would be necessary to add chalk to it, to neutralize the acid.

9. Yellow Ink. - Half a pound of French berries, boiled with a little alum in a quart of water, or vinegar and water.

10. Green and other coloured Inks. - A mixture of the above blue and yellow inks will make a green; a mixture of the red and yellow will make an orange; of the blue and red, a purple; of the black and yellow, a brown. Inks of all colours may, however, be very readily obtained by rubbing down with water any of the water-colours prepared in cakes, for artists; or by using a strong decoction of any of the ingredients used in dyeing, with a little alum and gum.

11. Marking Linen. - Mr. Haussman has given some compositions for marking pieces of cotton and linen, previous to their being bleached, which are capable of resisting every operation in the processes both of bleaching and dyeing, and consequently might be employed in marking linen for domestic purposes. One of these consists of asphaltum, dissolved m about four parts of oil of turpentine, and with this is to be mixed lamp-black or black-lead in fine powder, so as to make an ink of a proper consistence for printing with types. Another, - the blackish sulphate left after expelling oxygen gas from oxide of manganese with a moderate heat; being dissolved and filtered, the dark grey pasty oxide left on the filter is to be mixed with a very little of a solution of" gum tragacanth, and the cloth marked with this is to be dipped in a solution of potash or soda, mild or caustic, in about ten parts of water. The anacardium, or cashew nut, it is well known, yields an inflammable caustic liquor, which alone forms a very useful marking ink, as any thing written on linen or cotton with it is of a brown colour, which gradually grows blacker, and is very durable.

The ordinary marking ink sold in our shops is made in the following manner: - Take lunar caustic (nitrate of silver), 5 scruples; gum arabic, 5 scruples; sap-green, 1 scruple; water, 1 ounce; put these together in a small bottle, and the ink is formed. In using it, the linen is first wetted with the following mordant; - 1 ounce of soda to 2 ounces of water. The marking ink should not be used until the mordant has dried upon the linen.

12. Sympathetic, Invisible, or Secret Inks, are such as do not appear after they are written with, but which may be made visible at pleasure, by certain means used for that purpose. They are of considerable antiquity; for it appears that Ovid recommends the maidens of his days, who wished to correspond secretly with their lovers, to write with fresh milk, which when dried might be made visible by rubbing over it ashes or rust. Pliny, who was better informed than Ovid in such arts, though probably less inclined to practise them, recommended the milky juice of certain plants for the purpose; but the use of such things is superseded by the discoveries of modern chemists, who have introduced to our notice a great variety of secret inks, the best of which we find selected in the Oxford Cyclopaedia; they are as follow: - Dissolve some sugar of lead in water, and write with the solution. When dry, no writing will be visible. When you want to make it appear, wet the paper with a solution of alkaline sulphuret (liver of sulphur,) and the letters will immediately appear of a brown colour.

Even exposing the writing to the vapours of these solutions will render it apparent. - Write with a solution of gold in aqua-regia, and let the paper dry gently in the shade: nothing will appear; but draw a sponge over it, wetted with a solution of tin in aqua-regia, the writing will immediately appear of a purple colour. - Write with an infusion of galls, and when you wish the writing to appear, dip it into a solution of green vitriol; the letters will appear black. - Write with diluted sulphuric acid, and nothing will be visible. To render it so, hold it to the fire, and the letters will instantly appear black. - Juice of lemons or onions, a solution of sal ammoniac, green vitriol, etc. will answer the same purpose, though not so easily, nor with so little heat.

Green Sympathetic Ink

Dissolve cobalt in nitro-muriatic acid, and write with the solution. The letters will be invisible till held to the fire, when they will appear green, and will disappear completely again when removed into the cold. In this manner they may be made to appear and disappear at pleasure. A very pleasant experiment of this kind is to make a drawing representing a winter scene, in which the trees appear void of leaves, and to put the leaves on with this sympathetic ink; then upon holding the drawing near to the fire, the leaves will begin to appear in all the verdure of spring, and will very much surprise those who are not in the secret.

Blue Sympathetic Ink

Dissolve cobalt in nitric acid; precipitate the cobalt by potass; dissolve this precipitated oxide of cobalt in acetic acid, and add to the solution one-eighth of common salt. This will form a sympathetic ink, that, when cold, will be invisible, but will appear blue by heat.

13. Lithographic Ink. - As the art of lithography is treated of generally under its initial letter in this work, we shall in this place simply notice the autographic ink, suitable for transferring to stone the writings or drawings which have been executed on paper prepared for the purpose. This ink ought to be mellow, and somewhat thicker than that used for drawing or writing immediately on stone; so that when it is dry on the paper, it may be still sufficiently viscous to cause it to adhere to the stone by simple pressure. The following is the mode of preparing it: dry soap, 100 drachms; white wax, pure, 100 ditto; mutton suet, 30; shellac, 50; mastic 50; and lamp-black, (fine, from the combustion of resin,) 30 to 35 drachms. These are to be melted over a brisk fire in a metal pot over a chafing dish; first melt the soap and the suet, then add the shellac very gradually; next the soda, a little at a time, and after this the mastic, taking care to stir it from time to time with a wooden spatula; lastly the lamp-black, stirring it all the time.