INDELIBLE MARKING INK, WITHOUT PREPARATION.—One drachm and a half of nitrate of silver (lunar caustic), one ounce of distilled water, half an ounce of strong mucilage of gum arabic, three-quarters of a drachm of liquid ammonia; mix the above in a clean glass bottle, cork tightly and keep in a dark place till dissolved, and ever afterwards. Directions for use:—Shake the bottle, then dip a clean quill pen in the ink, and write or draw what you require on the article; immediately hold it close to the fire (without scorching), or pass a hot iron over it, and it will become a deep and indelible black, indestructible by either time or acids of any description.—R. S. INCORRODIBLE AND INDELIBLE INKS.—Genuine asphaltum, one part; oil of turpentine, four parts; dissolve, and add lamp-black or black-lead to bring it to a proper consistence. _Or_—Asphaltum, one part; oil of turpentine, four parts; dissolve, and colour with printer’s ink, which any printer will sell by way of favour. These inks supply a cheap and excellent material for marking linen, &c. They are very permanent. They should be employed with stamps or types, or with the thin brass plates with letters cut therein. This method of marking is neater and easier than with the brush or pen. SYMPATHETIC INKS.—These are preparations used for writing on paper, the marks of which are invisible until acted upon by some re-agent. They are frequently employed in secret or playful correspondence. By heating the paper until it is nearly scorched, they may be rendered visible. 1. Sulphate of copper and sal-ammoniac, equal parts, dissolved in water—writes colourless, but turns yellow when heated. 2. Onion juice, like the last. 3. A weak infusion of galls—turns black when moistened with weak copperas water. 4. A weak solution of sulphate of iron—turns blue when moistened with a weak solution of prussiate of potash—black with infusion of galls. 5. The diluted solutions of nitrate of silver and terchloride of gold—darken when exposed to the sun-light. 6. Aqua-fortis, spirits of salts, oil of vitriol, common salt, or saltpetre, dissolved in a large quantity of water—turn yellow or brown when heated. 7. Solution of nitro-muriate of cobalt—turns green when heated, and disappears again on cooling. 8. Solution of acetate of cobalt, to which a little nitre has been added—becomes rose-coloured when heated, and disappears when cooling. STAINS OF WOOD.—The most effectual way of removing stains of most descriptions from wood, is to mix a quarter of an ounce of oil of vitriol with two ounces of water, and rub the stained surface with a cork dipped in this liquid, until the stains disappear: then wash with cold water. The colour of the wood is rendered pale for a time by this method, but it is brought up again by rubbing with furniture paste.