The following will serve as a good formula for making common ink, and will be enough to give an idea of the ordinary and general mode of its composition:—“Take of Aleppo galls finely bruised, six ounces,—sulphate of iron, four ounces,—gum Arabic, four ounces,—water, six pints. Boil the galls in the water for about two hours, occasionally adding water to supply the loss from evaporation; then add the other ingredients; and keep the whole for two months in a wooden or glass vessel, which is to be shaken at intervals. Then strain the ink into glass bottles, adding a few drops of creosote to prevent mouldiness.” Besides its property of viscidity, the gum possesses the power of preventing the ink from being too fluid: and it also serves to protect the vegetable matter from decomposition. The great desideratum or requisite is that the ink should flow with perfect freedom from the pen, to allow rapid writing, and that it should adhere to the paper, or “bite into it,” so as not to be effaceable by washing or sponging. The great defect to be avoided and prevented is the want of durability. The writing ink of the ancients was characterized by great permanency, being composed of finely pulverized carbon mixed with a mucilaginous or adhesive liquid. INDIA or CHINA INK is of this composition: it is formed of lamp-black and size or fine animal glue, with the incidental addition of perfumes. It is used in China with a brush, both for writing and painting on Chinese paper; and it is employed in other countries for making drawings in black and white,—the different depths of shade being produced by varying the degree of dilution in water. Inks of other colors than black were anciently used only for purposes of ornamental and decorative writing. In later and present times, red and blue inks have been extensively employed in ruling account-books and other paper for like uses. Blue ink, within ten or more years past, has been, with many, a preferred fluid for common writing. Blue ink, when properly made, flows with great ease and rapidity from the pen, dries almost instantly on the paper, and has been supposed or expected to be quite durable, and unchangeable in color, under ordinary vicissitudes. Yet, experience has demonstrated the contrary,—though various and well-contrived chemical combinations have been attempted for the purpose. Blue inks that change to black some time after writing are very popular. On well-made and high-priced paper, and with gold pens, such inks, if prepared by good chemists, may ultimately prove worthy of the high esteem in which they are held; but their absolute and unchangeable durability is yet to be tested by experience, before they can be safely employed for writings of permanent value, and relied on for use in making records designed for preservation and reference during a long course of years.