That modern inks do not resist the decomposing and destructive power of chemical agents (whether acids, alkalies, saline bodies or elements,) as well as the ancient inks, is the result of a necessity existing in their very composition and invention, and even in the use for which they were designed, and to which they are applied. A _dye_ (like modern ink) is the result of chemical action, and is therefore subject to chemical re-agents; yet, when well made, it is proof against mechanical action, such as washing, rubbing, and scraping; nor can it be removed from paper to which it is applied, without destroying that material, or rendering that part of it practically useless. But, on the other hand, the ancient inks, which resist all chemical processes, can be removed by mechanical action, such as has been named. If a new ink were compounded of the two, possessing the best properties of each, any writing executed with it could be effaced by the joint or successive action of mechanical and chemical applications. It must be borne in mind that the ancient inks had one use for which writing ink is now never required; and that was in making books, or multiplying copies of manuscripts indefinitely for _general reading_, or _publication_. The invention and universal employment of the art of printing has wholly done away with that. Of INDELIBLE INKS, or those used for marking fabrics of cotton, linen, &c., for the identification of ownership, it is not necessary to give any particular description. Their ordinary composition is very generally understood to be a solution of nitrate of silver, or some similar caustic, applied with a pen of proper material, to a portion of the surface of the cloth, which has been previously prepared by the absorption of a gummy or mucilaginous fluid dried upon it under pressure. SYMPATHETIC INKS are fluids employed in coloring drawings made for parlor amusement, or the diversion of children and youth. As, for instance, a landscape drawn in ordinary colors with a wintry aspect, cloudy or sombre sky, snow on the ground, and leafless trees, if properly touched with sympathetic inks, will, at any time, when brought near a fire, or otherwise subjected to a certain degree of warmth, change to the hues of summer, the sky becoming of a clear blue, the trees in full foliage, and the turf rich with grass, each with its appropriate shade of verdure, as also flowers of their various natural colors, &c., according to the fancy of the artist, the whole disappearing as the picture grows cold. The chloride, the nitrate, the acetate, and the sulphate of cobalt, form sympathetic inks,—the first, blue, and (with the addition of nickel,) green; the second, red. Chloride of copper gives a gamboge yellow; bromide of copper, a fine rich brown.