name of trygynon. Apelles, we are told, made his from burnt ivory, and called it elephantina "ivory-black." Indigo has been recently imported,—a substance whose composition I have not yet investigated. The dyers make theirs from the dark crust that gradually accumulates on brass-kettles. Ink is made also from torches (pine-knots), and from charcoal pounded fine in mortars. "The cuttle-fish" has a remarkable quality in this respect; but the coloring-matter which it produces is not used in the manufacture of ink. All ink is improved by exposure to the sun's rays. Book-writers' ink has gum mixed with it,—weaver's ink is made up with glue. Ink whose materials have been liquified by the agency of an acid is erased with great difficulty."
This sounds very much like nonsense: but it is exactly what the "Great Naturalist," Pliny, meant when he wrote all that he knew, and probably all that was then known on the subject of ink, black paints and dyes, and very dark-colored fluids generally, which were then employed by painters, dyers, weavers, writers and physicians. To make his chapter on this subject fully intelligible to us, we must bear in mind the fact, that the great science of Che-
