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 _Chemistry_ had no existence till many centuries after Pliny wrote. And thus, it never occurred to him that there was but one substance, (now known to be elementary,) CARBON, which gave the quality of blackness to all the materials which he names, with the exception of one salt of copper, and probably one of iron, (the sulphate,) and INDIGO, a purely vegetable substance, the dried coloring matter of a plant in India, (_Indicofera anil_,) and named by the Romans from the country that produced it, and first made it known to them. PEDANIUS DIOSCORIDES, born in Anazarbus, (a city of Cilicia, about fifty miles from TARSUS, the birth-place of the Apostle Paul,) wrote a book on the Materia Medica, or the qualities of drugs, a little after the time when Pliny composed his Natural History. Neither of them seems to have been acquainted with the writings of the other. Apparently, they lived, wrote and died nearly or actually cotemporary, in the same empire, utterly ignorant of each other’s existence,—though they are now universally recognized as the two most eminent writers of all antiquity on the subjects of Natural History and the Materia Medica. They both lived in the reign of Nero, and the date of the active or middle part of both their lives may be reasonably placed at or about the year 100 of the Christian Era. From Dioscorides to LINNÆUS, (in the last century,) the Materia Medica made no actual progress and received no scientific improvement; yet, eminent as is Dioscorides, he was so little known to his own generation or that next following, that it is now impossible to ascertain the exact date of his birth or of his death, or any facts in his life, but that he wrote two books, of which that here quoted is the best known, and has made him known 1700 years after his birth. (We may mention that this Dioscorides was, in no traceable degree, related to the person of the same name, whose manuscript we have copied in our illustrations as the oldest extant specimen of Greek ink-writing.) We give a translation of his brief but complete description of the ink used in his time, and the Latin version, that those who wish may satisfy themselves of the correctness of our rendering. It will be seen that it occurs at the close of the great work of Dioscorides:—