There is some authority though for the statement that at this time two vitriolic substances were used in the preparation of black ink,--a slime or sediment (Salsugo) and a yellow vitriolic earth (Misy). This last-named mineral, is unquestionably the same natural chemical mentioned by writers, which about the end of the first century was designated "kalkanthum" or "chalkanthum" and possessed not only the appearance of, but the virtues of what we know as blue copperas or sulphate of copper. It continued in use as long as men were unacquainted with the art of lixiviating salt, or, in other words, as long as they had no vitriol manufactories. Commingled with lampblack, bitumen or like black substances in gummy water, it was acceptable to the priests for ritualistic writings and was in general vogue for several centuries thereafter under the name of (blue) "vitriolic" ink, notwithstanding the fact that there could not be any lasting chemical union between such materials. It was the so-called "vitriolic" ink, which is said to have "corroded the delicate leaves of the papyrus and to have eaten through both parchment and vellum." These deductions, however, do not agree with some of the historians and scholars like Noel Humphreys, author of the "Origin and Progress of the Art of Writing," London, 1855, a recognized authority on the subject of ancient MSS., who but repeats in part the text of earlier writers, when he says, p. 101: "Examples of early Greek MSS. of the last century previous to the Christian era are not confined to Egyptian sources; the buried city of Herculaneum, in Italy, partially destroyed about seventy- nine years before the Christian era, and injured by subsequeut eruptions, till totally destroyed by the most violent eruption of Vesuvius on record, that of the year 471 A. D. having yielded several specimens." The MSS. examples mentioned in the citation, must of necessity refer to specimens of writing made with "vitriolic" and even more ancient inks. They are to be considered in conjunction with the historical fact that these cities were buried for more than sixteen hundred years, counting from the first eruption, before they were brought to light (Herculaneum was discovered A. D. 1713 and Pompeii, forty years later); also that they must have been subjected to intense heat and a long period of decay which could only operate to rob them of all traces of natural ink phenomena. Furthermore, the information Mr. Humphreys seeks to convey, dates contemporaneously with the first eruption of Vesuvius, which occurred seventy-nine years AFTER the Christian era and not seventy-nine years BEFORE it.