"In a conversation some time ago with my friend Thomas Astle, Esq., F. R. S. and A. S., relative to the legibility of ancient MSS. a question arose, whether the inks in use eight or ten centuries ago, which are often found to have preserved their colour remarkably well, were made of different materials from those employed in later times, of which many are already become so pale as scarcely to be read. With a view to the decision of this question, Mr. Astle obligingly furnished me with several MSS., on parchment and vellum, from the ninth to the fifteenth centuries inclusively, some of which were still black, and others of different shades of colour, from a deep yellowish brown to a very pale yellow, in some parts so faint as to be scarcely visible. On all of these I made experiments with the chemical re-agents which appeared to me best adapted to the purpose, namely, alkalis both simple and phlogisticated, the mineral acids, and infusions of galls. "It would be tedious and superfluous to enter into a detail of the particular experiments, as all of them, one instance only excepted, agreed in the general result, to shew that the ink employed anciently, as far as the above-mentioned MSS. extended, was of the same nature as the present; for the letters turned of a reddish or yellow brown with alkalis, became pale, and were at length obliterated, with the dilute mineral acids, and the drop of acid liquor which had extracted a letter, changed to a deep blue or green on the addition of a drop of phlogisticated alkali; moreover, the letters acquired a deeper tinge with the infusion of galls, in some cases more, in others less. Hence it is evident, that one of the ingredients was iron, which there is no reason to doubt was joined with the vitriolic acid; and the colour of the more perfect MSS. which in some was deep black, and in others purplish black, together with the restitution of that colour, in those which had lost it, by the infusion of galls, sufficiently proved that another of the ingredients was a stringent matter, which from history appears to be that of galls. No trace of a black pigment of any sort was discovered, the drop of acid which had completely extracted a letter, appearing of an uniform pale ferrugineous color, without an atom of black powder, or other extraneous matter, floating in it.