The author was led to the investigation of this subject by its connection with that branch of Medical Jurisprudence which treats of the prevention and detection of forgery.

It is well known that common writing-ink maybe totally effaced from paper by certain chemical agents, and that several others so impair its colour, that the characters traced with it become illegible. To the first class of chemical agents belong chlorine, and substances containing it, as well as oxalic acid; to the second diluted solutions, or the vapours of the mineral acids, and of the caustic alkalis. These agents were applied to written specimens of a great number of different inks, and the degree of resistance to their effects was considered as the criterion of the durability of each.