In the same year Dr. Persifor Frazer of Philadelphia published his "Manual of the Study of Documents." A few pages are given to the study of inks, and a part thereof is devoted to the researches of Carre, Hager, Baudrimont, Tarry, Chevallier and Lassaigne, to determine suspected forgeries. The chapter on "the sequence in crossed lines," where he indicates his method of determining which of two crossed ink lines was written first, is both original and a real contribution to science. Alfred H. Allen, F. C. S., of England, perhaps the highest authority on the subject of tannins, dyes and coloring matters in his "Commercial Organic Analysis," revised and edited by Professor J. Merritt Mathews of Pennsylvania, edition of 1900, devotes eight pages to the subject of the "Examination of Ink Marks." He says: "Ordinary writing ink was formerly always made from a decoction of galls, to which green vitriol was added. Of late, the composition of writing inks has become far less constant, aniline and other dyes being frequently employed, and other metallic salts substituted for the ferrous- sulphate formerly invariably used. The best black ink is a tanno-gallate of iron, obtained by adding an infusion of nut-galls to a solution of ferrous- sulphate (copperas)." In 1897 the author in a paper read before the New York State Bar Association at Albany, entitled "A Plea for the Preservation of the Public Records," discussed the question of the stability of inks and their phenomena and took occasion to make recommendations as to their constitution and future methods of employment. A vote of thanks was adopted and the association referred the paper to the Committee on Law Reform, where no doubt it still slumbers. CHAPTER XVI. ENDURING INK. ASCERTAINMENT OF A CORRECT INK FORMULA THE WORK OF OVER A CENTURY--CHARACTER OF THE EVIDENCE WHICH ESTABLISHES IT--THE INVESTIGATIONS OF THE AUTHOR IN THIS DIRECTION AND COMPARISON WITH THOSE OF COMMISSIONER SWAN--ELIMINATION OF THE "ADDED" COLORS AND THEIR ORIGIN-- DISCUSSION OF THE RELATIVE MERITS OF LAMPBLACK, MADDER AND INDIGO--THE DURABLE VIRTUES OF INDIGO WHEN EMPLOYED ALONE--CAUSE OF THE BROWNING OF INKS--LONGEVITY OF INK DUE TO VEHICLE WHICH CARRIES IT--WHEN PERFECT INK WILL BE INVENTED. TO ascertain the correct formula of a substantially permanent ink, as we have learned, has been the aim during a century or more, of able chemists, manufacturers and laymen. Their experiments and study of ancient and modern documents all point unerringly in the direction of an ink containing iron and galls.