A far more ambitious undertaking was the preparation and publication of the large “Treatise on Chemistry,” in the writing of which he had the invaluable co-operation of his colleague Schorlemmer. The first volume appeared in 1877. It is so well known that no description of it is necessary. It is an eminently readable work, admirably printed and beautifully illustrated. Indeed, in style and appearance it is hardly approached by anything of the kind in the language. It was translated into German by Schorlemmer, and published by Vieweg & Son, and has now largely replaced the time-honoured Graham-Otto as a text-book in German colleges and technical schools. Unfortunately, owing to Schorlemmer’s death in 1892, the organic section in the English edition was never finished. It has, however, been completed in the German edition under the direction of the late Professor Brühl of Heidelberg—a circumstance which would seem to throw some light on the comparative position of organic chemistry in this country and in Germany. It ought, however, to be stated that if the whole of the organic section were compiled with the same attention to historical detail, and the same fullness of information that characterizes the inorganic portion, the work would become practically unsaleable on account of its size. At the time the treatise was planned the extraordinary expansion of organic chemistry which has occurred during the past forty years could hardly have been anticipated. It may be, as old Thomas Fuller wrote, that “learning hath gained most by those books by which the printers have lost.” But philanthropy is not the first business of publishers. The inorganic section of the English work has passed through several editions, and was thoroughly revised and largely re-written from time to time with the help of numerous collaborators. The fifth edition on “The Metals and their Compounds” made its appearance in the autumn of 1913—and is a goodly volume of nearly 1,500 pages. Roscoe, then in his eightieth year, worked hard at the revision and read the proofs with all the care and diligence he expended on the original work. Some time prior to 1895 he was induced by his friend, the late Sir Wemyss Reid, to undertake the editorship of the Century Series of Biographies of Scientific Men, projected by Cassell & Co. To this he contributed a popular account of the life and work of Dalton under the title of “John Dalton and the Rise of Modern Chemistry”—a little work which he wrote with much zest and a thorough appreciation of the fine character of the grand old Cumbrian Quaker.