PUBLIC LIBRARY ASTOR, LENOX AND TILDEN FOUNDATIONS. 1897. LONDON: GILBERT AND RIVINGTON, PRINTERS, ST. JOHN'S SQUARE. ADVERTISEMENT. In laying the following sheets before the Public, it may, perhaps, be proper for the Editor to state, that those parts of the present publication for which he is responsible, have gradually grown under his hands to a more considerable bulk than he at first contemplated. This increase was the natural result of a desire on his part, to render the work as useful to his readers as was in his power, and at the same time to vindicate the title of his venerable friendfor such he had the privilege of esteeming the author -to the gratitude of the world. With regard to the evidences, which in consequence of the latter design, may occasionally appear, of the Editor's personal regard and affection for that great man, of whose extensive labours in the domains of science, the following Letters are a small, though an important |