I thought little at first of the general public, when I began to weave together in narrative form the facts, letters, and journals contained in this volume. My chief object was to prevent the dispersion and final loss of scattered papers which had an unquestionable family value. But, as my work grew upon my hands, I began to feel that the story of an intellectual life, which was marked by such rare coherence and unity of aim, might have a wider interest and usefulness; might, perhaps, serve as a stimulus and an encouragement to others. For this reason, and also because I am inclined to believe that the European portion of the life of Louis Agassiz is little known in his adopted country, while its American period must be unfamiliar to many in his native land, I have determined to publish the material here collected.