In order not to interrupt the course of the narrative, the history of this undertaking in its sequence and general bearing on his life and work may be completed here in a few words. This school secured to him many happy and comparatively tranquil years. It enabled him to meet both domestic and scientific expenses, and to pay the heavy debt he had brought from Europe as the penalty of his "Fossil Fishes" and his investigations on the glaciers. When the school closed after eight years he was again a free man. With an increased salary from the college, and with such provision for the Museum (thanks to the generosity of the State and of individuals) as rendered it in a great degree independent, he was never again involved in the pecuniary anxieties of his earlier career. The occupation of teaching was so congenial to him that his part in the instruction of the school did not at any time weigh heavily upon him. He never had an audience more responsive and more eager to learn than the sixty or seventy girls who gathered every day at the close of the morning to hear his daily lecture; nor did he ever give to any audience lectures more carefully prepared, more comprehensive in their range of subjects, more lofty in their tone of thought. As a teacher he always discriminated between the special student, and the one to whom he cared to impart only such a knowledge of the facts of nature, as would make the world at least partially intelligible to him. To a school of young girls he did not think of teaching technical science, and yet the subjects of his lectures comprised very abstruse and comprehensive questions. It was the simplicity and clearness of his method which made them so interesting to his young listeners. "What I wish for you," he would say, "is a culture that is alive, active, susceptible of farther development. Do not think that I care to teach you this or the other special science. My instruction is only intended to show you the thoughts in nature which science reveals, and the facts I give you are useful only, or chiefly, for this object."