summing up the results of these courses, Professor Silliman expressed a feeling of satisfactory assurance that he had popularized science; that at no period of his life had his efforts been more useful, both to his country and his family; and that there was no part of his professional career which he reflected upon with more satisfaction.
lie was accustomed to explain the success of his lectures, and the uninterrupted interest they attracted, by stating that he always prepared them "with all possible care, and arranged every experiment and illustration so as to insure success. Then I could stand before the largest audience without anxiety or embarrassment; could, without manuscript, clearly state and explain my subject, and, when the proof became necessary, I could perform the experiments successfully and even beautifully, and exhibit the specimens which some other truth demanded, to insure conviction."
In 1830 Professor Silliman made a visit of exploration to the valley of Wyoming and its coal formations, where he examined some hundred mines and localities of coal, extending through forty miles in length; in 1832-'33 he was engaged, under a commission from the General Government, in a scientific examination on the subject of the culture and manufacture of sugar; and in 1836 he made a tour of investigation among the gold-mines of Virginia.
In 1840 an association of geologists was formed in Philadelphia for the purpose of promoting the progress of their science and its applications in this country, and Professor Silliman was chosen its first president. This society was in time succeeded by the "American Association of Geologists and Naturalists," and the latter eventually became the "American Association for the Advancement of Science."
In 1849 Professor Silliman, having reached the age of seventy years, tendered a resignation of his professorship, to take effect at the end of the ensuing academic year. The corporation, only half accepting his resignation, requested him to continue his lectures in the department of mineralogy and geology, should his life and health be spared. Later, at the request of the corporation, he reconsidered his resignation, and continued in the full occupation of his professorship till 1853, when, "wishing to go out before he should be compelled by infirmity, and to march out of the camp with colors flying," he retired finally. "Thus," he remarks in his journal, after referring to the public notices that were taken of his retirement during commencement-week, "I have finished my regular connection with Yale College, after having been almost fifty-four years an officer of the institution—three years a tutor, fifty-one a professor, and almost fifty a lecturer. . . . I seem to have attended my own academic funeral, and many to be the mourners on the occasion." The corporation requested him to continue as a professor emeritus, with the right to vote in the academical and medical faculties. His professorship was divided, and he had the satisfaction of seeing his son placed in the chair of Chemistry, and