was required not only to name the specimen, but also to give his proofs why this belonged to a certain species and not to any other.
After this laboratory work had been performed, the instructor passed on to the next group—the chlorides, etc., fluorides and oxides of Dana's system. Lectures with the succeeding laboratory work followed, but in the drawers for determination there were placed specimens not only of this group but also of the preceding group. This was followed throughout the year, so that the student was unable to lose sight of any species he had previously studied. Written examinations were occasionally interspersed, in which the student was required to determine a certain number of picked specimens that were placed before him, and write out the reasons for his determinations. This system of instruction, I believe, was devised by the teacher of the course at that time, Professor J. P. Cooke. After having endeavored to inform myself as to the methods of instruction in elementary mineralogy both in this country and in Europe, I have as yet failed to find one that, in my judgment, equals this, both for the mental discipline and the practical instruction it gives; and I take pleasure in acknowledging my great obligations and gratitude to Professor Cooke for the mineralogical instruction I received from him in that course.
When, in the process of time, this course passed under my charge, great modifications were made in it; the crystallography was reduced in amount and lithology added. By a different arrangement the crystallography was taught in six lectures. In these, by means of a few simple principles, the student was taught to recognize readily to which form the planes of any crystal belonged, no matter how many different forms might be represented. Further than this it did not seem practicable to go, without entering upon an extended course of instruction and practice in mathematical crystallography, which would have consumed the entire time of the course. However, it was found that the students were better trained for the practical application of crystallography to determinative mineralogy by this brief course than they had formerly been by the two and a half months' instruction previously given.
Another radical change was the substitution for the "general quiz" of all the students, at the lecture-hour, of an hour's oral examination for each student. Each one was required to arrange some hour in which he could meet the instructor alone in his room, with his (the student's) crystal models, or drawer of specimens, as the case might be. During that hour he was carefully questioned upon the material, and every effort was made to lead him to express his ideas clearly. He was cross-examined on every point, relating not only to general principles, but also to the particular specimens in hand. He was required to state what characters were upon the specimens, how he determined them, and what their relations were to others. If it was found that the student's methods were imperfect, his