756 THE POPULAR SCIENCE MONTHLY. 



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 fol- 

 lowed, but in the drawers for determination there were placed speci- 

 mens 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 exami- 

 nations were occasionally interspersed, in which the student was re- 

 quired 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 min- 

 eralogy 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 disci- 

 pline 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 crys- 

 tallography 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 prac- 

 ticable to go, without entering upon an extended course of instruction 

 and practice in mathematical crystallography, which would have con- 

 sumed the entire time of the course. However, it was found that the 

 students were better trained for the practical application of crystal- 

 lography to determinative mineralogy by this brief course than they 

 had formerly been by the two and a half months' instruction previ- 

 ously given. 



Another radical change was the substitution for the "general 

 quiz " of all the students, at the lecture-hour, of an hour's oral ex- 

 amination 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 speci- 

 mens, how he determined them, and what their relations were to oth- 

 ers. If it was found that the student's methods were imperfect, his 



