Pictures of apparatus and descriptions of experiments should, of course, not be despised or neglected. They are helpful in forming concepts of that which cannot be brought before a class. When made by the learner himself, as a result of his own work, they serve to clarify his thinking, and furnish a sure test of the pupil’s progress and of the teacher’s skill as a guide and instructor. A drawing, or even a statement in the pupil’s own words, is often an astonishing revelation of the crude notions which pictures give. The city lad who said that a cow was no bigger than a finger-nail because he had often measured its size in the First Reader is a typical example. The ability to interpret pictures and descriptions comes from actual knowledge of things similar to what is depicted or described. The noted teacher, Agassiz, made a difference in his directions to beginners and advanced students. To the former he would give specimens, with directions to study them without referring to a book. Having taught them how to use their eyes, he would gradually lead them to the method of interpreting and verifying the statements of an author. And when the advanced student was set to work at original investigations, he was told to study certain books, as it would save much valuable time. One of his pupils writes, “I shall never forget a forceful lesson given me by the great Agassiz, when I studied with him in the Museum of Cambridge. I worked near a young man from Cleveland, Ohio, who has since achieved distinction as a teacher of biology. I was comparatively a beginner, however, while he was well advanced in his studies. On a certain day Agassiz came sauntering by, and stopped long enough to tell me not to use the library so much, but to confine myself to observations of the specimens on hand and the writing of my observations and comments. Passing on a little farther, he spoke to my friend and said, ‘Albert, when you go home, this summer, to Cleveland, I wish you would make a special study of a certain kind of fish found in the harbor there. It is not found plentifully anywhere else in the world. Take a row-boat and go three hundred yards northeast of the point of the breakwater, and you will find them in abundance. Before going home, get the only three books ever written on this fish from the library here and read them. It will save your time to read them before beginning to study the fish itself.’”[3] Agassiz was as anxious to teach the right use of books as is the professor of literature; but he adapted his directions to the degree of advancement which his students had attained, and did not neglect the formation of the basal concepts and the habits of study needful in the sciences he taught.