sea regarding the topic under discussion--the senses--as to force me to ask him, "With what do you hear?" and who answered with perfect sincerity, "I don't know." This was a psychological question, and as such became as difficult as the spelling of _cat_ at the end of a "spelling bee." When the student has been made to feel that the questions he is asked can be answered from his everyday experience, and that common sense is often quite as serviceable a guide as special knowledge, a progress ensues in every way satisfactory. Such a conviction, however, is not a matter of verbal acknowledgment; it yields slowly to explanation and proceeds somewhat unconsciously and inwardly. Moreover, it is a trait very sensitive to the power of contagion, so that a comparatively small proportion of the class may successfully spread this mental attitude to the whole number. A question which two or three have failed to answer becomes invested with a spurious difficulty which makes it a deep mystery to all the others. This mental prepossession may at times have quite different and curious results. When, for instance, the goal to be reached is given, when the answer may be looked up in the back of the book, it is surprising what peculiar and irrational steps will be taken to secure and justify the answer so given. This is all the more striking when the answer happens to be wrong; however simply such error may be discovered, the prepossessed mind will work away until by a more or less roundabout procedure the desired answer is reached. A noted professor of chemistry has an apt illustration of such a case. In a chemical test his assistant by mistake referred the class to the wrong bottle, so that the substance which the correct liquid would have dissolved could not be at all dissolved in the liquid actually used. However, on the professor's next round in his laboratory nearly every student assured him that the substance had dissolved, and a few went so far as to describe the precise manner of its dissolution.