2. Study of the qualities of materials is a prominent part of lessons on objects. Such study is really the study of physical science, but with objects such as are usually selected is a very difficult part to give to young children. Ask the student who has taken a course in chemistry whether the study of the qualities of metals and their alloys is easy work. Ask him how much can readily be shown, and how much must be taken on authority. Have him tell you how much or how little the thing itself suggests, and how much must he memorized from the mere book statement and with difficulty. Study of materials is good to a certain extent, but it is often carried much too far. Consider a conversational lesson on some animal. Lessons are sometimes given on cats. As an element in a reading lesson--to arouse interest--to hold the attention--to secure correct emphasis and inflection--to make sure of the reading being good: such work is appropriate. But let us see what the effect upon the pupil is as regards the knowledge he gains of the cat, and the effect upon his habits of thought and study. The student gives some statement as to the appearance--the size--or some act of his cat. It is usually an imperfect statement drawn from the imperfect memory of an imperfect observation. And the teacher, having only a _general knowledge_ of the habits of cats, can correct in only a general way. Thus habits of faulty and incorrect observation and inaccurate memory are fastened upon the child. It is no less by the correction of the false than by the presenting of the true, that we educate properly. Besides this there is the fact that traits, habits, and peculiarities of animals are not always manifested when we wish them to be. Suppose a teacher asks a child to notice the way in which a dog drinks, for example; the child may have to wait until long after all the associated facts, the reasons why this thing was to be observed--the lesson as a whole of which this formed a part--have all grown dim in the memory, before the chance for the observation occurs. Pictures are less valuable as educational aids than objects; at best they are but partially and imperfectly concrete. The study of pictures tends to cultivate the imagination and taste, but observation and judgment are but little exercised. A comparison of the kind of knowledge gained in either of the above ways with that gained by a study of science as such, will make some of the advantages of the latter evident. An act of complete knowledge consists in the identifying of an attribute with a subject. Attributes of quality--of condition--of relation, may be gained from lessons in which objects or pictures are used. Attributes of action which are unregulated by the observer may be learned from the study of animals. But very little of actions and changes which can be made to take place under specified conditions, and with uniformity of result, can be learned until physical science is drawn upon.