increase his power to see, think, and do for himself, and to make him acquainted with the chemicals, methods of manipulation, reactions, and laws at first hand.

2. Have the pupil keep a laboratory notebook, and insist on the use of reasonably good English, on neatness, and on clearness, and that all entries shall be made when the experiment is performed. Full directions, some explanations, and questions are useful in the laboratory manual, but strictly guiding subheads are to be avoided. A loose-leaf system is an advantage.

3. The attention of the teacher must be given repeatedly to each individual student while in the laboratory.

4. Some problems should accompany the course in chemistry. These problems should always be practical and should be made more of a laboratory than a classroom exercise.

5. Do not have much exact measurement. A student may measure a thing exactly and know nothing about it; in fact, his mind is easily diverted from the real problem to the mechanical details of the measurement. Some science courses have been aptly called "starvation courses in measurements."

6. Sacrifice some of the experiments in the book for some more nearly "homemade." The added interest will repay the trouble.

7. Make the student think, but do not expect him to rediscover chemical laws or to prove them. A little consideration of any law will probably show you that you could not, if turned loose in the best chemical laboratory in the country, prove the law in six months. Let the experiments illustrate the laws; they will help the student to remember and to understand them.

8. Sometimes the student gets more results than he can take care of. He may not select the one that you had in mind. Do not expect him always to draw your conclusion without your assistance from an experiment assigned by you. (7: 194-195)

Principles of previous chapters apply. Most of the problems concerning the conduct of laboratory work fall under the general principles of instruction which we considered in previous chapters. The most important of these principles for our present purpose are those concerning (1) the selection of subject matter, (2) economy in management, (3) acquiring motor

skill, (4) reflective thinking. We shall discuss briefly the application of these principles to the conduct of laboratory exercises. Adapt laboratory exercises to broader social needs. The adaptation of the subject matter of laboratory instruction to the contemporary social needs of the various classes of students to be found in high schools would necessitate relating the experimentation very definitely to processes that play a large part in the practical affairs of ordinary people. In botany and zoology this would eliminate a large amount of the study of structure that has been so prominent in the past, and would lead to an emphasis upon the conditions of growth, physiological conditions, and the propagation, care, and uses of the plants and animals. In physics it would result in the emphasis upon experimentation with machines, with simple electrical devices such as bells and telephones, with practical applications of heat, etc. In chemistry, emphasis would fall upon the reproduction in miniature of important industrial processes. In all of these sciences the relations to agriculture often furnish important points of contact. In domestic science there is at present little danger of the experimentation being unrelated to social needs, although in some schools a student is required to struggle through several relatively unrelated courses in chemistry and other sciences before she is permitted to begin any experimental manipulation of food materials.

Exercise care in selection from superabundance of material. - The problem of relative values as applied to the teaching of science has already been illustrated in the choice between quantitative and qualitative studies in physics (see above, p. 71). To be sure, the use of the instruments of measurement employed in physical research would have some value for students, but the greater value of other activities is suggested by Hoadley in the following quotation :

With a superabundance of excellent material within the scope of elementary physics, there would seem to be no valid reason for

spending the first days in the laboratory on manipulation and measurement with vernier and micrometer calipers, the diagonal scale, the spherometer, etc., as is sometimes done with no physics in sight.

The more simply and directly a physical problem is presented to the pupil the better, that his thoughts and attention may not be diverted from the real point at issue. This principle is especially applicable in the early part of the laboratory course, where it is most frequently and most seriously violated by the use of micrometric instruments, the Jolly balance, etc., in the work on density and specific gravity, even before the pupil has had practice in the simpler methods of measuring and weighing. It would seem as if the express purpose of such work were at the outset to throw as many obstacles in the way of progress in physics as the ingenuity of teachers and instrument-makers could devise.

Perhaps the most striking illustration of what should not be done in this respect is afforded by the familiar quantitative experiments on the breaking strength of wires and on elasticity of stretching, bending, and twisting. These experiments lead absolutely to nothing in most high-school courses. The laws with which they deal are, for the most part, not considered in elementary textbooks. (10: 15-16)

The same type of argument would apply to all the other sciences in which there is an equal superabundance of material with equal necessity of exercising care in the selection of laboratory exercises that are relatively the most valuable.

Relate experimentation to a few large topics or problems. -The desirability of emphasizing a few large topics in experimentation is set forth by Mann as follows, with particular reference to physics :

Experience has taught us that the average teacher of physics is liable to err in requiring the class to study too many topics and do too many experiments. The result of such an error is that the pupils become confused and also acquire careless habits in the use of the apparatus and the making of measurements. (4: 175)

Not only is there danger of developing poor habits of experimentation when there are so many experiments, but there

is danger that the thought aspect of the work will be neglected altogether and the laboratory activity become a mere matter of hurried manipulation.

-The

Adapt to needs, interests, and capacities of students. arrangement of the subject matter for laboratory work in terms of the needs, interests, and capacities of the high-school students has already been emphasized in the discussion of the course in general science on pages 85-92, and need not be further elaborated here.

Economy would often justify substitution of lecture demonstrations. The second general principle which has an important bearing upon laboratory teaching is the principle of economy in classroom management. The application has already been made on page 35. Apart from the matter of economy in arrangement and manipulation of materials, however, there is always a larger question of economy; namely, whether the same real experiences could not be given more economically and effectively by having the teacher or a committee of capable students demonstrate the experiments before the class. In many cases, where observation and reflective thinking about real situations is more important than acquiring skill in manipulation, the demonstration is much superior to individual laboratory work. The time that is used by individual pupils in setting up apparatus could often be used to much greater advantage in reflective thought based on observation. In emphasizing this point Thorndike says:

Like any reform in education, the laboratory method has suffered at the hands of its friends, by being used indiscriminately and by being overused. It is not scientific to spend two hours in learning by manipulation of instruments something which could be better learned in two minutes by thought. Washing bottles, connecting electric wires, and putting away test tubes, though doubtless useful tasks in connection with scientific housewifery, are not magical sources of intellectual growth. Nor is it safe to disregard what is taught, so long as it is taught as an exercise in scientific method.