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have especial pleasure in calling the attention of science-teachers in our higher grades of schools to this timely and valuable text-book. Its title, "The New Physics," is appropriate in a double sense, and is, in fact, the true key to the understanding of its character and claims.

But at the outset let us say that Professor Trowbridge's book is not new in the sense of treating of all the latest scientific novelties. It is not a digest of information on physical subjects for instructive reading and convenient reference, and makes no account of "the latest things" which it is often thought desirable to get into school-books, to "bring them up to the present time."

But the work is new, in the first place, as representing a great step of advancement in the fundamental ideas and general view of the subject, which is now properly designated "the new physics." No one discovery in the whole sphere of scientific thought has ever proved to be so profound and far-reaching in its influence as what Dr. Faraday calls "the highest law in physical science"—the law of the conservation of energy. The older views of the nature and laws of forces—the radical problem in physics—have been left behind us, antiquated by the emergence of the great principle of correlation and conservation which gives us a new and grander conception of the method of Nature. Professor Trowbridge has first made this principle basal in the study of elementary physics, and has chosen a title for his book which marks the present advance of the subject, and sharply contrasts his treatment of it with that of the older expositions.

In the second place, the method of teaching adopted is new in the sense that it is a progressive step in total contrast with the old and still prevailing method. This book is a guide to the study of phenomena. The pupil is taken through a systematic course of experiment in the laboratory, doing his own observing, his own manipulating, and his own thinking, and thus making his acquisitions real. The literary method of studying science is entirely discarded, with its vague results and all the possibilities of coaching and cram. The pupil goes to work at the threshold, and with the assistance and direction of competent teachers, which it is assumed he will have, he carves his way, and becomes thoroughly grounded in the facts and principles of the subject. "The New Physics" thus conforms to the spirit and embodies the method of "the new education."

Physics can not be truly taught without a laboratory any more than chemistry; but the apparatus necessary is not very expensive. On this point Professor Trowbridge says:

An elementary laboratory of physics for a school, with experiments properly selected—for it is not necessary to cover the whole ground of experimental physics in order to gain a large amount of intellectual discipline—need not cost more than a chemical laboratory such as is now provided in many high schools. I have endeavored to describe only simple and inexpensive apparatus. The teacher can readily invent simple contrivances which, in many cases, will be better than those I have recommended. My endeavor has been to point out the way to a more rational method of studying physics. In the Appendix will be found additional directions for constructing simple apparatus. It is not supposed that the student will perform all the experiments in this treatise during the time that can be devoted to physics in the secondary schools. The choice of experiments by the teacher must necessarily depend upon the apparatus on hand, which can be modified for the purpose of this treatise, and upon the amount of appropriation which can be devoted to cheap apparatus.

It is frequently said that experimenting is more play than work, and that boys like it because it is easy. But this remark is not true of Professor Trowbridge's method of studying physics, in which, with regular manipulation, close thinking is enforced. This object is to secure that kind and measure of mental discipline which the study of physical science is capable of conferring; and that implies concentrated mental exercise upon actual laboratory processes, so as to arrive at accurate results. Of course, mathematics, the language of exactness, is indispensable, and is constantly used—arithmetic, algebra, geometry. But the amount of the latter needed to use the work is very moderate. Familiarity with simple equations and an elementary knowledge of square root are required, and, as explained by the author, as much trigonometry as can be got