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B21 1549 1923

PREFACE

In offering this work to my fellow teachers, a word of explanation is due.

The book was undertaken some years ago when the writer felt the want of a text-book adapted to the needs of students taking the general first year course in college. As the work has slowly progressed several text-books of very similar aim have appeared, and it must be admitted that the call is not so imperative now as formerly; and yet it is hoped that the treatment here presented may meet some still existing demand and so justify its existence.

What may be called the physical rather than the mathematical method has been preferred in giving definitions and explanations, because it is believed that the ideas presented are more easily grasped and more tenaciously held when the mind forms for itself a sort of picture of the conditions, instead of merely associating them with the symbols of a formula.

There are many minds that do not easily grasp mathematical reasoning even of a simple sort; and it is often the case also that a student who may be able to follow an algebraic deduction step by step has very little idea of the significance of the whole when he reaches the end. Algebra is not his native tongue and it takes considerable time and experience for him to learn to think in it. And while all will agree that for the more advanced study of physics, mathematics is quite indispensable, many will grant that in a general course, which is to furnish to most of those taking it all that they will ever know of physics as a science, the ideas and reasonings should be presented as directly as possible and in the most simple and familiar terms.

This then has been the central aim in the preparation of this book; to give the student clear and distinct conceptions of the various ideas and phenomena of physics, and to aid him in thinking through the relations between them, to the end that he may see something of the underlying unity of the subject; and to carry out this aim in such a manner that students may not be repelled by any unnecessary prominence of symbolic methods, and yet that the treatment may have all the exactness and

precision in statement and deduction which the subject demands. This is a large ambition and I cannot hope to have been wholly successful, but I shall be grateful if my attempt is found in any degree to have subserved its purpose.

My grateful acknowledgements are due to Dr. G. S. Fulcher of the University of Wisconsin, who has read nearly all the manuscript with great care, and to whom I am indebted for important suggestions, and to my colleague Professor J. O. Thompson whose criticism at all stages of the work and painstaking correction of the proof has been most helpful.

AMHERST, March, 1911.

A. L. K.

PREFACE TO REVISED EDITION

Recent advances in physical science having made it necessary to rewrite some paragraphs of the earlier edition, especially those relating to X-rays and the electron theory of matter, advantage has been taken of the opportunity to make a few additional changes which class-room experience has shown to be desirable. Certain paragraphs relating to force and motion, which had been introduced before the section on statics, are now placed among the introductory paragraphs to kinetics, where they fall in better with the logical development of the subject. The electromagnetic units, volt, ampere and ohm, are defined and introduced earlier than before. The sections on wireless telegraphy have been made more complete and wireless telephony is touched upon. A section also has been added treating of the flicker photometer. At the end of the volume a short discussion of Carnot's cycle and the thermodynamic basis of the absolute scale of temperature has been introduced as an appendix, also a proof is given of Newton's wave formula. Quite a number of new problems have been added, but the old problems have been found to serve their purpose well and are for the most part retained.

The author gratefully acknowledges his indebtedness to Dr. G. S. Fulcher, and to Professors W. E. McElfresh and D. C. Miller, for valuable suggestions and criticisms.

AMHERST, MASS.
July, 1917.

A. L. K.

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PREFACE TO THIRD EDITION

In this revision an attempt has been made to conform as closely as possible to that already outlined and started by Professor Kimball before his death, so that the book shall remain his work, and be representative of his ideas.

The book is a few pages longer than before because, although additions have been made, it seems inadvisable for the present to omit or to change the original material except in a very few places.

The writer recognizes the difficulty of the task he has undertaken. He hopes that his knowledge of Professor Kimball's ideals and methods of teaching physics from many years of association with him, together with his own experience as a teacher, is a sufficient reason for attempting it.

Acknowledgment is due especially to Professor F. A. Saunders of Harvard University whose suggestions and criticisms of the manuscript have been most helpful. Acknowledgment should be made also to Professors J. O. Thompson, W. K. Green, P. I. Wold, W. S. Kimball, and to many others who have aided in the preparation of this revision.

SCHENECTADY, N. Y.
July, 1923

A. L. K., JR.

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