precision, and thoroughness, for it is believed that a proper understanding of them lies at the base of all scientific knowledge, however far it may be pursued. The book is adapted to students of fourteen years and upward, but by the occasional omission of an advanced paragraph, an algebraic expression, or an exceptionally difficult principle, the text becomes perfectly comprehensible to the most juvenile learners. Thus it is essentially fitted to pupils of different degrees of maturity. The easier principles may form the basis of a first year's course; while, in the second year, the student will find in the complete text additional matters which increased age and extended experience now enable him to grasp and appreciate. It has been the aim of the authors of this volume not to teach results merely, but to show how these results have been reached as well as what practical use is made of them, and thus to inspire the learner with enthusiasm in his work of questioning Nature. Precedence is everywhere given to the practical. The steam-engine, the electric motor, the telephone, and the telegraph, even the simplest tools, are shown to be machines or devices by which energy of some form is made to do work useful to man. The experiments, especially those described in the chapters on dynamics, etc., are largely intended as illustrations, and not as proofs; hence the pupil is not led to draw extended inferences from insufficient evidence-a habit antagonistic to proper and symmetrical mental development. Further, the significance of the algebraic formulæ is immediately impressed upon the learner by solved numerical examples. This feature is of special importance in the earlier discussions, where the abstract or general statements are rendered much more intelligible because accompanied with concrete forms. Instructive diagrams and illustrations have been introduced wherever it was thought they would relieve the text; suggestive questions, not intended to supersede minute examination by the teacher, but rather to exercise the reasoning faculties of the pupil, are inserted at such intervals as mark convenient and logical divisions into lessons; problems are appended to the several sections, to test the student's understanding of the principles therein explained; and applications of these principles in every-day experience render them delightful to learn and easy to remember. The illustrations not only reproduce the more complicated apparatus usually found in the school laboratory, but also elucidate the descriptions of simple experiments that can be successfully attempted by young people with home-made appliances. At the beginning of PREFACE. each principal section is pictured a suggestive group of such apparatus as will be found necessary to the performance of the experiments described in the chapter following; and, throughout the book, minute instructions are given for the cheap manufacture of essential pieces of apparatus. The publishers feel assured that the many valuable features of this new School Physics must recommend it to teachers as a singularly practical and authoritative text-book on the subjects of which it treats. NEW YORK, March 2, 1891. |