Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. Many of the experiments follow the course of instruction in elementary science contained in the physics and chemistry syllabus prepared by a Committee of the Incorporated Association of Head Masters. The results are indicated in each case, hence the experiments may be regarded in a way as solved examples of the general laws and phenomena Of physical science, but the examples can only be properly understood by actually following the various stages which lead to their solution. In a few sec tions of the book it has been necessary to illustrate by numerical examples the principles involved and to exercise the studentin solving simple problems of this kind numerous questions have been added to the chapters. For a large number of these, and more especially for those appended to Chapters III - VII, we are indebted to Mr. Walter J. Wood, who has collected many from actual examination papers, and has supplied the answers. Throughout the preparation of the following pages we have found the assistance and advice Of Professor R. A. Gregory invaluable. Teachers who know Professor Gregory's Exercise Book of Elementary Practical Physics will recognise in the earlier chapters of the present volume several experiments described in that book. The Opportunity of expressing thanks for permission to introduce these is gladly taken; and we also desire to express our Obligations to the Publishers for permitting free use of suitable illustrations from several of their elementary books in the various branches of science with which this volume is concerned.
