PREFACE ix 



to the future citizen rather than the future scientist, 

 to general readers rather than technical students. The 

 present book follows one of the many possible outlines 

 for such an introduction and constitutes a suggestion 

 as to one of the changes in teaching methods which 

 our educational system seems to require. 



The general reader is under no compulsion from a 

 traditional curriculum and may pick and choose his 

 sources of information. To the study of science he 

 may, however, need an introduction and this need the 

 present volume attempts to satisfy. The earlier 

 chapters following an historical order develop without 

 abstract formulations the fundamental concepts of 

 modern science. By the time Chapter IX is reached 

 the necessity of algebraic expression has become 

 apparent and the three succeeding chapters illustrate 

 its usefulness while developing the ideas of defining 

 equations, rates, and the laws of motion. Not all 

 these ideas are symbolized and the reader who feels 

 an ineptitude for mathematical expressions is advised 

 to give these chapters a cursory and mechanical reading 

 in order to reach the important chapters on molecular 

 and electronic motions. 



The majority of readers will probably find no 

 obstacles in the occasional formulas of the later text. 

 For these the book may serve as an introduction to the 

 general literature of physical science. To this end 

 footnotes refer to books on special subjects, the greater 

 portions of each of which the reader will find compre- 

 hensible in case he is interested in more detailed study. 



The writer wishes to make an acknowledgment to 

 the Physics Department of Mount Holyoke College, 



