PREFACE v 



and explanation are given both in the text and in the glossary 

 for the complete understanding of technical terms used in this 

 course. 



When only a half-year is devoted to General Science the 

 author suggests that the order of the book be followed to the 

 end of Chapter XXIV and then if more time remains the teacher 

 can select from the remaining subjects what will be most useful 

 to the pupils. It is hardly possible to cover the entire book in 

 a half year's work so that the pupils will get a definite and last- 

 ing impression of the principles underlying the subject-matter. 



The field covered in this course may at first sight seem broad 

 and varied, but there are two or three basic ideas which have 

 a broad application and which the mass of simple facts helps 

 to develop into clear concepts. These basic ideas are matter, 

 its properties, and how matter affects other matter, the re- 

 action of matter upon matter; and energy as a property of 

 matter. Pupils should be required to draw generalizations 

 from known facts wherever possible. The general ideas thus 

 acquired will remain with the pupils, although many of the 

 details may be forgotten. If no generalizations are acquired, 

 the pupil's mind will be blank after the details have evaporated. 

 The pupils who have detailed facts continuously heaped upon 

 them without general truths leave our educational institutions 

 uneducated. They are the ones who may recall that they 

 studied a certain subject while in school, but not much more. 

 Many detailed facts will remain with a general truth through 

 the process of mental association. 



The author would suggest that this book is in no case intended 

 to take the place of the live teacher. It is intended to furnish 

 material and suggestions for class discussion and to stimulate 

 the minds of pupils so that they may think about their experi- 

 ences and acquire more. There are in the course some sug- 

 gestions which will cause pupils to reflect on the past history 

 of man and to seek for the new in the present and future. The 

 illustrations, drawings and photographs, are given in series 

 wherever possible, so that a more definite idea may be acquired, 



