GENERAL SCIENCE 



PART I. THE AIR 



CHAPTER I 

 INTERESTING THINGS ABOUT THE AIR 



1. Introduction. What men can do and where and how 

 they can live often depend upon the atmosphere which sur- 

 rounds us. Because of our constant dependence upon the 

 air, there are many common questions which it is interesting 

 to consider. We can answer most of these questions from 

 our own previous experience, from experiments and observa- 

 tions we may make, or from written statements of the expe- 

 rience of others. The following are some of these questions, 

 and as these are considered, and as experiments are performed 

 and the text is read, each pupil will doubtless think of other 

 questions about which he would like to know. 



The questions which appear at the beginning of each chap- 

 ter of this book are not intended to be answered fully when 

 work on the chapter is begun. They are provided in order 

 to add meaning to text discussions and to experiments and 

 demonstrations. When work on each chapter is begun, the 

 questions should be read and discussed briefly. At the close 

 of each chapter the class should return to the questions 

 and problems and make sure that all can be satisfactorily 

 answered. The questions given show clearly the kind of 

 significant problems which should be constantly in mind. 



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