HOW DO WE GET ACQUAINTED WITH THINGS? 9 



evidence have you that breaking a mirror carries bad 

 luck with it, or that a black cat crossing your path means 

 bad luck, or that walking under a ladder will be harmful ? 

 A moment's thought will show you that there is no 

 evidence for the truth of these superstitions. Every 

 boy or girl who studies science should determine that he 

 will carry over into his daily life this way of looking at 

 science problems. You may be sure it will mean much 

 to your peace of mind now as well as make you a more 

 intelligent and thoughtful citizen. 



Use of Workbooks. Every pupil should keep a note- 

 book in which are recorded observations and facts noticed 

 and learned demonstrations, statements made by the 

 teacher, and notes from supplementary readings. Outline 

 drawings of the apparatus used in some of the experi- 

 ments, and of the machines, animals, or plants, which he 

 wishes to remember, should be in this book which we will 

 call a workbook. When the work of each unit is organized 

 for review, an outline form of the unit should be recorded, 

 as well as brief but clear reports of special projects, ex- 

 periments, labeled diagrams, and figures which are neces- 

 sary for a clear understanding of the various problems of 

 the unit. Finally, the workbook may contain a collection 

 of clippings, pictures, and photographs, related to the vari- 

 ous topics. Your workbook will be something that you 

 can keep after your course is finished. It will not only be 

 a memento of a worth-while bit of individual work, but it 

 also will serve as a reference book to be used if you go on 

 with the subject of science. 



How to Use the Self-Testing Exercise. In the pages 

 that follow we shall find at the end of each problem a self- 

 testing exercise ; the object of this exercise is to help you 

 master the problem which it closes. To make the best 

 use of this exercise, you should place the numbers of the 

 blank spaces in columns on a sheet of paper. Then read- 



