164 MECHANICS 



14 for full directions for the use of blue - print paper. 

 Section 70 tells how to make blue-print paper. 



Review Questions, 26. 



1. How many hours of sunlight were there yester- 

 day? How many hours without sunlight were there last 

 night? 



2. What is the direction of sunset now? How can 

 you tell the direction of sunrise without seeing the sun 

 rise? 



3. What is a flame? Prove your answer. Why 

 does charcoal burn without a flame? 



4. What are some of the ways of keeping food 

 from spoiling? Which is the worst method? Why? 



5. Why is the farmer's occupation the most im- 

 portant? Explain. 



6. What are some of the advantages of the French 

 system of measurement? 



7. Explain why it is better to use the larger weights 

 before using the smaller ones in weighing. 



8. When you blow through a tube into a liquid 

 what is inside the bubbles? What does this show? 



9. What is meant when it is said that the density of 

 one body is greater than that of another body? 



10. Besides talking and writing, how else can you 

 express an idea? 



63. Forces. 



Any push or pull is called a force. Weight is a pull 

 between the object and the earth and, as we have learned, 

 is called the force of gravity. When we say that a body 

 weighs five pounds we mean that the pull between the 



