MISCELLANEOUS PROBLEMS. 527 



These essential elements and the percentage that they form 

 of the earth's crust are given in the following table : (According 

 to Clark.) 



Oxygen 47.00 



Hydrogen 17 



Carbon 12 



Phosphorus 09 



Potassium 2.32 



Iron 4.64 



Calcium 3.50 



Magnesium 2 . 62 



Sulphur 0.07 



There are four other elements that are of less importance. 



Chlorine 0.01 



Sodium 2.63 



Aluminum 8.16 



Silicon . . 28.06 



PROBLEM. 



1. What part of the earth's crust is composed of the following food 

 elements of importance: P. H. C. P. K. Fe. Ca. Mg. S.? 



Practical Problems. 



1. Have the class in agriculture get a tape line and measure the 

 school grounds and find area. 



2. Measure outside walls of school building and find area occupied 

 by building. 



3. Find the height of several of the tallest. trees in the school yard. 



4. Find the height of the highest point on the school building. 



5. Have each pupil find distance walked each day in going to and 

 from school. 



6. Have the class lay off a rectangle 40 by 60 on the school ground, 

 using only a tape measure. 



7. Demonstrate how a board can be marked so that it can be sawed 

 off square; do this without using carpenter's square. 



8. Demonstrate how to make a mitre box. 



9. Have pupils make drawings for constructing a gate 4.5 ft. by 

 14.5 ft. Make drawings for a barn door 4.5 ft. by 7.5 ft. 



10. Draw plans for a wagon box of proper dimensions that will 

 have a capacity of 30 bushels; how many feet of lumber will be required 

 to build it? 



