18. The eye a camera. (See Section 84.) 



a. The parts of the eye. 



b. Proper care of the eyes. 



19. The telescope. 



Experiment 10. To make a simple tele- 

 scope. 



20. Sound 



a. Caused by vibrations. 



Experiment 11. Sources of sound. 



b. Carried by matter. 



Experiment 12. Sound not heard in a 

 vacuum. 



21. Velocity of sound. 



Experiment 13. Distances determined 

 by sound. 



22. The ear. 



a. The parts of the ear. 



b. The care of the ear. 



c. The Eustachian tube. 



23. Music and musical instruments. (See Section 85.) 



a. Vibrating strings. 



Experiment 14. The variation of pitch. 



b. Vibrating columns of air. 



Experiment 15. The whistle. The orgin 

 pipe. 



24. The voice. 



HEAT. VIII. 



25. A brief summary of the facts stated under the 



same topic in the work for the fifth, sixth, and 



seventh grades. 



