15. The intensity of Tight in relation to distance. 



Experiment 15. The intensity of light 

 determined by a shadow, 



16. The measurement of light. 



a. The candle-power. 



b- Measurement by shadows. 



Experiment 16. The shadow photo- 

 meter. How made and how used. 

 'C. Measurement by translu'cence. 



Experiment. 17. The paraffin block 

 photometer. How mad^e and how used. 



17. Lenses. 



a. Convex. 



b. Concave. 



Experiment 18. Lenses are prisms. The 

 reducing glass. 



18. Images from a convex lens. 



a. Magnified and upright. 



Experiment 19. The magnifying glass, 



b. Real, both large and small ; inverted. 



Experiment 20. Images on a screen. 

 (This subject, Light, is contined in the work 

 for the eighth grade.) 



HEAT. VIL 



19. A brief summary of the facts stated under the 

 same topic in the work for the fifth and sixth grades. 



20. Heat causes boiling. 



a. Boiling temperature raised by dissolved sub- 

 stances. 



Experiment 21. Boiling temperature of 

 solutions. 



b. Boiling temperature raised by increased 

 pressure. 



