Experiment 4. Stalactites and stalag- 

 mites. 



8. Rocks that once had life. 



Experiment 5. Organic rock. 



9. Coal. (See Section 82.) 



a. Soft. 



b. Hard. 



10. Other forms of carbon. 



11. The sun the source of all energy. 



12. Natural gas. 



13. Petroleum. 



Experiment 6. The distillation of petro- 

 leum. 



14. Mountains. 



a. How made. 



Experiment 7. Folded and block moun- 

 tains. 



b. As barriers. (See Section 95.) 



LIGHT. VIII. 



15. A brief summary of the facts stated under the 



topic in the work for the fifth, sixth, and 

 seventh grades. 



16. The velocity of light. 



17. Photography. (See Section 83.) 



a. The lens. 



Experiment 8. The camera lens. 



b. The sensitive plates and papers. 



Experiment 9. Why we can make photo- 

 graphs. 



