b. The force pump. 



c. The air compression pump. 



Experiment 40. The simple air com- 

 pression pump. 



34. The siphon. (See Section 90.) 



Experiment 41. Siphons. 



35. Humidity in the air. 



a. Dew. 



b. Frost. 



c. Fog. 



d. Clouds. 



Experiment 42. Forms of water in the 



air. 



(This subject, Air, is continued in the work for 

 the eighth grade.) 



WATER. VII. 



36. A brief summary of the facts stated under the 

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



37. The warming of water. 



a. Water requires more heat than other mate- 



rial to become warmed. 



Experiment 43. The heat capacity of 

 water. 



b. The effect upon nature, 



38. The ocean and other large bodies of water. 



a. Source of food. 



b. Transportation. 



39. Waves. 



a. In water. (See Section 91.) 



b. In air sound. 



c. Other waves light and electric. 



Experiment 44. Waves in water and in 

 air. 



