Experiment 69. The reaction water 

 wheel. 



76. Measurement of rotary motion. 



a. Revolutions per minute. 



b. Velocity of point on circumference of wheel. 



Experiment 70. Velocity and number of 

 revolutions. 



77. Centrifugal force. (See Section 98.) 



Experiment 71. Centrifugal force. 

 (These subjects, Mechanics, are continued in the 

 work for the eighth grade.) 



MAGNETISM AND ELECTRICITY. VII. 



78. A brief summary of the facts stated under the 

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



79. Sources of electricity. 



a. Friction. 



Experiment 72. Electricity from friction. 

 The Leyden jar. 



b. Chemical. 



Experiment 73. The simple cell. 



80. Heat and light from electricity. 



Experiment 74. Electricity produces 

 heat and light. 



81. Chemical effects of electricity. 



Experiment 75. Electroplating. 

 (These subjects, Magnetism and Electricity, are 

 continued in the work for the eighth grade.) 



THE ARTS AND INDUSTRIES. VII. 



82. Business and nature. 



83. The chemical analysis of cloth. 



Experiment 76. Testing silk, linen, 

 wool, and cotton. 



