A YEAR IN SCIENCE 



33 



same time noting any changes in the reading on the 

 index of the balance. Continue to lift the balance. 

 What happens? Examine the under surface of the 

 plate. What do you find there? 

 Does this indicate that the plate 

 was separated from the water or 

 that the water particles were 

 pulled apart? 



Thus it will be seen that two 

 forces were acting, the one holding 

 the molecules of water together, 

 called cohesion, the other holding 

 the plate to the water, adhesion. 

 Which in this ex- 

 periment was the 

 greater? With the 

 water still adhering, 

 hold the plate in 

 a vertical position. 

 What happens to the 

 water? This third 

 force causing the 

 water to drop is"" 

 called gravity. 



Which of these 

 forces acts between Fir - 13 - 



molecules of the same kind? Between molecules of 

 different kinds? Between masses? 



