The Meaning of Science 7 



explain them so far as possible by facts already known. This 

 explanation they call a hypothesis, that is, something that they 

 think is right but have not proved. Then they try out this hypoth- 

 esis in every way possible. If the explanation still seems to be 

 true it is then called a theory. After many tests and trials of the 

 theory thus formed, and probably after new and different experi- 

 ments have furnished further proof that the theory is right, it 

 becomes known as a law or principle. 



Popular Science Monthly. 



EXPERIMENTS LED TO THE COTTON GIN 



As a result of a series of experiments, Eli Whitney constructed, in 1793, a machine 

 that separated cotton fiber from cotton seed. 



Isaac Newton discovered the law of gravitation. It is said that 

 Newton's interest was aroused by seeing an apple fall from a tree 

 to the ground. He knew that the apple had no power of motion 

 and, therefore, that some outside force must have caused it to fall. 

 He studied many other falling objects and from what he saw he 

 made the hypothesis that all bodies are attracted to the earth in 

 one and the same way. He also studied the motion of the planets 

 around the sun and the motion of the moon around the earth. 

 At last he announced the theory that all bodies are attracted toward 



