10 FIE8T TEAE SCIENCE 



Newton many years ago discovered that all bodies of 

 matter have an attraction for each other and that this 

 force of attraction varies as the masses of the bodies, 

 that is, the more matter two bodies contain the more they 

 attract each other. But this attraction becomes less as 

 the distance between the bodies increases. This lessening 

 of the force of attraction on account of the increase of 

 distance is proportional not to the distance, but to the 

 square of the distance. This means that the attraction 

 between the same bodies when twice as far apart is only 

 one fourth as great; when three times as far apart, one 

 ninth as great, and so on. What causes this attraction no 

 one knows, but the name given to this force of attraction 

 is Gravitation. Gravitation is always acting upon all 

 bodies, and their conduct is constantly affected by it. 

 It keeps the heavenly bodies from wandering away from 

 each other just as the rubber band kept the weight from 

 flying away from the hand. 



When this attraction is considered in relation to the 

 earth and bodies near its surface the term gravity is used. 

 We are constantly measuring the pull of gravity and call- 

 ing it weight. This is the cause of bodies falling to the 

 earth. It is the force which causes us to lie down when 

 we wish to sleep comfortably, and frequently makes us fall 

 if we try to fly. 



If two forces act upon a free body, each will influence 

 the direction of its motion and it will go in the direction 

 of neither force, but in a direction between the two. If 

 there are more than two forces, the path will be the result 

 of the action of all the forces. In the case of the weight 

 and the rubber band we found that the moving weight 

 when not held by th'e force of the band flew away from 

 the hand. The rubber band continually pulled it toward 

 the hand. The result of these two forces, the inertia 



