OBJECTS.] INTRODUCTORY. 27 



19. The cause of Weight : Attraction : 

 Force. 



We know nothing whatever of the reason why 

 bodies possess weight. Bodies do not fall on account 

 of the law of gravitation ( 9); nor does their gravity 

 explain why they fall. Gravity, as we have seen, is 

 only a name for weight, and the law of gravitation is 

 only a statement of how bodies approach one another, 

 not why they do so. 



It is often said that gravitation is attraction, and 

 that bodies fall to the earth because the earth attracts 

 them. But the word " attract " simply means to " draw 

 towards," and "attraction" means nothing but "draw- 

 ing towards " and to say, when two bodies move to- 

 wards one another, that they are " drawn towards " one 

 another, is simply to describe the fact and makes us 

 no whit wiser than we were before. On the contrary, 

 unless we take great care, it may make us a little less 

 wise. For the words " drawing towards " are so closely 

 associated with ropes and hooks and the act of pulling, 

 that we are easily led to fancy the existence of some 

 analogous invisible machinery in the case of mutually 

 attractive bodies. 



Again, gravitation is spoken of as a force ; and 

 as the word force is in very common use, let us try to 

 make out what we mean by it. A man is said to exert 

 force when he pushes or pulls anything so as either to 

 exert pressure upon it or to put it in motion. A 

 wrestler's force is proved by his hug ; a bowler's force 

 is shown by the swiftness of motion of the ball. 



Force, then, is the name which we give to that 

 which causes' or, in the case of pressure, tends to 

 cause, motion. The force of gravity therefore means 



