218 Experimental Philosophy. [Lecture 15. 



from the steeple of Westminster Abbey, having, 

 by the power of gravity, once acquired a certain 

 degree of motion, would continue to fall, by the 

 motion it had received by the first impulse, even 

 if the cause were to cease. For instance, if when 

 it had fallen halfway it were possible to deprive 

 it of gravity, it would still, by the above law, 

 continue its motion, and in the direction in which 

 it was sent, as a stone continues to proceed, when 

 thrown by the hand, without any new impulse. 

 The power of gravity, however, does not cease, 

 and therefore every inch the bullet falls it re- 

 ceives an increase of motion. Thus, if in the 

 space of one second it falls one pole (sixteen feet 

 and a half), it will then have acquired as much 

 swiftness or velocity as will carry it through three 

 poles in the next second, through five in the 

 third, through seven in the fourth, and nine in 

 the fifth. This. will account for its accelerated 

 motion, and for the increased force with which 

 it falls near the bottom. Thus the time which 

 bodies take in falling is easily calculated ; for, if 

 they fall about one pole in the first second, 

 which is what they nearly do by the force of 

 gravity, they will then fall three in the next, and 

 in five seconds they will fall about twenty-five 

 poles, or three hundred feet. These spaces, how- 

 ever, are a little diminished by the resistance of 

 the air. 



As heavy bodies are uniformly accelerated in 

 their descent, they are as uniformly retarded by 



