4 OUTLINES OF NATURAL PHILOSOPHY. 



motion (47.), equal to the velocity multiplied 

 into the indefinitely small portion of time, during 

 which the motion is supposed uniform. Thus, if 

 S he the increment of the space, t the correspond- 

 ing increment of the time, and V the velocity* 

 S zi V t ; hence 



These formulae apply to motion of every kind, whether 

 accelerated or retarded, and express generally the re- 

 lation between the velocity, the increment of the 

 space, and the increment of the time. 



57. The quantity of motion in a moving body is 

 estimated by the product of the mass, or quantity 

 of matter, multiplied by the velocity. 



The quantities of motion in two bodies are the same, 

 when their velocities are inversely as their mas- 

 ses. 



If M and M' be the masses of two bodies, V and V 

 their velocities ; if M : M' : : V : V, the quantities 

 of motion are equal, for M x V = M' x V. 



58. When 



