20 ESSAYS AND OBSERVATIONS- 



ving a body in motion, mud be an ope- 

 ration of a different kind, from that of 

 preferving it at reft. 



In order to handle this fubjeft with 

 fome degree of accuracy, I fhall endea- 

 vour to make out the three foUoNA^ing 

 propofitions : Firfiy That motion is a 

 continued aclion, which mufl: infer fome 

 power^ continually acting. Secondly^ 

 That as matter refifls a change from reft 

 to motion, as well as from motion to reil:» 

 this reliftance is not to be accounted foi; 

 by the mere negation of a caule, but is a 

 pofitive efFedl to require a caufe as much 

 as motion does. /^nd, /^A', after ex- 

 plaining the caufe of the continuance of 

 motion, I fliall endeavour to fliow, that 

 it is an effedt of a different kiiid from 

 the reliftance which matter exerts againfl 

 any impulfe which puts it in motion. 



With regard to the firit propofidon, 

 motion evidently differs from the other 

 properties of matter. It is not like ex- 

 tenfion, figure, and fuch like qualities 

 effential to matter. Every body muft be 

 of a certain fize and figure ; but it is ea- 



