PHYSICAL AND LITERARY. Sj 



fities of matter, if they are inert at all, 

 piufl have equal inertiifj or require equal 

 forces to move them with equal velocities* 

 And, in every cafe, the inertia is propor- 

 tional to the quantity of matter. 



If a body left at reft does not begin 

 motion of itfelf, it is determined to re- 

 main in that ftate, not fromi any real re- 

 pugnance to motion, which is as conform- 

 able to its nature as a ftate of reft, but 

 becaufe nothing is done without a caufe, 

 and, when adled upon by any external 

 influence, it obeys without reluctance j 

 the motion produced being in exacfl pro- 

 portion to the moving caufe. It has a 

 conftant fufceptibility of motion, and a 

 perfedl facility in receiving it. ^ But wc 

 may as well afk, why an inadtive fub- 

 ftance does not begin fome degree of mo- 

 tion of itfelf? as, why different powers 

 are requifite to produce different moti- 

 ons ? When people talk of the reftftance 

 of matter at reft, as of an a^ive poijuer, 

 ftruggling againft any agent, and adive- 

 Jy oppofing it, they furely frame to them- 

 felves fome notion of force antecedent to 



all 



