34 LECTURE L 



the most part presents itself to our notice, 

 and is cognizable by the eye and touch, we 

 know that it has a property called by Sir 

 Isaac Newton vis inertice, an indisposition 

 to move unless impelled to motion, and a 

 disposition to continue in motion unless re- 

 tarded. 



There are some philosophers who think, 

 that properties similar to those of the a;g- 

 gregate mass, likewise belong to every atom 

 of which it is composed ; whilst others, on 

 the contrary, think, that the atoms have very 

 diiFerent qualities, and that the vis inertice is 

 the property only of the aggregate mass. 

 The matter of animals and vegetables is, 

 however, an aggregate mass ; it is as we ex- 

 press it, common matter, it is inert ; so 

 that the necessity of supposing the superad- 

 dition of some subtile and mobile substance 

 is apparent. 



Taking it for granted that the opinions 

 generally entertained concerning the cause 

 of electrical motions are true, analogy 

 would induce us to suppose, that similar 

 motions might be produced, by similar 



