430 POPULAR LECTURES AND ADDRESSES. 



the concluding experiment which crowned Caven- 

 dish's theory. Faraday found by the most 

 thoroughly searching investigation that the elec- 

 trical force in the circumstances supposed was zero, 

 and supplied the minor proposition of Cavendish's 

 syllogism. Therefore the law of electrostatic 

 force varies with the inverse square of the 

 distance. This result was obtained with far less 

 searching accuracy by Coulomb and Robinson, 

 because their method did not admit of the same 

 searching accuracy. On this law is founded the whole 

 system of electrostatic measurement in absolute 

 measure. Mathematical theory lays down the pro- 

 per electrostatic unit that quantity of electricity 

 which, if a quantity equal to it is possessed by each 

 of two bodies, those two bodies act and react 

 upon one another with unit force at unit distance. 

 On this is founded the system of absolute 

 measurement in electrostatics. 



Cavendish's other experiments, and series of 

 experiments because I believe Professor Clerk 

 Maxwell is to edit a whole series of experiments 

 measuring electrostatic quantities led to the 



