158 GREAT MEN OF SCIENCE 



of conductors; and he observed that this also is a consequence 

 of the inverse square law, and can only be true if the latter 

 holds exactly. Every other law would lead to the existence 

 of forces in the interior of conductors, which would set the 

 electricity in motion and change the distribution, a fact which 

 already follows from Newton's consideration of gravitation. 

 He also shows the connection between the distribution of 

 electricity upon, and the curvature of, the surface of a con- 

 ductor, and the resulting phenomena exhibited by sharp 

 points. 



It should be noted that Coulomb had a forerunner in 

 Cavendish as regards the recognition of the fact that the 

 inverse square law of electric force can be deduced from 

 the confinement of electricity to the surface of bodies; 

 Cavendish's observation and considerations on this point, 

 which dated from 1773, had however remained unpublished, 

 and were only discovered much later among his posthumous 

 papers.^ 



LUIGI GALVANI {1737-1789) 

 ALLESSANDRO VOLTA {1745-1827) 



No sooner had Coulomb rendered the phenomena of 

 stationary electricity comprehensible in a manner for the 

 moment sufficiently satisfactory, than the entirely un- 

 expected discoveries of Galvani and Volta opened up quite 

 new prospects. A fresh source of electricity had been found, 

 which supplied a much more plentiful flow than those 

 hitherto known, friction and influence. Volta's pile took 

 the place of the electrical machine. A new appliance for 

 obtaining hitherto undreamed of knowledge was given us; it 

 became possible to study also the phenomena of flowing 



1 See p. 146 above. 



