SECT. XXVIII. DISTRIBUTION. 287 



to the distance of the globe. A comparison of the number of 

 oscillations performed in a given time at different distances will 

 determine the law of the variation of the electrical intensity, in 

 the same manner that the force of gravitation is measured by 

 the oscillations of the pendulum. Coulomb invented an instru- 

 ment which balances the forces in question by the force of the 

 torsion of a thread, which consequently measures the intensity ; 

 and Sir William Snow Harris has constructed an instrument 

 with which he has measured the intensity of the electrical 

 force in terms of the weight requisite to balance it. By 

 these methods it has been found that the intensity of electrical 

 attraction and repulsion varies inversely as the square of the 

 distance. However, the law of repulsive force is liable to great 

 disturbances from inductive action, which Sir William Snow 

 Harris has found to exist not only between a charged and 

 neutral body, but also between bodies similarly charged ; and 

 that, in the latter case, the inductive process may be indefinitely 

 modified by the various circumstances of the quantity and 

 intensity of the electricity and the distance between the charged 

 bodies. 



The quantity of electricity bodies are capable of receiving 

 does not follow the proportion of their bulk, but depends 

 principally upon the form and extent of their surface. It 

 appears from the experiments of Sir W. S. Harris that a 

 given quantity of electricity, divided between two perfectly 

 equal and similar bodies, exerts upon external bodies only one 

 fourth of the attractive force apparent when disposed upon one 

 of them ; and if it be distributed among three equal and similar 

 bodies, the force is one ninth of that apparent when it is 

 disposed on one of them. Hence, if the quantity of electricity 

 be the same, the force varies inversely as the square of the 

 surface on which .it is disposed ; and if the surface be the same, 

 the force varies directly as the square of the quantity of 

 electricity. These laws however do not hold when the form of 

 the surface is changed. A given quantity of electricity disposed 

 on a given surface has the greatest intensity when the surface 

 has a circular form, and the least intensity when the surface is 

 expanded into an indefinite straight line. The decrease of 

 intensity seems to arise from some peculiar arrangement of the 

 electricity depending on the extension of the surface. It is 



