110 Trans. Acad. Sci. of St. Louis. 



to treat the quantity which Faraday called specific inductive 

 capacity as a specific conducting power for lines of induction. 

 It is a quantity analogous to what is called permeability 

 of a medium for magnetic lines. My former assistant, Mr. 

 Timraerman, has suggested a name for this quantity which 

 seems to me very satisfactory. It is perviability. For 

 electrostatic conduction of any tube of induction as ex- 

 pressed by equation (3) which follows, he suggests the 

 name perviance as meaning electrostatic conductance in the 

 field of an electrical system. If the medium of perviability 

 [^ were of infinite extent, the capacity of the sphere would be 

 [1 v^ and the resistance of space to the lines of induction would 



1 



be -. 



This result is readily reached by direct integration. The 



resistance of a shell bounded by surfaces concentric with the 



sphere is 



dr 



^^~4x^r2 . (2) 



which integrated between r^ and oo gives for the resistance 



1 



R = 



4:r^r, (3) 



If the sphere be surrounded by a concentric spherical and 

 conducting shell, forming a condenser, the difference of 

 potential between the acting surfaces will be 



v-Q 





The number of lines of induction is// I FdS=47rQ. 

 Hence applying Ohm's law ' 



^ IX \i\ r 1 / R 



.•.E = ;j 1 ... 



