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. 

 Tiraraerman, has suggested a name for this quantity which 

 seems to me very satisfactory. It is perviahility. 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 perviahility 

 fx were of infinite extent, the capacity of the sphere would be 

 H Y^ and the resistance of space to the lines of induction would 



be -. 



4 7r/zro 



This result is readily reached by direct integration. The 



resistance of a shell bounded by surfaces concentric with the 



sphere is 



dr 



^^~4rr;,r2 (2) 



which integrated between r^ and oo gives for the resistance 



1 



R 



4^//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 =A(± _ i.) 



The number of lines of induction is [jl rFdS=47rQ. 

 Hence applying Ohm's law 



...R = L_(±_M 



4 ^/^ To ri/ (4; 



