Prof. E. P. Adams on Electrost Action. 897 



By means of (4) we find the normal traction at a surface 

 separating two dielectrics to be 



F __CK-g 1 )S 2 fK'-S,)S" 

 8irr* + Snr 2 



The surface conditions then give 



l67r(A. + 2/A) (. * J ^ «7T «7T 



V ^ ; 167ra 2 (X + 2 M ) A<? ' 



and the condition that there be no longitudinal traction 



gives 



SU-f-g 2 )<T 

 $7ra" 2 E 



It has been assumed that the solid tube is so thin that terms 

 in dja may be neglected, d being, as before, the thickness of 

 the solid tube. Substituting the value of S already given 



vK»ra 1 + s,) g 



d — s- • ( 18 ) 



>7ra 2 E I (K'- K) - + K log <?// j 



If, as in Prof. Morels experiments, K = K f 



»7r^a 2 (log^//) s 



(19) 



3. Increase in Internal Volume of a Charged Spherical 

 Condenser. 



The solution of this problem differs from that of the 

 cylinder in that it may be obtained exactly. For an in- 

 finitely thin spherical shell Pockels* gives the solution 

 obtained by means of the general equations of equilibrium 

 of an elastic solid. For the following it will be useful to 

 to have an expression carried to one degree higher of ap- 

 proximation, keeping terms of the first power in dja. The 



* L. c. Art. 5. 



