196-198] Stresses in Dielectric Media 173 



Stresses in Dielectric Media. 



198. Replacing p by its value, as given by Laplace's equation, we obtain 

 equation (117) in the form 



o ) 



STT dx 



+ 2 - (K } + K - f V 



dx dx \ dx J dx\dx) 



+ 2 |(jr^) + *:i(^) i 



+2 ^ 8 ^ 8F ) + ^i( 8 /y 



ox oz \ oz J dx \ dz / 

 9 



If we put 



(119), 



^TT ox oy 



this becomes 



Let us suppose that a medium is subjected to a system of internal 

 stresses P xx , P xy) etc. ; and let it be found that a system of body forces 

 of components E', H', Z' is just sufficient to keep the medium at rest 

 when under the action of these stresses. Then from equation (79) we 

 must have 



x H ~af + ~d/j ' 



