ELECTROMAGNETIC THEORY 17 



itself a vector with the Cartesian components 



lE-H^. = EyH,-E.Hy, 

 [_E-H^y = EzHx — ExHz, 



\_E-H}2 = ExHy — EyHx. 



The symbol V^ denotes, in Cartesian coordinates, the operator 



dx- dy'^ dz^ 



V^ = — , + — , + 772 



