Electromagnetic Theory of Light. 87 



^{|-| +K |</ AK -)- K i^ K - I )}= K 

 ^{|-| +K £^ K -')- K |( MK ">} = K 



It' 



K25) 





%, 



(27) 



-S+^^-^^(^>^i [ - (26) 



By differentiation of the first equation of (26) and substi- 

 tution from (25), we get, having regard to 



df + dg + dh^ 

 dx dy dz ' 

 which is a consequence of (1), (3), (7), 



or, remembering that the functions as dependent upon time 



vary as e l 



vy + *y + K(A 2 + .Q(/AK-o 



-Kg^^AK-O-K 



(&z?cte 



(AAK- 1 ) 



+ ^|(^-.)-¥l^^= ' ( 28 > 



with two similar equations in g and h. 



Introducing now the expansion in powers of AK and A/4, 

 we get as the first approximation 



VV. + ^-K^CAoAK-')- t|5 | (W-) = 0, 



