242 Mr. A. W. Flux on the 



Also the coordinates of B / are : — 



and those of B are : — 



f l5 77x being given in (viii.). 



The difference of path (measured in air) of the two rays, at 

 Fis 



~L 6 " C J~« — * — 1 &+6+,] 



+ " (<*-?) 



^ (d_?t+l) 7 (d_?) 



+ ?«'+y-/* (d _ n + i^! (r _ gi) . 



Now 



— = — n + znd order terms, 



>w 



ft* 

 and 



& + CH-1 = 2 [r*-i + </) A 2 ]=r^ 2 -(2/i-l)— — — ; 



i. e. is of the 2nd order, and therefore we need not calculate 



,, a , ' . lh + mmh—l 

 tne 2nd order terms m . 



Evaluating the other terms by means of equations (iv.) 

 (v.) (vi.) (ix.), we obtain the following result : — 



, u* + v 2 tuV — Iccu + Bv^ + v 2 



&k=ky + &- T 



r fMjy' r r 



- $? [2(» 2 + ««) (?-«0 + 2 (^) 2 (?-S a ) - =*±*V + *)] 



as given bv Herr Gumlich in Wiedemann's Annalen, xxvi. 

 p. 361. 



