54 



BELL SYSTEM TECHNICAL JOURNAL 



As the velocity of a light ray of unit current vector j is given by 



jck-'j = ^ (16.9) 



We can, by (18.2) and (16.9), compute the change in the velocity caused 

 by the stress, if we know the constants tt. 



Altering (18.1) to aK~ = aK~ + aTa.~ aX we see that: 



K~" = K~'° + t'X' where tt' = 



(18.3) 



The alteration of K can be expressed as a function of the strain by 

 substituting ce for X in (18.1). 



i^-i = K~'° + Tree = A'~'° + me (18.4) 



m — TTC, T = ms (18.5) 



Operating in (18.4) as we did on (18.1) we find m transforms as 



m' — amac (18.6) 



Applying the crystal symmetry operation to these matrices shows that 

 they reduce to the following 



Triclinic system 

 36 constants 



TTil Xl2 TTis 7ri4 TTis TTie 



X21 7r22 7r23 7r24 7r25 7r26 



TTsi 7r32 TTss TTu TTss TTse 



7r4l 7r42 7r43 7r44 7r45 7r46 



TTsi 7r52 7r53 7r54 TTss TTse 



TTei 7r62 7r63 7r64 TTes TTee 



The m matrix 

 is entirely 

 analogous 



(18.7) 



Monoclinic system 

 .V3 is binary 

 20 constants 



Orthorhombic 

 system .T3 

 is binary 

 12 constants 



TTii 7ri2 Xi3 TTie 



7r21 7r22 7r23 X26 



TTsi 7r32 7r33 T36 



7r44 X45 



7r64 X55 



Tei 7r62 TTes xee 



TTll TTlo 7ri3 



■T21 7r22 7r23 



TTsi 7r32 7r33 



7r44 



TTSB 



Tree 



The m matrix 

 is entirely 

 analogous 



(18.8) 



The m matrix 

 is entirely 

 analogous 

 (Rochelle salt) 

 (18.9) 



