134 MR. GWYTHEB ON THE LAGBANGIAN FORM OP 



O TT ^<'' 



d(p. 



therefore 





I I da- 





or 





«_6?<r 





^*H-%^ • • • 





whence we obtain 





da da 



f/tr 



df^ 



= V^J^t g + VfJ^t g + V?>jD, ^. . 



Now 





y. « +V^ ^+V^. 7^S(v^.a + V?>./3 + 



yiiil 



V-PiH + V-PzH + V?? jj jj 





V(v<p.a + v^,/3 + v<Pj7) 





(6) 



(7) 



H 



of which the vector part is seen to vanish and the scalar 

 becomes —3, whence 



VfxT)^g+Vf.D.g+V<P5D,^=-D,V<p.^-D^V<Pzg 



