116 
Prof. 1). J. Kortevreg on a General Theorem of 
Bu 
'Bt 
Bx 
Sv 
PoJ-^ 
0, 
Sv _ 2 , B(Y P + p) 
(10) 
"Along the boundary, 
da ov _ bw _ n 
8t = 8l~~8i 
• (11) 
" By means of these relations we have to prove that ~ 
constantly negative. 
BA . 
is 
" X. 
virtue of (5), 
BA 
St 
^JlKSx' SxSt + 8y' SySt + Bz ' BzBt) 
(Bv B 2 v Bv B 2 v Bv B' 2 v \ 
Bx Bx Bt By By Bt Bz Bz Bt) 
(8w B 2 iv Bw 8 2 iv Bw B 2 u- \-i 
c^'J78t + By-'8y-8i + Jz- BzTt)] dx ^ dz 
f 17*? *V S ^ 8»*\ , /&i &A/ 8 2 u B-ir \ 
2/ \ ' l\Sy B:J \by Bt Bz Bt) \8z Bu- )\8z8t~ BxTt) 
+ (j£ ~ ^)(&5 ~ W&A dX dy dZ ' 
" Applying the theorem of Green to the first term of the 
right-hand side of this equation, we get 
xm 
-4(s^ 
. Bv „„ Biv „«, \ , , , 
^r yhcjdxdydz. 
_i8t' v St v ' Bt 
" With respect to (10), this may be written 
the second term of which expression vanishes after partial 
integration by virtue of the equation of continuity. 
"As for the second term of the right-hand side of (12), 
effecting the multiplications and applying partial integration, 
