Brard 
Py = dr, .( Vv 
Pee Bs 
where dQ, is the intensity of the vortex ribbon Lr. 
According to (5.18), it is seen that 
iia —_ 
cc gh: (5-20) 
Let Bf , By? be the points derived from B, B' by the trans- 
lation "+ = 7; (B) and Vrs se BY those derived from B, B' 
by the translation - + n, (B). Let ry denote the surface whose 
edge is the contour By, M;, M}, By and ye the surface whose 
edge is the contour Bf, By* f it : Siri ay let pals be the 
surface bounded by the contour e, fit, aya BY, and “177 the 
surface bounded by the contour M, Mi! By Be , Sy the aa ohare 
bounded by the contour Cr, and S, the Paeice bounded by the contour 
es _sthe surtace 
¢ , , , 
S. +2, ay ei se w2e 
—> 
is closed and the flux of = through this surface is null. As it 
is equal to+ (dT, +dI,- Is) if We Fe = +2 andto = (dh + dT oc 
- dT) if ve tT, =, - 1, we Haye 
df o£ dF = aE (5.21) 
To. ZS TS ae ee eo ae 
1218 
