( 548 ) 

 t'^rom these three last equations we derive directly with the aid 



of (IV) : 

 (a). 



i»- -7^-^----ri^ = QM--- j-.-^. • • (n 



whilst 



We can easily show that one of the equations (F) is dependent 

 on the two others, as is clear. 



If we divide both members of ( V,'t) by iC- and if we add ( V,b), 

 we find : 



dz 2v du 



dri Qi{v—uy dri 

 From (7 V,a) follows : 



du dz dv dz _ ^'^ _ _ X f'^llZ]^\ Q dz dz^ 



dn'di~dl'd~yi~^''~''^dïd^l~^''~~''\ uv j2iTi'd~ri' 



By substituting here — we find : 



dz 2u dv 



dS, Q^{o-^l}' d§ 



We can now write down out of (///) the following set of equations: 



{VI) 



So, as soon as u and ^' are known, the problem will be solved. 



