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E = jaz cdz =a l z (j. l z l^ ' -- , y jdz. 

 O o 



When now we introduce again : = z i^^ -, this quantity becomes: 



oo 

 



We may transform (III) also by putting: 



I) 



a 

 Then we get the equation : 



^-4, ^--' 



To this belong the boundary conditions: 



c = for 11 = 



c=C „ ^ = 



C = ,, Z ■= CO. 



Here again the solution will be independent of a and D viz.: 

 From this we find : 



Vb) 



Ez=(azcdzz=alzflz.y — ]dz = aFly — \. . (/ 







When now we compare the found values of E, (IV6) proves to 

 agree with (IVrï) only when: 



F(p) = A.p% 



where A is a constant. So E becomes: 



E = a A'^'-^ = Aa^kn'U>f'h {I Vc) 



aVs 



Of this result the fact that in the first place interests us is that 

 E proves to be proportional to y'/». 



To deduce from the acquired result what E becomes for a surface 

 of an arbitrary shape we imagine that this surface is divided into 

 narrow strips with the long sides jiarallel to the axis of // i. e. to 

 the current. As the breadth of these strips may not be taken too 

 small when we wish to apply the acquired results, but on the other 

 hand may not be too broad when we want to consider them as 



