NEUMANN'S FORMULA. 337 



The first term of the second member is null, being extended to 

 the closed contour C ; we have then 



f4V>= - fi-\**- f?LV 



J ^s V J r W J r 



and therefore 

 ( 34 ) 



This remarkable formula is due to F. E. Neumann. We deduce 

 from it for the value of the coefficient M (341), which expresses the 

 flow of force common to the two sheets, each supposed equal to unity, 



(35) 



