COEFFICIENTS OF SOLENOIDS. 



§ 25. The formulae above deduced do not apply to solenoids 

 wound with wires or strips, inasmuch as the calculation is based 

 on the supposition that the solenoid forms a cylindrical current 

 sheet. In the practical problem, we have to take into account 

 the thickness of the w^ire and of the insulation, for which it will 

 be necessary to add small corrections to the numbers which are 

 obtained from the tables already given. Important formulae as 

 well as tables to meet such practical problems have been calculated 

 bv Kosa^^^ and Cohen^-^ 



(1) Eosa, Bull. Bur. Standards, 2, 161, 1906; 4, 369, 1908. 



(2) Cohen, Tull. Bur. Standards, 4, 183, 1908. 



