266 M. W. Weber on the Measurement of Electric 



In the last column here and in the upper Table are given the 

 different values of e which were obtained for the Neumann's 

 induction-constant by adhering to the measure chosen by Kirch- 

 hoff, but using the different kinds of copper which have been 

 mentioned. Adhering, however, to the absolute measure hxed 

 as above, C'=C, W'=W, and e has always the value 2. 



§ 7. On the constants of the electric laws which depend on the 

 choice of measures. 



The law of induced currents propounded by Neumann represents 

 the intensity of these currents as dependent on a constant the 

 value of which must be determined from the measures according 

 to which the magnitudes taken into consideration are to be deter- 

 mined. This constant Neumann has called the induction-constant. 

 Such a constant occurs in the general expression of any natural 

 law which states how one magnitude is determined by another. 

 I may here give a summary of these constants for all the funda- 

 mental laws which refer to electromotive force, intensity, and 

 electric resistance. Each of these laws represents the desired 

 magnitude as an expression of other measurable magnitudes, 

 which has a constant as a factor the value of which is to be de- 

 termined from the measures chosen. 



1 . The fundamental law of the voltaic circuit represents the 

 intensity of the current i as an expression of the electromotive 

 force e, and of the resistance w ; for, if the constant whose value 

 is to be determined is called a, 



e 



i = ol • — 

 w 



This constant a has the following meaning. If J, E, W are the 

 absolute measures fixed as above for intensities, electromotive 

 forces, and resistance ; and if J', E', W' are the measures actually 

 used, we have 



JEW 

 "-J'E'W'' 



Hence using the absolute measure itself, a = l. 



2. The fundamental law of electro-magnetism represents the 

 electromotive force F as an expression of the quantity of mag- 

 netic fluid fjb, of the length ds, and of the intensity i of the ele- 

 ment, of their distance from one another r, and of a number which 

 is given by the angle (/> which r makes with ds ; that is, if the 

 constant whose value is to be determined from the measures 

 chosen is /?, 



F=/3.^ S in«£. 



rr T 



The constant has the following signification : — If P is the 



