C 189 ] 



XXVI. Electromagnetic and Calorimetric Absolute Measure- 

 ments: the Absolute Value of Siemens' s Unit of Resistance in 

 Electromagnetic Measure; the Relation between the Current- 

 work and the Heat-evolution in stationary Galvanic Currents ; 

 and the Absolute Values of some constant Hydroelectromotive 

 Forces in Electromagnetic Measure. ( Condensed Comparison 

 of the Results of a Series of Investigations?) By H. F. 

 Weber, Professor of Mathematical and Technical Physics 

 at the Federal Polytechnic Academy of Zurich. 



[Concluded from p. 139.] 



IV. Absolute Values of constant Hydroelectromotive Forces. 

 {Third Procedure for the absolute Determination of the 

 Siemens Unit of Resistance.) 



HAVING given in the foregoing the experimental proof 

 that the mechanical work consumed in the flow of sta- 

 tionary galvanic currents, when there is no other action of the 

 current, indeed finds its exact equivalent in the heat produced 

 by the current, a new path can be entered in order to deter- 

 mine the absolute values of galvanic resistances and constant 

 hydroelectromotive forces. 



I. Measure the quantity of heat Q, which is produced by 

 the current i (measured absolutely, according to any system 

 whatever) in a conductor whose resistance is w, which forms 

 part of a circuit, during the time z ; the absolute value of the 

 resistance w (measured according to the same system) is then 

 to be calculated from the equation 



JQ = i 2 wz. 



II. If the ratio of the resistance w to the sum of the resist- 

 ances w-i of the rest of the circuit be then ascertained by means 

 of an appropriate procedure, the heat produced in the entire 

 circuit by the constant current i during the time z will be ob- 

 tained in the expression 



s(Q)-(i+5). 



If E denotes the sum of all the electromotive forces of the cir- 

 cuit, according to Ohm's and Joule's laws, combined, 



JS(Q) = i 2 t(w)z = i~Ez 



holds good. For the absolute determination of the sum of the 

 electromotive forces in the circuit, or, more briefly, for the 



