Intelligence and Miscellaneous Articles. 



85 



to the actual rate of variation of the ' force-function ' by the dif- 

 ferential coefficients of which the mutual action between the magnet 

 and the wire would be represented if the intensity of the current 

 in the wire were unity." 



This investigation was undertaken to ascertain if the laws of 

 derived circuits apply to the currents of induction, which are re- 

 presented by equations of which the above is a type. A reflecting 

 galvanometer of large resistance was included in the secondary 

 circuit, and connected by copper, wires of very small resistance with 

 the coil in which the secondary currents were produced : the re- 

 sistance of these wires was infinitesimal in comparison with the 

 resistance of the galvanometer. The galvanometer- was then 

 shunted. The first two columns of the following Table show that, 

 with an inappreciable resistance outside of the galvanometer coils, 

 the shunts made no difference in the deflection of the galvanometer- 

 needle when the shunts were not less than three ohms. Below this 

 the current divided. The resistance of the galvanometer was 5880 

 ohms ; and the last numbers in the second and third columns show 

 that an equal impulse was transmitted through both the shunt and 



Exterior 



Shunts, 

 in ohms. 





Exterior 





Eesistances, 



Deflections. 



Eesistances, 



Deflections. 



in ohms. 





in ohms. 









3 



210 



10 



210 







4 



210 



20 



210 



o • 



5 



210 



30 



210 







6 



210 



40 



210 







5880 



210 



100 



190 



the galvanometer ; for no reason can be assigned why it should take 

 one course in preference to the other. Two galvanometers, there- 

 fore, of the same resistance, one forming the shunt to the other* 

 will give the same deflection, which is equal to that given by the 

 undivided circuit. 



Eesistances were then introduced into the circuit exterior to the 

 galvanometer-coils, and a shunt of 588 ohms was used. 



The fifth column shows that no effect was produced by the 

 shunt until the exterior resistance was appreciable in comparison 

 with that of the galvanometer. 



The following Table exhibits the effect of resistances which were 

 appreciable in comparison with the galvanometer-resistance. The 

 same shunt of 588 ohms was used. The second column is calcu- 

 lated on the assumption that *=-t- (where h l is a coefficient) is 



equivalent to \—-q, and that the laws of Kirchhoff hold. The 



third column is obtained from the experimental data. The fourth 



E 



and fifth columns are also calculated on the assumption that i=^ 



XI 



