on various Ph^enomena of Induction. 269 



the thermo-electric rheometer was closed. That of one of the 

 inductor wires was also closed by plunging its two extremities 

 into a capsule full of mercury. Lastly, the other inductor wire 

 was put into communication with a pile of two elements, either 

 directly or by the intermediation of the brass wire No. 2, the 

 length of which had been made variable. 



12. Repeated experiments have shown, that for the addi- 

 tional lengths ofwiie increasing in'geometrical progression, the 

 intensities of the induced current, measured by the rheometer, 

 diminish in arithmetical progression («). 



13. The same trials have been repeated by opening the cir- 

 cuit of the second inductor wire, all other circumstances re- 

 maining constant. Their results have been as follows : — 



a. For the additional lengths of wire increasing in geome- 

 trical progression, the intensities of the induced current, mea- 

 sured by the rheometer, again diminisli in arithmetical pro- 

 gression (/3). 



b. The intensity of the induced current measured by the 

 rheometer is greater when the circuit of the second inductor 

 is closed than when it is open (y). 



c. From the existence of the laws (a) and (/3) it results that 

 for the lengths of additional wire increasing in geometrical 

 progression, the differences of intensity of the induced current, 

 measured by the rheometer, when the circuit of the second 

 inductor wire is closed and when it is open, decrease accord- 

 ing to an arithmetical progression (8). 



14. Let M be the intensity of the induced current measured 

 by the rheometer (general term of the arithmetical progres- 

 sion) ; 



T the corresponding term of the geometrical progression ; 

 a the first term of the arithmetical progression ; 

 e the first term of the geometrical progression (onit of the 

 additional length of wire) ; 



r ratio of arithmetical progression ; 

 q ratio of geometrical progression. 

 These quantities are connected by the relations 



15. The following Tables will serve as a proof of these 

 enunciations. The ratio of arithmetical progression has been 

 designated by r. 



