224 



On a Magneto-electric Phenomenon. 



meter. The current from a Daniell cell was sent through the 

 suspended coil and measured. In the fourth column of the 

 following Table will be found the deflection of the coil due to 

 currents tabulated in columns 2 and 3. In the fifth column 

 is the deflection due to the residual magnetism; and in the 

 sixth column the strength of field in absolute units, calculated 

 from the formula 



H== 



3-73 



x deflection in degrees 



deflecting current in absolute units x cos 8 



Table IV. 



Number of 

 cells. 



Magnetizing 

 current, in 

 amperes. 



Deflecting 

 current, in 

 amperes. 



Deflection 

 = 8. 



Deflection 

 due to 

 residual 



magnetism. 



Calculated 



field, in 



absolute 



units. 



10 



11-92 



•514 



65 



4 



11,200 



9 



1105 



•530* 



64 



4 



10,260 



8 



1052 



•502 



63 



4 



10,320 



7 



9-48 



•496 



62-5 



4 



10,150 



6 



8-63 



•480 



61-5 



4 



10,050 



5 



7-60 



•480 



60-3 



4 



9,470 



4 



6-45 



•480 



59 



4 



8,930 



3 



5-14 



•480 



57 



4 



8,120 



2 



3-67 



•480 



51-5 



4 



6,470 



1 



1-98 



•480 



40-5 



4-5 



4,140 



* Obviously over-estimated, hence small results. 



The residual magnetism was always the same till one cell only 

 had been employed to excite the electromagnet, when the 

 deflection was clearly greater. This I repeated several times 

 with one and with more than one cell : a deflection of 4^° 

 was always obtained from one cell, and of 4° from more than 

 one cell. To obtain a still higher residual magnetic effect, I 

 drew the terminal along a fine wire and gradually diminished 

 the field ; by this means I obtained a residual field giving a 

 deflection of 5°'4. The magnetic fields corresponding to 

 the deflections 4, 4J, and 5*4 are 312, 352, and 422 absolute 

 units. 



Fig. 3 shows the field-intensity measured by the two 

 methods. They do not agree, nor are they quite proportional, 

 nevertheless they are of the same order of magnitude. The 

 discrepancy is greater than would be expected from errors of 

 an experimental kind, even though the apparatus was hastily 



