298 Mr. E. P. Adams on the Electromagnetic 



The needles were then moved a little closer to the spheres, 

 giving : 



d , 22-47 



cV 28-84 



A-B 1-834 



No. 4. No. 5. No. 6. 



92 



114 





164 



108 



84 



106 



135 



148 



156 



113 



118 



120 



135 



148 



149 



108 



155 



142 



149 



152 



143 



125 



135 



164 



192 



139 



147 



155 







In all these cases, the first column gives the readings when 

 the spheres directly under the magnetometer are positively 

 charged, and the second column when they are negatively 

 charged. In No. 1, the successive deflexions are : 3, 6, 2, 12, 

 5, 8, 10, 7, 7 ; giving an average of 6*7. In No. 4 they are : 

 21, 13, 0, 8, 18, 18, 9, 19, -6, 10, -8, 7, 9 ; giving an average 

 of 9*0. It is evident that with variations such as are present 

 here the measurements can be regarded only as a rough 

 approximation. Bat the most important fact to be observed 

 is that when the spheres directly under the magnetometer 

 are changed from negative to positive a deflexion towards 

 the small figures of the scale takes place ; and when changed 

 from positive to negative a reverse deflexion takes place. 

 When on account of changes in the zero-point some of the 

 deflexions do not apparently follow this rule they are entered 

 with a negative sign in finding the average deflexion. There 

 has invariably resulted a positive deflexion on taking the 

 average. 



Earlier experiments were made with four spheres in each 

 set. With this number it was possible to get much higher 

 speeds — 75-85 revolutions per second. Similar qualitative 

 results were observed, but when comparison with theory was 

 attempted it appeared that fair agreement could be obtained 

 if the maximum value of the magnetic force were used instead 

 of the average. This was largely an accidental result, a 

 sufficient number of reversals not having been made. 



It would have been desirable to have made a larger number 

 of reversals in each series, but after the apparatus had been 

 running for some time the bearings became so much heated 

 that it was impracticable. 



