166 Adams — Electromagnetic Effects of 



Below are given the successive equilibrium positions of the 

 needle in six series of reversals, as an illustration of the results 

 that have been obtained : 



No. 1. 



No. 



2. 



No. 3. 



63 





165 



130 



60 m 



172 



178 



109 122 



64 76 



188 



223 



122 130 



71 79 



200 



220 



112 130 



69 76 



213 





121 140 



69 







146 156 

 164 171 

 162 



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

 giving: 



d — 22-47 

 d'= 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 deflections 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. It is evident that with variations such as are present 

 here the measurements can be regarded only as a rough 

 approximation. But the most important fact to be observed is 

 that when the spheres directly under the magnetometer are 

 changed from negative to positive a deflection toward the 

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

 positive to negative a reverse deflection takes place. • When on 

 account of changes in the zero-point some of the deflections do 

 not apparently follow this rule, they are entered with a nega- 

 tive sign in finding the average deflection. There has invari- 

 ably resulted a positive deflection 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 



