454 



Messrs. Guthrie and Boys on 



first experiment made. Then the disk was raised 1 millim. by 

 means of the graduated rod r for each succeeding experiment. 



The ebonite disk and central clamp had been found to be 

 unaffected by the fastest speed used. In order to avoid ex- 

 travagant torsion, the rate of rotation was made less when the 

 distance was small. 



In Table II., column D shows the distance in millimetres 

 between the upper surface of the magnet and lower surface of 

 the copper disk ; A shows the observed angles of depression ; 

 T shows the time in seconds for one revolution of the worm- 

 wheel ; A' is the product of A and T. Since T is inversely 

 and A is directly as the rate, A / shows the pure effect of 

 distance; it would be a constant if the distance did not vary. 

 Each of the experimental numbers given, whether of angle or 

 time, is the mean of never less than three observations. These 

 observations of angle and time were simultaneous. 



Table II. 



D. 



A. 



T. 



A' = AXT. ; 



1 



106-8 



137 



1463-2 



2 



78-0 



13-7 



1068-8 



3 



75-6 



102 



771-1 1 



4 



57-0 



101 



575-7 1 



5 



683 



65 



443-9 



6 



50-9 



72 



366-5 j 



7 



55-1 



53 



292-0 j 



8 



43-3 



5-3 



229-5 1 



9 



36 3 



5-3 



192-4 j 



10 



f 451 

 \44-6 



J 36 

 \36 



/ 162-4 1 

 1 160-6 | 



11 



361 



3-7 



133-6 



12 



30-5 



37 



112-8 



18 



25-6 



35 



96-6 



14 



210 



3-6 



' 75-6 



15 



J 7-9 



34 



60-9 



16 



15-5 



35 



54-25 



17 



13-3 



36 



47-88 



18 



11-6 



35 



4060 



19 



10-4 



35 



36-40 



20 



f 9-0 

 1100 



J 3-5 



[3-6 



f 31-50 



1 36-00 



21 



80 



35 



28-00 



22 



71 



35 



24-85 



23 



6-2 



35 



21-70 



24 



52 



3-5 



18-20 



25 



4-8 



34 



16-32 



26 



46 



3-4 



15-64 



27 



35 



36 



12-60 



28 



35 



36 



12-60 



29 



30 



36 



10-80 



30 



2-6 



36 



9-36 



The second numbers opposite distances 10 and 20 millims. 



