372 Mr Southerns, Experimental Investigation, etc. 



really made in view of this suggestion, but from the point of view 

 of energy it would appear difficult to explain the result in any such 

 way as this. For we may liken the metal surface to a series of 

 buckets which are filled with condensed air, when the surface is 

 charged positively, but empty when it is charged negativelj''. 

 Now if we have a number of such surfaces, fixed to spokes, 

 radiating from a central axis so as to form a kind of wheel (like 

 a water-wheel) and place this between charged field plates, we 

 should have all the buckets on one side full and those on the other 

 side empty, and the wheel would revolve. It is difficult to see 

 where the energy would be drawn from to keep up this rotation. 



It may be of interest, as a mere speculation, to see whether the 

 theory of gravitation which supposes that the attraction between 

 unlike charges is somewhat greater than the repulsion between 

 like charges, could be modified to suit the present results. Let us 

 suppose that the repulsion between two positive units at a given 

 distance apart is P, and that between two negative units N, and 

 that the attraction between a positive unit and a negative unit is 

 M. Then the attraction between a neutral body (containing a 

 unit of positive and a unit of negative electricity) and a positive 

 unit will be M — P, and that between the neutral body and a 

 negative unit M—N. The difference between these will be 

 N—P, which is the effect found in the experiments. Again the 

 attraction between two neutral bodies (each containing one positive 

 and one negative unit) will be 2M — (P + N) and this will be 

 ordinary gravity. The last expression is much smaller than N—P 

 and thus we should have the result that while N and P both differ 

 considerably from M, their mean is very nearly equal to M. Since 

 in the attraction M one charge of each kind is employed, it is 

 perhaps not unnatural to suppose that this might be the case. 

 The actual differences between M, N and P would of course be 

 exceedingly small in comparison with their absolute magnitudes. 

 Assuming M to be the ordinary electrostatic attraction, we have 

 two equations for finding iVand P. It should be remembered that 

 in the experiment, as in this theory, no lines of force pass between 

 the attracting masses. In the experiment the lines do not pass 

 to the earth, but sideways to the field plates. Turning aside from 

 such hasty speculations, the writer would be most grateful for 

 suggestions as to possible sources of error in the experiments, as he 

 hopes to have an opportunity of repeating them later with im- 

 proved apparatus, the design of which might be modified in view 

 of any suggestions thus made. 



In conclusion the writer desires to express his thanks to Sir J. 

 J. Thomson and to Professor W. M. Hicks and Dr S. R. Milner 

 for valuable criticisms and for the kindly interest which they have 

 taken in the experiments. 



