Medium separating Electrified Particles. 359 



1. When the distance between the particles is changed, 

 corresponding tubes of polarization in the two diagrams are 

 similar to one another. 



2. The equipotential surfaces in the two diagrams are also 

 similar to one another. If, however, the distance between 

 the particles changes from I to al, the eauipotential surface 



V 

 V changes to a similar surface, on which the potential is — . 



If, then, the n th line of force cuts the equipotential sur- 

 face V at the point x, y in the first diagram, the n th line will 



V 



cut the equipotential surface — at the point ax, ay in the 



second diagram. a 



Thus, in the case where M=12 and Z = 10 the coordinates 

 of the following intersections, among others, were found by 

 measurement on a carefully prepared diagram. 



Line of force. Equipotential surface. x. y. 



7 1 5-15 5 : 95 



7 4 5-35 2*28 



If the diagram were enlarged in the ratio of 4 to 1, the 

 coordinates of the point corresponding to the intersection 

 of 7 and 4 would be 4^ and 4j/ or 21*4 and 9*12. 



V 



The potential at this point would be V' = — = 1. 



Thus we have found the coordinates of the point of inter- 

 section of the line of force 7 and the equipotential surface 1, 

 when the distance between the particles is 40 centim. 



In the same way, and by means of the same original 

 diagram, the point of intersection can be found for a number 

 of other distances, and the path which it follows, when the 

 two particles approach one another, can be plotted as in fig. 1. 



In this figure the first of the numbers in brackets attached 

 to each curve gives the number of the equipotential surface, 

 and the second that of the intersectino; line of force. The 

 numbers along the curves show r the distance of the particles 

 from the centre of gravity, when the energy-cell is at the 

 point marked on the curve. 



It will be seen that the energy-cells move in more or less 

 parabolic curves towards the centre of gravity of the two 

 particles, and that during this process they are constantly 

 approaching the two particles ; so that, if these are not infi- 

 nitely small, energy must be constantly passing into them 

 from the sether. 



Maxwell has shown that in all cases the number of energy- 

 cells in the aether is twice the potential energy of the system. 

 So that, if we suppose each cell to contain half a unit of 



2 B 2 



