138 Prof. Thomson & Mr M e Clelland, On the Leakage of [Mar. 9, 



These results are plotted in the curve shown in Fig. 8, where 

 the ordinates are proportional to the square roots, times of leak 



Fig. 8. 



and the abscissas proportional to the distances of the centre of the 

 discs from D. The observations are represented by a straight line 

 cutting the horizontal axis at a point corresponding to a point in 

 the tube about 4 centimetres behind D, and this point is approxi- 

 mately on the flat j)late A and thus in this case as in the preced- 

 ing, the rate of leak varies inversely as the square of the distance 

 from the flat plate. Thus reversing the electrodes has produced 

 no change of the place of origin of the Rontgen rays. 



The origin of these rays in these tubes seems to be the flat 

 plate, though when this is made the positive electrode the origin 

 seems slightly displaced. To test this point a set of experiments 

 were made with a tube whose shape and dimensions are shown in 

 Fig. 9. In the experiments made with this tube the plate was the 



Fm. 9. 



positive and the wire the negative electrode. The following results 



were obtained. 



Distance of centre of discs from A. Time required to leak 50 scale divisions. 



5 5 



10 145 



15 23 



20 34 



25 445 



30 65 



