54 



Proceedings of the Royal Irish Academy. 



and method of application of the transverse electric field required to produce 

 the increase of conductivity. 



In the first place, we tested the effect of repeated applications and 

 removals of the field. It was found that after a number of applications 

 and removals the conductivity reached a maximum, and further applications 

 produced no further increase. The number of applications required to 

 produce the maximum effect depended on the electric field used and to some 

 extent on the nature of the layer. 



Minutes 



The intensity of transverse field required to produce the effect was 

 investigated. A layer was formed, and its conductivity measured ; a small 

 transverse field was then applied and removed a sufficient number of times 

 to produce the maximum effect and the conductivity again measured. A 

 larger field was then applied and removed in the same way, and so on, the 

 conductivity current between the tinfoil terminals being always that given 

 by an E.M.F. of 2 volts. Curves A and B (fig. 4) were plotted in this way 

 for two layers, one of which A had a thickness of paraffin beneath the powder 

 layer of 105 mms., and the other B a thickness of 219 mms. The ordinates 

 show the ratio of the increased conductivity to the original conductivity and 

 the abscissae the transverse voltage. Even small voltages produce an effect, 



