54 



Proceedings of the Royal Irish Academy. 



IX. — It will be seen that the step-like form of the curves is again 

 well defined. In this, as in all the "charge" methods, the "rounding off" 



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of the steps is such as to make them concave upwards, unlike the convex 

 form exhibited in the " visual " experiments. It was not possible to push 



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the observations below the fourth or fifth step, and for that reason a third 

 " charge " method was devised, which enabled us to trace the curve right 



