132 POPULAR LECTURES AND ADDRESSES. 



Lastly, as to the objects to be aimed at in 

 respect to the use of this great system of units. 

 Nothing can be much more satisfactory than is 

 the measurement of somewhat large resistances, as 

 we have it habitually as present ; but if we want 

 a better method for low resistances, we will 

 be helped very much by the use of the mho 

 boxes of conductivities which I have indicated. 

 The great thing we want now in the way of 

 practical electric measurement is a good standard 

 of electromotive force. That was the chief object 

 of a recent British Association Committee, but 

 it has not yet been satisfactorily attained for 

 practical purposes. Standard cells serve for the 

 purpose to some extent, but we want something 

 better, something of the nature of an electro- 

 dynamometer, to give a good steady idiostatic 

 potential gauge, by which the constant of any 

 electrometer or ordinary galvanometer may be 

 easily and accurately tested. That is an object to 

 be sought ; there are plenty of ways of obtaining 

 it, and I hope, before another year has passed, to 

 see it realised in many ways, certainly in one way. 





