WILLIAM SIEMENS, F.R.S. 321 



liminary step, ask the Government to be represented on the In- 

 ternational Metrical Commission, whose admirable establishment 

 \ res possesses, independently of its practical work, consider- 

 able scientific interest, as a well-found laboratory for developing 

 methods of precise measurement ? 



Next in importance to accurate measures of length, weight, 

 and time, stand, for the purposes of modern science, those of 

 electricity. 



The remarkably clear lines separating conductors from non- 

 conductors of electricity, and magnetic from non-magnetic sub- 

 stances, enable us to measure electrical quantities and effects 

 with almost mathematical precision ; and, although the ultimate 

 nature of this, the youngest scientifically investigated form of 

 energy, is yet wrapt in mystery, its laws are the most clearly 

 established, and its measuring instruments (galvanometers, elec- 

 trometers, and magnetometers; are amongst the most accurate 

 in physical science. Nor could any branch of science or industry 

 be named in which electrical phenomena do not occur, to exercise 

 their direct and important influence. 



If, then, electricity stands foremost amongst the exact sciences, 

 it follows that its unit measures should be determined with the 

 utmost accuracy. Yet, twenty years ago, very little advance had 

 been made towards the adoption of a rational system. Ohm had, 

 it is true, given us the fixed relations existing between electro- 

 motive force, resistance and quantity of current ; Joule had 

 established the dynamical equivalent of heat and electricity, and 

 Gauss and Weber had proposed their elaborate system of absolute 

 magnetic measurement. But these invaluable researches appeared 

 only as isolated efforts, when, in 1862, the Electric Unit Com- 

 mittee was appointed by the British Association, at the instance 

 of Sir William Thomson, and it is to the long-continued activity 

 of this committee that the world is indebted for a consistent and 

 practical system of measurement, which, after being modified in 

 details, received universal sanction last year by the International 

 Electrical Congress assembled at Paris. 



At this congress, which was attended officially by the leading 

 physicists of all civilised countries, the attempt was successfully 

 made to bring about a union between the statical system of 

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