88 POPULAR LECTURES AND ADDRESSES. 



were both present at the Conference, and they 

 joined heartily in the proposal to adopt an 

 absolute system, but the question was how to 

 make a beginning ; and the answer adopted by 

 the Conference was to ask for a definition of 

 an absolute system in terms of a column of 

 mercury. The column of mercury was the one 

 standard in existence, that could be reproduced 

 otherwise than by merely copying from one wire 

 to another ; and it was naturally adopted as the 

 foundation upon which a standard, if not a 

 practical unit to be used, should be founded. In 

 short, then, the finding of the Conference was 

 to this effect : that as soon as good evidence is 

 given of a sufficiently near measurement for 

 practical purposes, of the resistance of any con- 

 ductor be it a piece of wire or a column of 

 mercury as soon as such measurement should 

 be made, with evidence that it is accurate enough 

 for practical purposes, then the unit which the 

 British Association had aimed at should be 

 adopted ; but it was to be left to the judgment 

 and the convenience of the users of standards 



