ELECTRICAL MEASUREMENT. 445 



in one respect is a happy one, although there is 

 something to be said on the other side, the unit 

 adopted by Messrs. Siemens, founded on the 

 measurement of a certain column of mercury 

 the Siemens unit produced and reproduced in 

 their accurate resistance coils approaches some- 

 what nearly to the unit which in Weber's system 

 would be io 9 or a thousand million centimetres 

 per second. This is so far convenient that 

 measurements in Siemens units are very easily 

 reduced to the absolute measure. The committee 

 of the British Association, of which our President 

 was one and I also had the honour to be a 

 member, proposed a method of measurement 

 which was carried out chiefly by Professors Clerk 

 Maxwell, Balfour Stewart and Fleeming Jenkin, 

 who laid down what is called the British Associa- 

 tion unit of resistance, to which the name of 

 " Ohm," according to the advice of Mr. Latimer 

 Clark, was given in commemoration of one of 

 the great founders of electro-magnetic science. 

 Ohm being the man who gave us first the law 

 of currents in connection with electro-motive force 



