ON STANDARDS FOR USE IN ELECTRICAL MEASUREMENTS. 



127 



Experiments for Improving the Construction of Practical Standards 

 for Electrical Measurements. — Report of the Committee, con- 

 sisting of Professor Carey Foster {Chairman), Lord Kelvin, 

 Professors Ayrton, J. Perry, W. G. Adams, Lord Kayleigh, and 



0. J. Lodge, Drs. John Hopkinson and A. Muirhead, Messrs. 

 W. H. Preece and Herbert Taylor, Professor J. D. Everett, 

 Professor A. Schuster, Dr. J. A. Fleming, Professors G. F. 

 FitzG-erald, Cf. Chrystal, and J. J. Thomson, Messrs. E. T. 

 G-LAZEBROOK {Secretary), W. N. Shaw, and T. C. Fitzpatrick, 

 Dr. J. T. Bottomley, Professor J. Viriamu Jones, Dr. Gr. John- 

 stone Stoney, Professor S. P. Thompson, and Mr. G. Forbes. 



APPENDIX . ^■*-*^^ 



1. Siij>/>le>iie»fari/ Report of the. Electrical Standards Committee of the 



Board of trade . ' 129 



II. Experiments on the Effects of the Heating produced in the Coils hy the 



Currents used in Testinrj. By R. T. GlAZEBEOOK .... 136 



III. On Standards of Low Electrical Resistance. By J. Viriamu Jones . 137 



The work of testing resistance coils at the Cavendish Laboratory has 

 been continued. A table of the coils tested is given. They have 

 all been ' ohms,' as defined by the resolution of the Committee given in 

 their last report, and since adopted by the Board of Trade Committee on 

 electrical standards in the following form : — 



The resistance offered to an unvarying electric current by a column 

 of mercury at the temperature of melting ice 14-4521 grammes in mass, of 

 a constant cross-sectional area, and of a length of 106-3 centimetres, may 

 be taken as 1 ohm. The relation between the B.A. unit and the ohm is 

 the following : — 



1 B.A.U.=-9866 ohm. 



' This coil had been tested before. 



