130 REPORT — 1893. 



U.S.A., who were well qualified by their scientific attainments to represent 

 the opinion of their respective countries. 



It appeared from the discussion that a few comparatively slight 

 modifications of the resolutions included in our pi'evious report would 

 tend to secure international agreement. 



An extract from the report of the Electrical Standards Committee of 

 the British Association embodying the results of this discussion was 

 communicated to us by the Secretary, and will be found in the appendix 

 to this report. 



Having carefully reconsidered the whole question in view of this 

 communication, and having received the report of the sub-committee 

 mentioned in resolution 14 of our previous report, we now desire, for the 

 resolutions contained in that report, to substitute the following : — 



Resolutions. 



1. That it is desirable that new denominations of standards for the 

 measurement of electricity should be made and approved by her Majesty 

 in Council as Board of Trade standards. 



2. That the magnitudes of these standards should be determined 

 on the electro-magnetic system of measurement with reference to the 

 centimetre as unit of length, the gramme as unit of mass, and the second 

 as unit of time, and that by the terms centimetre and gramme are meant 

 the standards of those denominations deposited with the Board of Trade. 



3. That the standard of electrical resistance should be denominated 

 the ohm, and should have the value 1,000,000,000 in terms of the centi- 

 metre and second. 



4. That 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 centi- 

 metres, may be adopted as 1 ohm. 



5. That a material standard, constructed in solid metal, should be 

 adopted as the standard ohm, and should from time to time be verified 

 by comparison with a column of mercury of known dimensions. 



6. That, for the purpose of replacing the standard, if lost, destroyed, 

 or damaged, and for ordinary use, a limited number of copies should be 

 constructed, which should be periodically compared with the standard 

 ohm. 



7. That resistances constructed in solid metal should be adopted as 

 Board of Trade standards for multiples and sub-multiples of the ohm. 



8. That the value of the standard of resistance constructed by a com- 

 mittee of the British Association for the Advancement of Science in the 

 years 1863 and 1864, and known as the British Association unit, may be 

 taken as '9866 of the ohm. 



9. That the standard of electrical current should be denominated the 

 ampere, and should have the value one-tenth (0"1) in terms of the centi- 

 metre, gramme, and second. 



10. That an unvarying current which, when passed through a solution 

 of nitrate of silver in water, in accordance with the specification attached 

 to this report, deposits silver at the rate of O'OOlllB of a gramme per 

 second may be taken as a current of 1 ampere. 



11. That an alternating current of 1 ampere shall mean a current 



