ON STANDARDS FOR USE IN ELEC'IRICAL MEASTREMENT8. 137 



Order in Council regarding Standards /or Electrical Measurements. 



At the Court at Onhorne Hovse, Isle of Wight, Auf/vst 23, 1894. 

 Prwent : The Queen's Most Excellent Majesty in dmncil. 



Whereas by 'The Weights and Measures Act, 1889,' it is among other 

 things enacted that the Board of Trade shall from time to time cause such 

 new denominations of standards for the measurement of electricity as 

 appear to them to be required for use in trade to be made and duly 

 verified. 



And whereas it has been made to appear to the Board of Trade that 

 new denominations of standards are required for use in trade based upon 

 the following units of electrical measurement, viz. — 



1. The ohm, which has the value 10^ in terms of the centimetre and 

 the second of time, and is represented by the I'esistance 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. 



2. The ampere, which has the value )'„ in terms of the centimetre, 

 the gramme, and the second of time, and which is represented Ijy the 

 unvarying electric current which when passed through a solution of 

 nitrate of silver in water in accordance with the specification appended 

 hei-eto, and marked A, deposits silver at the rate of O'OOlllS of a gramme 

 per second. 



3. The volt, which has the value 10* in terms of the centimetre, the 

 gramme, and the second of time, being the electrical pressure that if 

 steadily applied to a conductor whose resistance is one ohm will produce 

 a current of one ampere, and which is represented by -6974 (|yf}^) of the 

 electrical pressure at a temperature of 15° C. between the poles of the 

 voltaic cell known as Clark's cell set up in accordance with the specification 

 appended hereto, and marked B. 



And whereas they have caused the said new denominations of stan- 

 dards to be made and duly verified. 



Now, therefore, her Majesty, by virtue of the power vested in her 

 by the said Act, by and with the advice of her Privy Council, is pleased 

 to approve the several denominations of standards set forth in the 

 schedule hereto as new denominations of standards for electrical measureT 

 luent. C. L. Peel. 



Schedule. 



I. — Standard of Electrical Resistance. 



A standard of electrical resistance denominated one ohm being the 

 resistance between the copper terminals of the instrument marked ' Board 

 of Trade Ohm Standard Verified, 1894,' to the passage of an unvarying 

 electrical current when the coil- of insulated wire forming part of the 

 aforesaid instrument and connected to the aforesaid terminals is in all 

 parts at a temperature of 15° '4 C. 



II. Standard of Electrical Current. 



A standard of electrical current denominated one ampere being the 

 current which is passing in and through the coils of wire forming part of 

 the instrument marked 'Board of Trade Ampere Standard Verified, 1894,' 

 when on reversing the current in the fixed coils the change in the forces 



