PRACTICAL STANDARDS FOR ELECTRICAL MEASUREMENTS. 



43 



It is evident from these observations that a difference of -OlOj per 

 cent, exists, or that — 



Kesistance of Reichsanstalt unit — Resistance of Laboratory unit 



= •000105 ohm 



Comparison of the Unit of Resistance employed at the Board of Trade 

 and that of the Laboratory. 



(A) 



The comparison of these two units is not so complete. Two platinum- 

 silver units and one of manganin have been determined at both labora- 

 tories. The measurements taken at Teddington indicate that no change 

 resulted during the journeyings of the coils. In addition one 1,000-ohm 

 coil (Nalder 6863) has been determined. 



Table XII. — Residts of Measurements of various coils at the Board of Trade 

 Offices and at the Laboratory, February and March 1903. 



The exact relationship between the B.O.T. unit and that of the 

 Laboratory is therefore still incomplete. It seems fairly certain however 

 that— 



Resistance of Laboratory unit— Resistance of B.O.T. unit 



= -00006 ohm, a difference of 'OOe per cent. . . (B) 



From the two relationships — 



Resistance of Reichsanstalt unit — Resistance of N.P.L, unit 



= •000105 ohm 

 Resistance of Laboratory unit — Resistance of B.O.T. unit 

 5= -00006 ohm 

 we have 



Resistance of Reichsanstalt unit— Resistance of B.O.T. unit 



= 000165 ohm, a difference of "0165 per cent. , . (C) 



The present values of the B.A. coils are as follows : — 



Table XIIL 



