E. L. Nichols — Allot/* <>/ Ft rrchJUatigaru a and Copper. 471 



Art. LV. — 7% Electrical Resietana qf ifu Alloys of Ferro- 

 ManaaneSi and Copper; (From determinations made by 

 Mr. i>. EL Blood) ; by Edward L. Nichols. 



[Contributions from the Physical Laboratory of Cornell University, No. 6.] 



Tx the selection of a material for standards of electrical 

 resistance, the influence of temperature upon the conductivity 

 of the wire to be used in their construction is a factor of prime 

 importance. Since the report of the British Association Com- 

 mittee (1807) on electrical standards, no great progress has 

 been made in this matter. The manufacturers of German 

 silver and of similar alloys have, it is true, succeeded in reduc- 

 ing considerably the temperature-coefficients of their metals ; 

 so that it is now possible to obtain wires the resistance of 

 which changes less than two hundredths of one per cent per 

 degree Centigrade. Such a variation is, however, by no means 

 negligible in operations of precision ; and the coefficient of 

 different wires, even when made from the same metal, vary 

 greatly. In a single resistance box, as has been shown by 

 Professor Anthony, one may have coils which are well adjusted 

 at some one temperature but to which, no single temperature- 

 correction will apply.* On this and on many other accounts, 

 the discovery of an alloy, the resistance of which is unaffected 

 by temperature is a matter of some importance. 



In 1888 patents were granted by the United States govern- 

 ment, for two new alloys to be used in the construction of re- 

 sistance coils.f The properties claimed for these alloys were 

 so remarkable — complete freedom from change of resistance 

 upon heating in the one case and a decrease of resistance with 

 rise of temperature, in the other — that in the absence of more 

 complete data concerning them than are contained in the 

 patent office specifications, it seemed to me a matter of some 

 importance to subject them to a detailed experimental inves- 

 tigation. 



The necessary experiments were undertaken at my sugges- 

 tion by Mr. B. H. Blood, and it is upon his results that the 

 following statements are based. X 



* W. A. Anthony: On the Differing Temperature Coefficients of the Different 

 Coils of a fine Rheostat. Transactions of the American Institute of Electrical 

 Engineers, vol. iv, p. 137. 



f See Edward Weston, U. 8. patents, Nos. 381,304 and 381,305 ; Specifications 

 and Drawings of Patents. April 17, 1888, p. 1507. Also Official Gazette of the 

 IT. S. Patent Office, vol. xliv, p. 339. 



\ B. H. Blood : Temperature Coefficients of Ferro-manganese-Copper Alloys, 

 Thesis (in MS.); Library of Cornell University. 1889. 



