On the Electric Conducting Power of Copper and its Alloys. 547 

 Table II. 



Composition ac- 

 cording to 

 Messrs. Johnson 

 and Matthey. 



Analyses of Alloy. 



Specific Conductivity. 



Values found by 

 Professor Thomson. 



Values found by 

 myself. 



Published 

 Values. 



Redetermined 

 Values. 



Pure copper elec- 

 trotype from 

 Messrs. De la 

 Rue 







107 at 9° 



107-2 at 10° 



Ditto from 

 Messrs. Elking- 

 ton and Co. . . 



► All not fused. 





107-5 at 12° 



105-9 at 10°-5 



Ditto from Mr. 

 Matthews 







108-7 at 12° 



106-9 at 14° 



Ditto, my own. . 



j .. .. 





107-7 at 12° 



108-1 at 10° 



All the above wires were hard-drawn. On looking at the above, 

 we find that pure copper conducts better than any of the alloys. 



With regard to the analyses, the quantity of each specimen was 

 so small that they could not be checked by repetition ; they, how- 

 ever, approach very closely to the composition assigned to them by 

 Messrs. Johnson and Matthey (with the exception of the suboxide). 

 The traces of iron will be due to the draw-plates. I will now make 

 a few remarks on the above results. 



I. That copper containing # 25 per cent, of silver conducts better 

 than that with - 13 per cent., may be explained by assuming that the 

 first contains less suboxide than the second ; for it is very possible 

 that copper containing silver will not absorb suboxide so readily as 

 the purer metal. It must also be borne in mind that the copper em- 

 ployed for making these alloys was in all probability simply electro- 

 type copper (not fused), and that the suboxide therefore was ab- 

 sorbed during the process of fusing the two metals together. This 

 assumption explains how it is that the alloys contain almost the same 

 amount of impurity as was originally alloyed with the copper ; for 

 had the copper employed contained suboxide, we should have ex- 

 pected to have found greater differences in the cases of the tin, lead, 

 and zinc alloys, as some portion of those metals would have been ox- 

 idized at the expense of part of the suboxide of copper, and escaped 

 as oxide to the surface of the melted metal. 



II. That copper containing 0*25 per cent, tin conducts better 

 than that containing 0'13 per cent., may also be explained by 

 assuming that they absorbed different amounts of suboxide during 

 the process of fusion ; for although tin, in presence of suboxide of 

 copper, would be oxidized, yet copper retains the suboxide so 

 tenaciously, that portions will always remain with the copper. 



III. The fact that the conducting powers of the alloy of copper 



