546 Royal Society :— 



investigate the subject, in order to ascertain the cause of these dif- 

 ferences. For this purpose Professor Thomson kindly placed at my 

 disposal all his alloys ; and in the following Table I will give the 

 results of the analyses and redeterminations of the conducting power 

 of his set. The wires were in some cases very faulty, so that I was 

 obliged to draw them finer ; others drew so badly, that the values ob- 

 tained could not very well agree with those already published. After 

 having measured their resistances, I sent them back to Prof. Thom- 

 son for redetermination. Table I. gives the results so obtained, 

 taking the alloy containing 99*75 copper and '25 silver=100; and 

 Table II. the values found for some specimens of pure copper : — 

 Table I. 



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. 



Copper 99-75.. 

 Silver 0-25 



Silver 0-24 p. c. 



traces of iron 

 Suboxide of copper 



}>oo { 



100-1 

 99-9 



100-37 at 17°* 

 99-73 at 17° 



Copper 99-87.. 

 Silver 0-13 



Silver 0-13 p. c. 



traces of iron 

 Suboxide of copper 



I 100-7 \ 



95-8 

 95-8 



95-44 at 17°8 

 94-58 at 17°-8 



Copper 99-75.. 

 Lead 0-25 .... 



Lead 0-2 per cent. 



traces of iron 

 Suboxide of copper 



I 103-9 \ 



102-7 

 103-1 



102-80 at 17° 

 102-G2 at 17°-6 



Copper 99-75.. 

 Tin 0-25 



Tin 0-23 per cent. 



traces of iron 

 Suboxide of copper 



I 94-G 1 



100-7 

 101-0 



99-89 at 18° 

 98-27 at 16°-4 



Copper 99-87.. 

 Tin 013 



Tin 0-07 per cent. 



traces of iron. 

 Suboxide of copper 



I 9G-0 \ 



97-7 



98-5 



97-79 at 18° 

 97-62 at 18° 



Copper 99-2 . . 

 Zinc 0-8 



Zinc, with traces of 

 iron, 1-06 per cent. 



| 90-2 | 



91-3 



88-5 



94-71 at 15°-4 

 90-67 at 15°-6 



Copper 98-6 

 Zinc 1-4 



Zinc, with traces of 

 iron, l*47per cent. 



} « { 



81-1 

 80-1 



81-15 at 16°-8 

 80-13 at 17°-7 



Copper 98-2 . . 

 Zinc 1-8 



Zinc, with traces of 

 iron, l - 75 percent. 



} - { 



77-9 



78-5 



77-8 at 16°-4 

 78-0 at 17° 



Pure copper . . 



Contained suboxide 

 of copper 



1 100 



98-6 





Copper 99-87.. 

 Lead 0-13 .... 





J 104-7 







* Compared with a hard-drawn gold-silver wire of equal diameter and length, 

 whose conducting power is equal at 0° C. to 100, these values would be G03 - 7 

 and 600-5. (See my paper " On an Alloy which may be used as a Standard of 

 Electrical Resistance," Phil. Mag. Feb. 1861.) 



